AN4300
Application note
Advanced light control and diagnostics using
SPC56xBx and SPC56xCx microcontrollers
Introduction
The members of the SPC56xBx and SPC56xCx families are high performance
microcontrollers developed for car body application needs. These devices are especially
useful in automotive light management applications and offer features to assist the car body
system developer in writing optimized firmware with a very low CPU load.
This document offers an interesting example about the interconnection between the eMIOS,
CTU, and ADC modules of the SPC56EC74 (one member of the SPC56xB/Cx family) in a
lighting application, including the support of circuitry diagnostics, without placing an
additional load on the MCU’s CPU. This example is easily applied to each device of the
SPC56xB/Cx family.
September 2013
DocID024675 Rev 2
1/40
www.st.com
Contents
AN4300
Contents
1
2
3
Lighting application design challenge . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1
General light application aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2
Driver signals characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3
System proposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4
Diagnosis check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4.1
Digital diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4.2
Analog diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4.3
Serial diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
SPC56xBx features to cover lighting needs . . . . . . . . . . . . . . . . . . . . . 11
2.1
eMIOS (enhanced Modular Input/Output Subsystem) . . . . . . . . . . . . . . . .11
2.2
CTU (Cross Triggering Unit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3
ADC (Analog-to-Digital Converter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Lighting application example architecture . . . . . . . . . . . . . . . . . . . . . . 14
3.1
Hardware architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1.1
3.2
Software Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2.1
4
Synchronous diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3
Synchronous Analog Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.4
Implementation of the synchronous diagnosis . . . . . . . . . . . . . . . . . . . . . 19
MCU initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.1
Setting up Mode Entry and clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2
DSPI configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3
eMIOS_0 and EMIOS_1 modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.3.1
eMIOS_0 and eMIOS_1 module initialization . . . . . . . . . . . . . . . . . . . . 22
4.4
DMA module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.5
ADC module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.5.1
2/40
Generalities on M0-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Check Voltage Battery function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.6
CTU module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.7
Micro Resources summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
DocID024675 Rev 2
AN4300
5
Contents
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Appendix A Reference documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
A.1
Reference documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
A.2
Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
DocID024675 Rev 2
3/40
3
List of tables
AN4300
List of tables
Table 1.
Table 2.
Table 3.
4/40
Resources allocated on the microcontroller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
DocID024675 Rev 2
AN4300
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Lamp light bulb characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
System solution for light application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Light management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
eMIOS, ADC and CTU interconnection scheme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
eMIOS-OPWMT mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Lighting application—example system concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
SPC56EC74L7 Minimodule + M0-6 Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Initial Configuration flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Vbat measurement and duty-cycle update flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Delay between the CS_Sync and Output channel/Current Sense signal . . . . . . . . . . . . . . 19
MC_Mode_Init function7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
PLL initialization function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
DSPI master init function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
eMIOS init function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
eMIOS clock init function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
eMIOS_0 configuration code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
eMIOS_1 Ch23 and Ch0 configuration code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
eMIOS_1 Ch1 and Ch2 configuration code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
eMIOS_1 Ch25, Ch26 and Ch 17 configuration code . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
eMIOS_1 Ch18 configuration code. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Init DMA Vbat function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
SPI_Vbat_SetTCD function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
initDMA_1 function part 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
initDMA_1 function part 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
init DMA_1 function part 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
ADC init function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
ADC_0 CH0 EoC interrupt service routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Check Voltage Battery function part1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Check Voltage Battery function part2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
bctu_init function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
DocID024675 Rev 2
5/40
5
Lighting application design challenge
AN4300
1
Lighting application design challenge
1.1
General light application aspects
In an automotive lighting application it is necessary to drive two types of lights:
1.
Bulb lamp
2.
LED
When controlling the lamp light bulb, two points must be addressed:
•
Lamp power supply variations
•
Lamp lifetime
Lamp power supply voltage may differ when compared to its nominal value. Figure 1
displays how lamp lifetime depends on power supply voltage. The impact of 5 %
overvoltage (630 mV at 12.6 V) on light bulb performance is significant, as indicated by the
vertical line in the figure. The light bulb luminous flux grows up to 120 % and the light bulb
lifetime is reduced to less than 60 %, when compared to nominal values. Therefore, the
lamp power supply voltage should be regulated to the nominal value to maintain lamp
lifetime. The most common control technique is the PWM, which can also be used for lamp
light beam intensity control.
Figure 1. Lamp light bulb characteristics
A lamp’s lifetime is limited and it can be shortened if the lamp is connected in a faulty
environment. If the design includes lamp diagnostics and protection, the lamp’s nominal
lifetime can be preserved. Usually the load drivers report various diagnosis information and
the light application has to collect and check this information. These factors must be taken in
account when designing a lighting module.
