Application Note
AN_348
FT51A FT800 Sensors Sample
Version 1.1
Issue Date: 2015-11-26
This document provides a guide for using the FT51A development
environment to display sensor readings on an FT800 display.
Use of FTDI devices in life support and/or safety applications is entirely at the user’s risk, and the
user agrees to defend, indemnify and hold FTDI harmless from any and all damages, claims, suits
or expense resulting from such use .
Future Technology Devices International Limited (FTDI)
Unit 1, 2 Seaward Place, Glasgow G41 1HH, United Kingdom
Tel.: +44 (0) 141 429 2777 Fax: + 44 (0) 141 429 2758
Web Site: http://ftdichip.com
Copyright © 2015 Future Technology Devices International Limited
Application Note
AN_348 FT51A FT800 Sensors Sample
V ers ion 1 .1
D oc ument Reference N o.: FT _001127
C learance N o.: FT DI# 4 3 1
Table of Contents
1 Introduction ............................................................ 3
1.1 Overview.......................................................................... 3
1.2 Features........................................................................... 3
1.3 Limitations ....................................................................... 3
1.4 Scope ............................................................................... 3
2 Firmware Overview ................................................. 4
2.1 FT800 Display................................................................... 4
2.2 FT51A Libraries ................................................................ 4
3 FT800 Sensors Firmware ......................................... 5
3.1 Timer ............................................................................... 5
3.2 Writing to FT800 .............................................................. 6
3.3 Sensor Reading Acquisition ............................................... 6
3.3.1
Force Sensor .......................................................................................................... 6
3.3.1
Heart Rate Sensor.................................................................................................. 7
3.3.2
Temperature Sensor............................................................................................... 8
4 Possible Improvements ........................................... 9
5 Contact Information .............................................. 10
Appendix A – References ........................................... 11
Document References ............................................................ 11
Acronyms and Abbreviations .................................................. 11
Appendix B – Revision History.................................... 12
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AN_348 FT51A FT800 Sensors Sample
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D oc ument Reference N o.: FT _001127
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1 Introduction
This application note documents an example firmware project for the FT51A. The source code is
available in the “examples\ AN_348_FT51A_FT800_Sensors_Sample” folder of the FT51A Software
Development Kit.
1.1 Overview
The readings from sensors on the FT51A EVM board are displayed on an FT800 display module.
The display shows heart rate, temperature and force readings both numerically and graphically.
The hardware modules required to use the application note are a VM800B module (FT800 and
display) and a FT51A EVM module. The sensors are built-in to the FT51A EVM module.
The FT800 on the VM800B module is connected to the SPI Master interface of the FT51A on pins
DIO_2 (Slave Select 1), DIO_3 (SPI MOSI), DIO_4 (SPI MISO) and DIO_5 (SPI SCLK).
1.2 Features
The FT800 Sensors Sample has the following features:
-
Open source firmware.
Reads data from a temperature sensor (ADT7310) using the SPI Master interface.
Converts the analogue voltage from a force sensor to a digital reading.
Detects transitions on an analogue voltage input to make a simple heart rate monitor.
Displays output on FT800 display via the SPI Master interface.
1.3 Limitations
The firmware does not implement a USB device to transmit data to a host. It does not implement
Device Firmware Update (DFU) on the USB.
1.4 Scope
The guide is intended for developers who are creating applications, extending FTDI provided
applications or implementing example applications for the FT51A.
In the reference of the FT51A, an “application” refers to firmware that runs on the FT51A;
“libraries” are source code provided by FTDI to help user, access specific hardware features of the
chip.
The FT51A Tools are currently only available for Microsoft Windows platform and are tested on
Windows 7 and Windows 8.1.
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2 Firmware Overview
The sensors firmware reads inputs from the sensors on the FT51A EVM board and converts these
into values to display. It employs similar methods to those used in AN_347 FT51A Test and
Measurement Sample Application Note.
2.1 FT800 Display
The VM800B module interface for displaying the graphics and text is configured over t he SPI
Master interface. Commands and data to send are stored in a buffer in RAM and sent in batches to
the FT800 device on the VM800B module at regular intervals. The SPI Master interface is shared
with the temperature sensor – the Slave Select lines of the SPI Master interface are used to
address the FT800 or the temperature sensor.