6/40
DocID024675 Rev 2
AN4300
1.2
Lighting application design challenge
Driver signals characteristics
The signals that drive the light loads must satisfy the following requirements:
•
Capability to drive up to 60 channels with PWM signals
•
Capability to drive different load types using PWM signals with different characteristics:
–
Bulb lamp
PWM frequency: ~100 Hz
Duty cycle: 50 to 100 %
Duty cycle adjustment precision: usually 5 %
–
LED
PWM frequency: 150 to 200 Hz
Duty cycle: 10 % to 100 % (as much as 2 % to 100 % for high efficiency LED)
Duty cycle adjustment precision: usually 1–2 %
The variation of the duty cycle is performed to maintain constant power on the lamps when
the battery voltage changes.
The duty cycle variation is based on the following expression:
Equation 1
δ =
V ref
Vbat
2
If V b a t > V re f
2
where
Vref is the nominal value of the battery voltage
Vbat is the actual battery voltage
If Vbat ≤ Vref, the duty cycle is equal to 100 %, else the expression is applied. The adaptation
of the duty cycle is performed one time per period.
A typical battery voltage value for automotive applications is 13.2 V, so if, for example, the
application reads a Vbat equal to 16 V, a duty cycle of 68 % applies.
When turning the lamp light bulb on, the bulb current applied to a cold filament can reach up
to 10 times the rated current. The total current of several lamps causes a significant power
supply voltage drop and an increase in the electromagnetic interference (or EMI) emissions.
Therefore, it is essential not to drive all lamps together and it is necessary to introduce a
delay between each pair of rising edges of the PWM signals (see Figure 3).
1.3
System proposal
In a typical system solution for a light application, the SPC56xB/Cx microcontroller family
can manage several power drivers, depending on how the power is managed and the
number of channels to be driven.
Some devices are driven by an SPI link. Using this link, the application can configure the
signals, that are generated inside the driver device, to drive the loads.
DocID024675 Rev 2
7/40
39
Lighting application design challenge
AN4300
Other devices need an input signal (PWM signals) for each load to generate the output
signal to drive the loads.
It is possible to use both the microcontroller and the power devices for the solution shown in
Figure 2. This solution is configured with an STMicroelectronics power driver and the
SPC56EC74 microcontroller.
Figure 2. System solution for light application
9EDW
9
3:0LQSXWVLJQDOV
9UHJ
63,
63&(&
'LDJQRVWLF
91'([[[
63,
914
9EDW
("1(3*
This system uses devices that are driven by PWM input signals and other devices that use
an SPI connection to configure the drivers.
1.4
Diagnosis check
Today’s requests for automotive systems are based not only upon technical features and
reliability, but also upon increasingly important safety concepts. To fulfill these requirements,
a system must provide and communicate feedback on its behavior to external devices. This,
in turn, makes it possible to detect faults and react to them in a specified time.
The power drivers used in light applications provide diagnostic signals that give information
about the status of loads driven. These signals must be read and interpreted to give
feedback to the application. It is important to understand if there are faults and to execute
protective action to obtain a safe and robust system.
Three different diagnosis types exist:
•
Digital
•
Analog
•
Serial
The diagnosis types are explained in the following sections.
8/40
DocID024675 Rev 2
AN4300
1.4.1
Lighting application design challenge
Digital diagnosis
To read the digital diagnosis it is necessary to read an I/O pin of the driver for each load
driven. To read this type of diagnosis the microcontroller has to read the digital pin in polling
mode or by connecting this signal to an external interrupt line.
1.4.2
Analog diagnosis
To read the analog diagnosis a current sense pin is available for each load driven. This pin
is used to read a proportional current (voltage using a resistor) that flows in the load.
Comparing this current with certain thresholds can determine if problems on the load exist.
To read the voltage of the current sense pin, an analog-to-digital conversion must be
performed.
The analog diagnosis has to be read in synchronous mode to the input (PWM) signal which
is available after a delay from the rising edge of the input signals. The analog-to-digital
conversion has to be triggered with a delay from the rising edge of the input signals to allow
the load current to stabilize.
1.4.3
Serial diagnosis
When the power devices provide serial diagnosis, they usually save the type of fault in
internal registers. The microcontroller, using the SPI link, then performs a query on the
specified register to examine the fault status.
The application can perform the following types of diagnosis inspection:
•
•
During T_ON (time when the PWM input signal is switched on) of the input signal
–
Open-load
–
Overtemperature
–
Undervoltage
–
Short-circuit to GND
–
Short-circuit to VCC
During T_OFF (time when the PWM signal is switched off) of the input signal
–
Open-load
–
Short-circuit to VCC
The digital and serial diagnosis can usually be read asynchronously with respect to the
PWM input signals and the diagnosis action can be performed during a noncritical instant of
the system cycle. The CPU load used to collect this information is not an important aspect.
The analog diagnosis consists of checking the current that flows in the loads. The input
signal status must be known to collect diagnosis information in a specific instant of the
loads’ activity. The reading of the diagnosis and the input signal must be synchronized to
determine the status of the input signal.
The input signal is a PWM signal, making it necessary to select if the diagnosis is occurred
in the T_ON or T_OFF phase of the input signal. Furthermore, a delay exists between the
rising (falling) edge and the instant when the diagnosis read occurs because the current
sense signal is stabilized only after a transitory time (about 300 µs).
DocID024675 Rev 2
9/40
39
Lighting application design challenge
AN4300
Figure 3. Light management
SHULRGQ
SHULRGQ
+]FKDQQHO Q
&K
&K
&K
&K
&KQ
&KQ
+]FKDQQHO Q
SHULRGQ
SHULRGQ
SHULRGQ
&K
&K
&K
&K
&KQ
&KQ
("1(3*
The SPC56xBx and SPC56xCx devices offer dedicated features to cover the light
application requirements with very low CPU load, especially when the analog diagnosis has
to be managed. Section 2: SPC56xBx features to cover lighting needs describes the device
features that are used to manage the analog diagnosis.
10/40
DocID024675 Rev 2
AN4300
2
SPC56xBx features to cover lighting needs
SPC56xBx features to cover lighting needs
The SPC56EC74 is a member of the SPC56xBx and SPC56xCx 32-bit microcontroller unit
family. It operates at speeds of up to 120 MHz and provides a variety of peripherals (DSPI,
IIC, ADC, CTU, eMIOS, FlexCAN, LINFlex) balanced with relatively large Flash, RAM, and
emulated EEPROM memory.
The following modules are essential parts of the lighting application suitable for lamp bulb as
well as for LED control:
•
eMIOS (enhanced Modular I/O Subsystem)—provides functionality to generate or
measure time events and then to generate PWM signals
•
CTU (Cross Trigger Unit)—allows triggering analog-to-digital conversion synchronized
to a PWM signal
•
ADC—allows converting analog signals synchronized to a PWM signal and allows
holding the converted value in different register for each ADC channel
The three module descriptions are covered in Section 2.1: eMIOS (enhanced Modular
Input/Output Subsystem) Section 2.2: CTU (Cross Triggering Unit) and Section 2.3: ADC
(Analog-to-Digital Converter). It is also recommended to read the SPC56xBx and
SPC56xCx device reference manual see Section Appendix A: Reference documents.
The eMIOS channels are connected to event configuration registers of the CTU, where it
links an eMIOS trigger to a specified ADC channel conversion (see Figure 4). Inside each
event configuration, that is connected in a fixed way to an eMIOS channel, it is possible to
write an ADC channel that is triggered when an event from the eMIOS channel arrives.
Figure 4. eMIOS, ADC and CTU interconnection scheme
&78
H0,26$&K
H0,26$&K
(YHQW&RQILJXUDWLRQ5HJ
(YHQW&RQILJXUDWLRQ5HJ
H0,26
H0,26%&KQ
(YHQW &RQILJXUDWLRQ5HJ $'&
$'&&RQWURO
H0,26)/$*FOHDU
7ULJJHU2XWSXW
&RQWURO
$'&
$'&&RQYHUVLRQ
("1(3*
2.1
eMIOS (enhanced Modular Input/Output Subsystem)
The SPC56EC74 includes two identical eMIOS modules that together provide up to 64
channels with input and output capability. Each eMIOS module provides 32 channels with
OPWMT mode, especially suited for the lighting application. In OPWMT mode, a channel is
in PWM mode, making it possible to configure a compare match, anywhere in the period, to
trigger—using the CTU—an analog-to-digital conversion at a specified point of the period.
This is especially suited for lighting applications.
DocID024675 Rev 2
11/40
39
SPC56xBx features to cover lighting needs
AN4300
When configuring channels UC[0], UC[8], UC[16], UC[23], and UC[24] in modulus Counter
Mode (MC), the A1 register determines the counting period.
Figure 5. eMIOS-OPWMT mode
When configuring a channel in OPWMT mode, the channel can be linked to:
•
Internal counter (only for the channels that have this feature)
•
Counter bus A driven by UC[23]
•
Counter buses B, C, D, E driven by UC[0], UC[8], UC[16], UC[24]
In a channel configured in OPWMT mode, the A1 register value defines the PWM leadingedge and the B1 register value defines the PWM trailing edge (duty cycle). The A2 register
is the sampling point for diagnostic purposes (the ADC channel trigger using the CTU), and
in B2, the buffered value of the trailing edge, which is, on A1 match, loaded into the B1
register (see the eMIOS chapter of the device reference manual see Section Appendix A:
Reference documents). When the B2 value equals the A1 value, the PWM duty cycle is
0 %. When a B2 value is higher than the channel period, the PWM duty cycle reaches
100 %. The PWM output signal polarity is dependent on the user’s choice.
When configuring channels UC[0], UC[8], UC[16], UC[23] and UC[24] in Modulus Counter
(MC) mode, the A1 register determines the counting period.