The firmware includes an FT800 abstraction layer providing functions which are used to perform
actions on the FT800. This layer is in the ft_gpu directory of the sample source code. The
definition of FT51A_PLATFORM and FT51A_PLATFORM_SPI in the file FT_Platform.h are used to enable
the FT51A abstraction in the libraries and use SPI for the communications. The same library can be
used for other FTDI microcontrollers.
2.2 FT51A Libraries
The firmware uses the SPI Master library, general config library and the IOMUX library. The IOMUX
library is used in the example code to set the output characteristics of the SPI Master interface. A
code module for the ADT7310 temperature sensor (via the SPI Master library) is included.
The firmware is designed for the FT51A EVM module and may be extended to use the LCD for
displaying some information. If so, then it will need the I2C Master library added.
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3 FT800 Sensors Firmware
The firmware included in the example code demonstrates reading sensors and displaying on an
FT800 controlled display.
The firmware is designed for the FT51A EVM module. It will use the force sensor, temperature
sensor and heart rate sensor. The force and heart rate sensors use an analogue voltage input
which is converted using the ADC features. The temperature sensor uses a n ADT7310 temperature
sensor which is connected to the FT51A via an SPI bus.
All sensor readings and screen drawing triggers are initiated by timers in the
Force_Heartrate_Temperature function in ft800_demo_board.c. This function contains a while loop
that does not exit.
3.1 Timer
A timer is used to provide delays and time measurements for implementing polling intervals.
The first timer ms_timer is used to create general purpose delays, for instance when resetting the
temperature sensor.
Each of the three sensors has a timer timer_force, timer_pulse and timer_temp. These timers
operate independently. There is also a timer to update the FT800 disp lay called timer_display.
void ms_timer_interrupt(const uint8_t flags)
{
(void) flags; // Flags not currently used
if (ms_timer)
{
ms_timer--;
}
if (timer_display)
{
timer_display--;
}
if (timer_force)
{
timer_force--;
}
if (timer_pulse)
{
timer_pulse--;
}
if (timer_temp)
{
timer_temp--;
}
// Reload the timer
TH0 = MSB(MICROSECONDS_TO_TIMER_TICKS(1000));
TL0 = LSB(MICROSECONDS_TO_TIMER_TICKS(1000));
}
void ms_timer_initialise(void)
{
// Register our own handler for interrupts from Timer 0
interrupts_register(ms_timer_interrupt, interrupts_timer0);
// Timer0 is controlled by TMOD bits 0 to 3, and TCON bits 4 to 5.
TMOD &= 0xF0; // Clear Timer0 bits
TMOD |= 0x01; // Put Timer0 in mode 1 (16 bit)
// Set the count-up value so that it rolls over to 0 after 1 millisecond.
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TH0 = MSB(MICROSECONDS_TO_TIMER_TICKS(1000));
TL0 = LSB(MICROSECONDS_TO_TIMER_TICKS(1000));
TCON &= 0xCF; // Clear Timer0's Overflow and Run flags
TCON |= 0x10; // Start Timer0 (set its Run flag)
}
3.2 Writing to FT800
Commands to the FT800 can either be sent discretely to registers or to internal RAM in batches
when the display is being constantly updated by the firmware.
Both methods will enable the SPI Master to talk to the FT800 with the Slave Select 1 (SS1) line
going high before sending commands. The next stage is to send an address of the register or area
of RAM to be addressed in the FT800. The data for the register or RAM follows before SS1 is de asserted to signal the end of the transfer.
A discrete register change is performed using the FT800_Write08 or FT800_Write16 functions in
the file ft800_demo_board.c. These functions call the hardware abstraction layer functions to turn
on slave select and send the register commands before turning off slave select.
Batches of commands will be stored in a RAM buffer on the FT51A called Ft_CmdBuffer (the size
and therefore the end offset of this buffer are held in the variable Ft_CmdBuffer_Index). Helper
functions FT800_CmdBuffer_AddCmd and FT800_CmdBuffer_AddStr functions are available to abstract
the operation of the buffer.
When the batch is complete the commands are sent to the FT800 RAM u sing the
FT800_CmdBuffer_Send function. The size of Ft_CmdBuffer is 4 kB.
Instructions for an entire screen update can be stored in the buffer before being transmitted to the
FT800 at a fixed interval. The update is triggered when the timer_display value reaches zero at
which point all current sensor readings are formatted and the commands to create the screen
update are generated.