2.2
CTU (Cross Triggering Unit)
When the eMIOS OPWMT channel counter reaches the A2 value, the specific ADC channel
conversion is initiated by the CTU module. The ADC channel number is specified in the
CTU event configuration register by the user. When configuring the event configuration
register, be aware, that:
•
The CTU channel 0–15 event can trigger any of the ADC channels 0–15
•
The CTU channel 32-47 event can trigger any of the ADC channels 32–47
•
The CTU channel 48–95 event can trigger any of ADC channels 48–95
For more details, see the Cross Triggering Unit chapter in the device reference manual (see
Section Appendix A: Reference documents).
12/40
DocID024675 Rev 2
AN4300
2.3
SPC56xBx features to cover lighting needs
ADC (Analog-to-Digital Converter)
The 2 ADC module convert analog signals into digital form; ADC_0 with a 10-bit resolution
and ADC_1 with a 12-bit resolution offering normal, injected and trigger-injected modes.
The ADC module can be configured to provide up to 62 single-ended input channels with no
additional external logic, exapandable to 90 channels using an external multiplexer, all
driven by the ADC module logic.
When using the SPC56EC74:
•
The ADC channels 0–15 correspond to ANP pins 0–15 with a resolution of 10-bit or 12bit (depending on the choice of ADC_0 (10-bit resolution) or ADC_1 (12-bit resolution);
in both cases the used pins are the same (precision channels)
•
The ADC_0 channels 32–60 (28 channels) correspond to ANS pins 0–27 (extended
channel, medium occurrence) while the ADC_1 channels 32-44 corresponf to ANS pins
0-12
•
The ADC channels 64–95 correspond to ANX pins 0–3 (external multiplexer driven by
MA0–2 ADC pins; external channel, medium accuracy)
For the family SPC56xB/Cxx, 6 + 3 analog watchdogs (6 on 10-bit ADC, 3 on 12-bit ADC)
are present on the ADC peripheral.
The analog watchdogs provide the capability to generate an interrupt for continuous
hardware monitoring to determine if the converted channel value lies within a given guarded
area defined by user-specified threshold values. If the converted value lies outside the
guarded area, an interrupt is generated. The analog watchdog interrupts are well suited for
light bulb diagnostic purposes.
With SPC56xB/Cxx devices, the diagnosis value can be collected in hardware mode, thus
reducing the load on the CPU for this task. Moreover, one time within an input signal period,
a load is placed on the CPU when these values collected in hardware mode are checked
and when they are compared to certain thresholds.
The analog watchdog feature can reduce this CPU load by triggering an interrupt only when
a fault occurs, instead of one time for the period, because the diagnosis check is performed
in automatic mode.
DocID024675 Rev 2
13/40
39
Lighting application example architecture
3
AN4300
Lighting application example architecture
The lighting application example code introduces essential SPC56EC74 initialization and
configuration for demonstrating eMIOS and ADC synchronization using the CTU. An
example is based on the LA system study depicted in Figure 6 that is suitable for lamp bulb
as well as for LED control.
Figure 6. Lighting application—example system concept
The demonstration is based on the SPC56EC74L7 176LQFP EVB, and the application code
is written in C language using the Green Hills compiler.
The purpose of the application code is show how the external triggering capability of Bolero
device brings “system” advantage in highly complex body application such as:
• Minimal microcontroller resources required
• Low Interrupt and CPU load
• Minimized usage of Memory resources
• Few ADC channels and pins needed
The example application code has been implemented using the M0-6 Mother board for
Power PC applications connected with the SPC56EC74L7 minimodule and the EVB using
the J1 connector on the board following the connection reported in Figure 6. and in Figure 7.
14/40
DocID024675 Rev 2
AN4300
Lighting application example architecture
Figure 7. SPC56EC74L7 Minimodule + M0-6 Board
3.1
Hardware architecture
The hardware system as described in the Figure 6 uses:
• The same DSPI channel (DSPI_0) to drive all the M0-6 devices
• A dedicated chip select for each M06 device
• A PWM channel (EMIOS Channel) shared for all M06 devices to provide a common time
base (M06 Clock)
• Four eMIOS channels configured in SAIC to manage the trigger signals
• An ADC channel for each M06 device shared for the four channels inside the same M06
device.
3.1.1
Generalities on M0-6
As power devices we have used the STMicroelectronics M06 devices:
• VNQ6040S
• VNQ6004S
These devices are made using STMicroelectronics VIPower technology. They are intended
for driving resistive or inductive loads directly connected to ground. Devices are protected
against voltage transient on Vcc pin. Programming, control and diagnostics are
DocID024675 Rev 2
15/40
39
Lighting application example architecture
AN4300
implemented via the SPI Bus through the dedicated pins. Each device offers four channels
that can drive different loads in term of power.
3.2
Software Implementation
The software implements the following features:
Support of the SPI configuration of 16 channel of four M06
Adapt the PWM signal to drive the loads to the V_bat variations
Collect the current sense values for each channel and for each period
Low CPU load to collect the Current Sense
The code allows to initialize the configuration of M06 devices and at the beginning of each
period (10 msec) performs the following steps:
Vbat Measurement via ADC
Duty cycle update for all channels of M06 devices
SPI frame for new information configuration
Digital diagnosis on all M06 devices
3.2.1
Synchronous diagnosis
Figure 8 and Figure 9 represent the initial configuration of the Microcontroller and the Vbat
measurement strategy in order to update the duty-cycle of the PWM signal.
16/40
DocID024675 Rev 2
AN4300
Lighting application example architecture
Figure 8. Initial Configuration flowchart
DocID024675 Rev 2
17/40
39
Lighting application example architecture
AN4300
Figure 9. Vbat measurement and duty-cycle update flowchart
3.3
Synchronous Analog Diagnosis
The reading of the current sense is done in a synchronous way with the M06 output signals.
In the following application code, current sense is read during TON of the period, 300 usec
after CS_sync rising edge. It should be noticed that the microcontroller has to be
synchronized with the outputs of the M06 device.
18/40
DocID024675 Rev 2
AN4300
Lighting application example architecture
Figure 10. Delay between the CS_Sync and Output channel/Current Sense signal
Depending on Vbat values, M06 can be either in PWM mode or in DC mode. In the former
case synchronous diagnosis is triggered by the rising edge of the CS_Sync signal for each
active channel, by an internal timer expiration (e.g. 10 msec) of the micro in the latter.
3.4
•
When in PWM mode, the CS_Sync signals is used to trigger the ADC conversion of the
Current Sense of a channel after a 300 usec delay from its rising edge.
•
The End of Conversion of the ADC activates a DMA channel that transfers the ADC
value from the peripheral register to a SRAM location.
•
At the end of a period all Current Sense are available to the same memory structure.
Implementation of the synchronous diagnosis
In order to trigger ADC conversions to perform analog diagnosis synchronous with external
events (CS_sync arrival) the following resources of the microcontroller have been used:
•
A Channel of the eMIOS is configured as Input Capture
•
The arrival of the input signal on the Input Capture triggers a DMA transfer intended to
trigger a second eMIOS channel previously configured as SAOC (Single Action Output
Compare mode) counting 300 usec
•
The SAOC End of Counting event triggers another eDMA transfer triggering the ADC
conversion.
After the conversion the following action are performed:
•
The end of ADC conversion triggers a DMA transfer moving the ADC values to a buffer
in RAM.
•
Via channel linking, a DMA transfer sends an SPI frame to a given M0-6 in order to link
the multiplexer to the next current sense/CS_Sync.
DocID024675 Rev 2
19/40
39
MCU initialization
4
AN4300
MCU initialization
In this section are described the most significant functions used in the application example
code.
4.1
Setting up Mode Entry and clocks
This module enables clocks to all peripherals and sets the 12 MHz bus clock using the PLL.
Figure 11. MC_Mode_Init function7
20/40
DocID024675 Rev 2
AN4300
MCU initialization
Figure 12. PLL initialization function
The PA[0] pin is configured as Clock output in order to verify the clock bus frequency
provided by the PLL. The CGM module allows to tune the dividers in order to provide a clock
source of 12MHz starting from an external oscillator of 40 MHz.
4.2
DSPI configuration
The following function allows to initialize the DSPI module used for the SPI transmission.
It configures the DSPI_0 as master and the following pins as:
•
Pad PA[12] as DSPI_0 SIN (Serial input)
• Pad PA[13] as DSPI_0 SOUT (Serial output)
• Pad PA[14] as DSPI_0 SCK (Serial Communication Clock)
• Pad PA[15] as DSPI_0 PCS0 (Peripheral Chip Select_0)
• Pad PF[10] as DSPI_0 PCS1 (Peripheral Chip Select_1)
• Pad PF[11] as DSPI_0 PCS2 (Peripheral Chip Select_2)
• Pad PE[06] as DSPI_0 PCS3 (Peripheral Chip Select_3)
The CTAR register defines the following parameters:
• Set Double Baud rate disabled
• Frame size equal to 16
• Baud Rate Prescaler value equal to 3
• Baud Rate Scaler equal to 4
• Delay after Transfer Scaler equal to 32
DocID024675 Rev 2
21/40
39
MCU initialization
AN4300
• PCS to SCK delay prescaler equal to 7
Figure 13. DSPI master init function
4.3
eMIOS_0 and EMIOS_1 modules
4.3.1
eMIOS_0 and eMIOS_1 module initialization
The following function allows to configure the two eMIOS and the following pins as:
• Set PCR[1] as E0UC[1] using PA[1]
• Set PCR[89] as E1UC[1] using PF[9]
• Set PCR[112] as E1UC[2] using PH[0]
• Set PCR[92] as E1UC[25] using PF[12]
• Set PCR[93] as E1UC[26] using PF[13]
• Set PCR[104] as E1UC[17] using PG[8]
• Set PCR[105] as E1UC[18] using PG[9]
22/40
DocID024675 Rev 2
AN4300
MCU initialization
Figure 14. eMIOS init function
Figure 15. eMIOS clock init function
For eMIOS_1, the bus clock is divided by one in the system clock prescaler, while for
eMIOS_0 the prescaler is set to 12.