This document does not deal with the FT800 commands used to render the graphics on the
display.
3.3 Sensor Reading Acquisition
Each sensor is read from the firmware’s main loop, in the Force_Heartrate_Temperature function.
3.3.1
Force Sensor
When the timer_force reaches zero, a new ADC is triggered and the timer restarted. The ADC
conversion will take place in the background and an interrupt generated when it is complete.
if (timer_force == 0)
{
IO_REG_INTERRUPTS_WRITE(IO_CELL_SAMPLE_0_7_1, MASK_IO_CELL_0_SAMPLE);
timer_force = FORCE_TIMER;
}
The ADC interrupt handler (section below) will update the sampleValueForce and sampleReadyForce
variables when the reading is complete.
IO_REG_INTERRUPTS_READ(IO_CELL_INT_0_1, interrupt);
// FSR Output
if (interrupt & MASK_SD_CELL_0_INT)
{
IO_REG_INTERRUPTS_READ(IO_CELL_0_ADC_DATA_L_1, sample_l);
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IO_REG_INTERRUPTS_READ(IO_CELL_0_ADC_DATA_U_1, sample_h);
sampleValueForce = ((sample_h << 8) | sample_l);
sampleReadyForce = TRUE;
// Clear ADC interrupt register bit
IO_REG_INTERRUPTS_WRITE(IO_CELL_INT_0_1, MASK_SD_CELL_0_INT);
}
The main loop will arrive back at the force sensor code and update the force reading when the
sampleReadyForce flag is set by the interrupt handler.
if (sampleReadyForce)
{
sampleReadyForce = FALSE;
if (sampleValueForce > 900)
{
sampleValueForce = 900;
}
force = sampleValueForce;
}
The timer_force will continue to run until the next sample is due.
3.3.1
Heart Rate Sensor
When the timer_pulse reaches zero, a new ADC is triggered and the timer restarted. The ADC
conversion will take place in the background and an interrupt generated when it is complete.
if (timer_pulse == 0)
{
IO_REG_INTERRUPTS_WRITE(IO_CELL_SAMPLE_8_15_1, MASK_I O_CELL_10_SAMPLE);
timer_pulse = PULSE_TIMER;
}
The ADC interrupt handler will update the sampleValuePulse and sampleReadyPulse variables when
the reading is complete.
IO_REG_INTERRUPTS_READ(IO_CELL_INT_1_1, interrupt);
// Pulse Rate
if (interrupt & MASK_SD_CELL_10_INT)
{
IO_REG_INTERRUPTS_READ(IO_CELL_10_ADC_DATA_L_1, sample_l);
IO_REG_INTERRUPTS_READ(IO_CELL_10_ADC_DATA_U_1, sample_h);
sampleValuePulse = ((sample_h << 8) | sample_l);
sampleReadyPulse = TRUE;
// Clear ADC interrupt register bit
IO_REG_INTERRUPTS_WRITE(IO_CELL_INT_1_1, MASK_SD_CELL_10_INT);
}
The main loop will arrive back at the heart rate sensor code and update the heart beat reading
when the sampleReadyPulse flag is set by the interrupt handler.
if (timer_pulse == 0)
{
IO_REG_INTERRUPTS_WRITE(IO_CELL_SAMPLE_8_15_1, MASK_IO_CELL_10_SAMPLE);
timer_pulse = PULSE_TIMER;
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}
if (sampleReadyPulse)
{
sampleReadyPulse = FALSE;
pulseSamples[pulseIndexer] = sampleValuePulse;
// Keep track of how many samples in a block are greater than threshold ...
if (sampleValuePulse >= PULSE_THRESHOLD)
{
pulseCounter++;
// Mark as a heart beat if number of samples in a block exceeds set value
if (pulseCounter == PULSE_IS_BEAT)
{
// Set top bit (bits 0-9 contain the actual sensor value)
pulseSamples[pulseIndexer] |= 0x8000;
// Start looking for the next heart beat ...
pulseCounter
= 0;
LED_HR_ON();
}
}
else
{
LED_HR_OFF();
// Deal with gaps (value < threshold) when counting of samples in a block
if (pulseCounter > 0)
{
pulseCounter--;
}
}
pulseIndexer = (++pulseIndexer) % PULSE_SAMPLES;
}
The loop fills a buffer with PULSE_SAMPLES number of samples with the top bit being set if a
sequence of consecutive samples is above a threshold. The size of this buffer is calculated to hold
15 seconds worth of samples.