EMIOS_0 Ch23 is configured in MC to drives the Bus A with a period of 1 msec, due to the
value of 1000 used as PWM_PERIOD.
eMIOS_0 CH1 is configured in SAOC mode, with an internal counter period of 300 usec.
DocID024675 Rev 2
23/40
39
MCU initialization
AN4300
Figure 16. eMIOS_0 configuration code
eMIOS_1 CH23, configured in MC, drives bus A with a period of 19.417 usec (51.5 KHz)
eMIOS_1 CH0, configured in MC, drives bus B with a period of 10 msec (100 Hz)
eMIOS_1 CH1 is configured in OPWMT driven by bus A (51.5 KHz) with a duty cycle of 50%
to give the PWM clock to M06 devices.
eMIOS_1 CH2 is configured in OPWMT driven by bus B, with the same period of the PWM
generated by M06 devices (100 Hz) and it is used to give an internal counter to check the
Vbat once for each period or to trigger the collection of the diagnosis collection when the
M06 devices work in DC mode.
eMIOS_1 CH17 is configured in SAIC mode and it is connected to the Sync_mux of the
M06_3. Internally it triggers DMA_MUX 21.
eMIOS_1 CH18 is configured in SAIC mode and it is connected to the Sync_mux of the
M06_4. Internally it triggers DMA_MUX 22.
eMIOS_1 CH25 is configured in SAIC mode and it is connected to the Sync_mux of the
M06_1. Internally it triggers DMA_MUX 23.
eMIOS_1 CH26 is configured in SAIC mode and it is connected to the Sync_mux of the
M06_2. Internally it triggers DMA_MUX 24.
24/40
DocID024675 Rev 2
AN4300
MCU initialization
Figure 17. eMIOS_1 Ch23 and Ch0 configuration code
Figure 18. eMIOS_1 Ch1 and Ch2 configuration code
DocID024675 Rev 2
25/40
39
MCU initialization
AN4300
Figure 19. eMIOS_1 Ch25, Ch26 and Ch 17 configuration code
Figure 20. eMIOS_1 Ch18 configuration code
26/40
DocID024675 Rev 2
AN4300
4.4
MCU initialization
DMA module
The initDMA_Vbat function permits to configure DMA channel number 6 to be used to
transfer, by SPI, the configuration to M06 devices about the PWM waves generation.
This DMA channel is configured to be triggered by DSPI0_TX signal each time when Vbat is
read and PWM configuration is needed.
The scatter gather feature allows to change the TCD descriptor to send the duty-cycle
configuration for 16 channels, for all M06 (4 channels for 4 M06) and it allows to change the
TCD descriptor to wait the new manual trigger to send M06_PWM control register for the
next period.
Figure 21. Init DMA Vbat function
The function SPI_Vbat_SetTCD allows to create a TCD structure for the SG_PWM vectors
0 and 1 and for the DMA channel 6.
DocID024675 Rev 2
27/40
39
MCU initialization
AN4300
Figure 22. SPI_Vbat_SetTCD function
The function InitDMA_1 configures the eDMA channels to collect the diagnosis
automatically. For this reason the following channels are configured as described below:
• DMA CH0, CH7, CH8 and CH9 are configured to trigger the start counter of the
eMIOS0_CH1 when the SYNC_MUX comes from M06_1, M06_2, M06_3 and M06_4
respectively.
• DMA CH1 is configured to trigger the stop of counter of the eMIOS0_CH1
• DMA CH1 is linked to DMA CH2. In this way when the CH1 finishes it starts the DMA CH2
transmission which allows the start of the ADC conversion.
• DMA CH5 is configured to send, by SPI, the configuration to the MUX for the active M06
to select the right channel connected to the CS and with CS_SYNC.
• DMA CH4 is configured to transfer the value of the 4 Data Registers relative to the 4 ADC
channels linked to the 4 M06 to a buffer in the memory, This is done each trigger because
it is necessary to read all ADC channels that can trigger DMA transfers.
• DMA CH10 is configured to transfer the value converted by ADC to the final RAM
structure. The scatter gather feature is used to change the TDC to adapt the ADC Data
Register and Memory location relative to the M06 Channel selected.
28/40
DocID024675 Rev 2
AN4300
MCU initialization
Figure 23. initDMA_1 function part 1
DocID024675 Rev 2
29/40
39
MCU initialization
AN4300
Figure 24. initDMA_1 function part 2
30/40
DocID024675 Rev 2
AN4300
MCU initialization
Figure 25. init DMA_1 function part 3
4.5
ADC module
The dadc_init function initializes ADC module enabling the CTU trigger. It selects the ADC
channels used for the conversion. ADC_0 CH0 is used to convert the VBat and a End of
Conversion interrupt is set on this channel.
EMIOS1_CH2 is used as counter to read Vbat. When this counter elapses, the CTU_CH34
(connected to eMIOS1_CH2) will trigger the ADC_0 CH0 to convert the Vbat.
At the EoC an interrupt will be raised to adapt the Duty Cycle of the PWM signals to the
Vbat.
DocID024675 Rev 2
31/40
39
MCU initialization
AN4300
Figure 26. ADC init function
32/40
DocID024675 Rev 2
AN4300
MCU initialization
Figure 27. ADC_0 CH0 EoC interrupt service routine
4.5.1
Check Voltage Battery function
This function is called inside the EOC interrupt of the ADC, when the conversion is triggered
by the CTU and only for the ADC0_CH0.
It performs a reading on the Vbat value and carries out the duty cycle of the PWM signals
update.
The voltage read with a nominal value of the Battery voltage (13.2 V) is equal to:
13,2*4,7/(4,7+22) =2,32V with a resistor divider of 22KOhm and 4.7 KOhm
The resolution of the ADC is:
5V/1024=4,88mV
Reporting this resolution to the value of the Battery using the resistor divider:
4.88*(4,7+22)/4,7 = 28,404 mV
that is the resolution of voltage of the battery (V_BAT_RESOLUTION)
Vref
2
When the value is read, following the relation δ = ---------------2- :
Vbat
if Vref>= Vbat then the battery voltage is under than nominal (13,2 V) value and the output
channels of the M06 devices are configured in DC mode (100% Duty Cycle) and the trigger
to read the diagnosis is given manually with the same period used to read the Vbat.
If Vref<Vbat the battery voltage is upper than the nominal value and the output channels of
the M06 devices are configured in PWM mode with Duty Cycle based on the above relation.
The trigger, in order to read the diagnosis, is given by the Sync_Mux signal from each M06
device.
After that the table of PWM signals are updated and these values are sent to each M06
devices using the SPI connection.
DocID024675 Rev 2
33/40
39
MCU initialization
AN4300
Figure 28. Check Voltage Battery function part1
34/40
DocID024675 Rev 2
AN4300
MCU initialization
Figure 29. Check Voltage Battery function part2
4.6
CTU module
The bctu_init function configures the CTU channels as follow;
CTU CH34 is connected to the eMIOS1_CH2 and it is configured to trigger the ADC
conversion of the ADC0_CH0.
DocID024675 Rev 2
35/40
39
MCU initialization
AN4300
Figure 30. bctu_init function
4.7
Micro Resources summary
The Lighting Application example allocates the several resources inside the micro:
Table 1. Resources allocated on the microcontroller
Peripheral
name
36/40
Resource
Notes
DSPI
DSPI_0
7 pins
INTC
IRQ 62
IRQ 0
ADC_EOC
Software interrupt
eDMA
CH6-Vbat measure
CH0 - Start counter M06-1
CH7-Start counter M06-2
CH8 - Start counter M06-3
CH9 - Start counter M06-4
CH1 Start ADC conversion
CH4 Transfer data register of ADC in RAM
CH10 Transfer value in final array
CH5 Trigger SPI communication to select the M06
channel
10 DMA channels used
eMIOS
eMIOS0 - 2 Channels
eMIOS1 - 8 Channels
10 eMIOS channels
used
DADC
CH0 for Vbat
CH1, CH2, CH3, CH4 to convert the CS
5 ADC channels used
BCTU
CTU_CH34
eMIOS1_CH2 vs ADC0_CH0
1 CTU channel used
DocID024675 Rev 2
AN4300
5
Conclusion
Conclusion
The SPC56EC74 lighting application example introduces MCU eMIOS, CTU, and ADC
modules usage within a lighting application, which is in this case well suited for the lamp
light bulbs control as well as for the lamp LEDs control with no major change required in the
peripheral’s software.
The benefit of using the CTU module is significant as opposed to using the timer to trigger
ADC at a certain point within a PWM channel cycle. The timer produces frequent interrupts
that need to be processed by the MCU CPU, causing an increase in the CPU load and
suspending run time processes. Using the CTU gives the application designer a powerful
tool to avoid diagnostic timer-configuration challenges and makes the lighting application
simpler to design and test.
The ADC module gives the designer the opportunity to use watchdog threshold interrupts to
increase MCU performance, and enables fast responses in case of lamp light bulb failures.
If required, the number of the ADC channels can be increased from 64 up to 95, using
simple external logic circuitry fully controlled by the ADC module.