This buffer is parsed in the RenderPulse function where the measured heart rate is calculated and
graphics are created to show a ‘paper chart’ history of detected pulses.
3.3.2
Temperature Sensor
An SPI bus is used to measure the temperature from an ADT7310 sensor connected to the SPI
Master interface. When the timer_temp reaches zero the timer is reset and an SPI Master read is
performed to the ADT3710.
if (timer_temp == 0)
{
// Read the temperature from the SPI Master
sampleValueTemp = temperature_read();
timer_temp = TEMP_TIMER;
}
The temperature is returned in units of 0.01 °C.
The temperature sensor library will assert Slave Select 0 (SS0) to a logic high to enable the
ADT7310 device during SPI Master Transfers.
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4 Possible Improvements
This implementation of the heart rate sensor has a simpler method of calculation than the meth od
used in AN_347 FT51A Test and Measurement Sample Application Note.
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5 Contact Information
Head Office – Glasgow, UK
Branch Office – Tigard, Oregon, USA
Future Technology Devices International Limited
Unit 1, 2 Seaward Place, Centurion Business Park
Glasgow G41 1HH
United Kingdom
Tel: +44 (0) 141 429 2777
Fax: +44 (0) 141 429 2758
Future Technology Devices International Limited
(USA)
7130 SW Fir Loop
Tigard, OR 97223-8160
USA
Tel: +1 (503) 547 0988
Fax: +1 (503) 547 0987
E-mail (Sales)
E-mail (Support)
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E-Mail (Support)
E-Mail (General Enquiries)
[email protected]
[email protected]
[email protected]
Branch Office – Taipei, Taiwan
Branch Office – Shanghai, China
Future Technology Devices International Limited
(Taiwan)
2F, No. 516, Sec. 1, NeiHu Road
Taipei 114
Taiwan , R.O.C.
Tel: +886 (0) 2 8791 3570
Fax: +886 (0) 2 8791 3576
Future Technology Devices International Limited
(C hina)
Room 1103, No. 666 West Huaihai Road,
Shanghai, 200052
C hina
Tel: +86 21 62351596
Fax: +86 21 62351595
E-mail (Sales)
E-mail (Support)
E-mail (General Enquiries)
E-mail (Sales)
E-mail (Support)
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[email protected]
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[email protected]
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[email protected]
Web Site
http://ftdichip.com
Distributor and Sales Representatives
Please visit the Sales Network page of the FTDI Web site for the contact details of our distributor(s) and sales
representative(s) in your country.
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performanc e requirements. A ll application-related information in this document (including application des c riptions , s ugges ted
FT D I devic es and other materials ) is provided for referenc e only. While FT D I has taken c are to as s ure it is ac c urate, this
information is s ubject to c ustomer c onfirmation, and FT D I dis c laims all liability for s ys tem des igns and for any applic ations
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us er agrees to defend, indemnify and hold harmles s FTDI from any and all damages , c laims , s uits or expens e res ulting from
s uc h us e. T his doc ument is s ubject to c hange without notic e. N o freedom to us e patents or other intellectual property rights is
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des c ribed in this doc ument, may be adapted or reproduc ed in any material or electronic form without the prior written c ons ent
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Appendix A – References
Document References
FTDI MCU web page: http://www.ftdichip.com/MCU.html
USB Test and Measurement Class specification:
http://www.usb.org/developers/docs/devclass_docs/USBTMC_1_006a.zip
IVI Foundation: http://www.ivifoundation.org/
SCPI specification: http://www.ivifoundation.org/docs/scpi-99.pdf
USB Device Firmware Update Class specification:
http://www.usb.org/developers/docs/devclass_docs/DFU_1.1.pdf
Acronyms and Abbreviations
Terms
Description
HID
Human Interface Device
MTP
Multiple Time Program – non-volatile memory used to store program code
on the FT51A.
USB
Universal Serial Bus
USB-IF
USB Implementers Forum
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Appendix B – Revision History
Document Title:
AN_348 FT51A FT800 Sensors Sample
Document Reference No.:
FT_001127
Clearance No.:
FTDI# 431
Product Page:
http://www.ftdichip.com/FTProducts.htm
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Revision
Changes
Date
1.0
Initial Release
2014-12-12
1.1
Update FT51 references to FT51A
2015-11-26
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