The eMIOS module offers up to 64 PWM channels suitable for a lighting application as well
as for other PWM-based applications. The eMIOS module provides PWM channels with
high resolution and flexibility.
The lighting application example consists of an example description and complete software
demonstration based on the SPC56EC74L7 LQFP176 minimodule and EVB.
This example is easily portable to each device of the SPC56xB/Cxx family; for devices
which have DMA module, no particular modifications are required. For devices where DMA
module is missing, the DMA feature can be replaced with interrupt routines but with a higher
CPU load.
DocID024675 Rev 2
37/40
39
Reference documents
Appendix A
A.1
A.2
AN4300
Reference documents
Reference documents
•
SPC560B4x, SPC560B5x, SPC560C4x, SPC560C5x, 32-bit MCU family built on the
embedded Power Architecture® (RM0017), available at www.st.com
•
SPC564Bxx, SPC56ECxx 32-bit MCU family built on the embedded Power
Architecture® (RM0070 DOC ID18196)
Acronyms
Table 2. Acronyms
Acronym
ADC
Analog to Digital Converter
ALTCADR
eMIOS UC A2 Register
CADR
eMIOS UC A1 Register
CBDR
eMIOS UC B2 Register
CTU
Cross Triggering Unit
EMC
Electromagnetic Compatibility
eMIOS
EVB
Configurable enhanced Modular I/O Subsystem
Evaluation Board
LA
Lighting Application
MC
eMIOS channel Modulus Counter mode
MCU
OPWMT
Microcontroller Unit (SPC560B50)
eMIOS channel Output PWM mode with Trigger
PCR
Pad Configuration Register
PWM
Pulse Width Modulation
SIUL
System Integration Unit Lite
SAIC
Single Action Input Capture
SAOC
Single Action Output Compare
DMA
UC
38/40
Name
Direct Memory Access
eMIOS Universal Counter channel
DocID024675 Rev 2
AN4300
Revision history
Revision history
Table 3. Document revision history
Date
Revision
Changes
13-Jun-2013
1
Initial release
17-Sep-2013
2
Updated Disclaimer.
DocID024675 Rev 2
39/40
39
AN4300
Please Read Carefully:
Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the
right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any
time, without notice.
All ST products are sold pursuant to ST’s terms and conditions of sale.
Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no
liability whatsoever relating to the choice, selection or use of the ST products and services described herein.
No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. If any part of this
document refers to any third party products or services it shall not be deemed a license grant by ST for the use of such third party products
or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoever of such
third party products or services or any intellectual property contained therein.
UNLESS OTHERWISE SET FORTH IN ST’S TERMS AND CONDITIONS OF SALE ST DISCLAIMS ANY EXPRESS OR IMPLIED
WARRANTY WITH RESPECT TO THE USE AND/OR SALE OF ST PRODUCTS INCLUDING WITHOUT LIMITATION IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS
OF ANY JURISDICTION), OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT.
ST PRODUCTS ARE NOT DESIGNED OR AUTHORIZED FOR USE IN: (A) SAFETY CRITICAL APPLICATIONS SUCH AS LIFE
SUPPORTING, ACTIVE IMPLANTED DEVICES OR SYSTEMS WITH PRODUCT FUNCTIONAL SAFETY REQUIREMENTS; (B)
AERONAUTIC APPLICATIONS; (C) AUTOMOTIVE APPLICATIONS OR ENVIRONMENTS, AND/OR (D) AEROSPACE APPLICATIONS
OR ENVIRONMENTS. WHERE ST PRODUCTS ARE NOT DESIGNED FOR SUCH USE, THE PURCHASER SHALL USE PRODUCTS AT
PURCHASER’S SOLE RISK, EVEN IF ST HAS BEEN INFORMED IN WRITING OF SUCH USAGE, UNLESS A PRODUCT IS
EXPRESSLY DESIGNATED BY ST AS BEING INTENDED FOR “AUTOMOTIVE, AUTOMOTIVE SAFETY OR MEDICAL” INDUSTRY
DOMAINS ACCORDING TO ST PRODUCT DESIGN SPECIFICATIONS. PRODUCTS FORMALLY ESCC, QML OR JAN QUALIFIED ARE
DEEMED SUITABLE FOR USE IN AEROSPACE BY THE CORRESPONDING GOVERNMENTAL AGENCY.
Resale of ST products with provisions different from the statements and/or technical features set forth in this document shall immediately void
any warranty granted by ST for the ST product or service described herein and shall not create or extend in any manner whatsoever, any
liability of ST.
ST and the ST logo are trademarks or registered trademarks of ST in various countries.
Information in this document supersedes and replaces all information previously supplied.
The ST logo is a registered trademark of STMicroelectronics. All other names are the property of their respective owners.
© 2013 STMicroelectronics - All rights reserved
STMicroelectronics group of companies
Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan Malaysia - Malta - Morocco - Philippines - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America
www.st.com
40/40
DocID024675 Rev 2