DLP-TEMP-G

DLP-TEMP-G
USB / Data-Acquisition Module
NOW LEAD-FREE
Features:
•
•
•
•
3 Digital I/Os, 3 Analog Inputs (0-5 Volts) or any combination
USB 1.1 and 2.0 Compatible Interface
4th Generation Silicon from FTDI
Supports Up To 3 Digital Temperature Sensors
Applications:
•
•
Data Acquisition
Temperature Monitoring
INTRODUCTION
The DLP-TEMP-G is a USB/microcontroller based 3-channel data-acquisition system
preprogrammed with firmware for digital I/O or reading digital temperature-sensing devices. The
DLP-TEMP-G board is equipped with a Type A male USB connector for direct connection to a
USB port. No cable is required unless the board is to be located away from the PC, in which
case a user supplied USB A-A (male-female) extension cable can be used.
The digital temperature-sensing device supported is the Dallas Semiconductor DS18B20. Three
of these sensors can be monitored simultaneously while connected to the DLP-TEMP-G via
Category 5 cable at distances up to 200 feet. (For instruction on how to connect the sensors to
the DLP-TEMP-G via Category 5 cable, refer to the Application section of this document.) All
power for the DLP-TEMP-G’s circuitry and DS18B20 temperature sensors is taken from the USB
port so no external power source is required.
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The microcontroller used is the PIC12F683, 8-pin, Flash-based microcontroller from Microchip.
As mentioned above, the 12F683 is preprogrammed for analog voltage measurement and for
reading the digital temperature sensors, but it can also be erased and reprogrammed with user
code if desired. Reprogramming the micro requires a user-supplied device programmer. (Refer
to the schematic at the end of this document for the pin out of the programming header.)
The microcontroller uses a single port pin and a pull-up resistor to communicate with each digital
temperature sensor. Refer to the DS18B20’s datasheet for a complete description of its
communications protocol. The firmware for the DLP-TEMP-G was written in C and can be
downloaded from dlpdesign.com.
USB INTERFACE
The USB interface was implemented using the FT232RL USB-UART IC from FTDI. This device
connects to the host computer via the Type A USB (male) connector and supports the 8 standard
RS232 serial signals. Only the TX and RX signals are used on the DLP-TEMP-G board and are
all that is required to form a serial connection to the host computer. Since handshaking is not
used in this design, the firmware in the 12F683 processor must be ready to accept all incoming
serial data from the host computer or the data will be lost.
In order for the DLP-TEMP-G (and FT232RL) to receive incoming serial data from the host,
FTDI’s VCP (Virtual Com Port) drivers must be installed. The driver installation process is
initiated by simply plugging the DLP-TEMP-G into a USB port. The driver installation wizard will
prompt for the location of the drivers files (in a folder or on a floppy) and will copy the required
files to the proper destination such that the next time the board is connected the driver files will be
automatically loaded without prompting the user. The VCP driver files can be downloaded for
free from dlpdesign.com or ftdichip.com.
Once the drivers are loaded and the com port number for the DLP-TEMP-G is set in Device
Manager, the application program running on the host simply opens what it thinks is an RS232
port (9600, N, 8, 1) and begins communicating with the 12F683 microcontroller.
COMMUNICATIONS PROTOCOL
For this design, a rather simplistic protocol was selected in an attempt to present the design in as
basic a way as possible. Single-byte commands are used to communicate with the 12F683
microcontroller. The following table shows the command list:
COMMAND
12F683 Response
R (read and convert)
Send back 18 bytes of data from the sensors and start another
temperature conversion in both sensors. Provided as legacy
support for compatibility with the original DLP-TEMP.
P (ping)
Echo the letter ‘Q’ back to the host. Provided as legacy support
for compatibility with the original DLP-TEMP.
S
Read temperature sensor at S1, return data and convert
2
T
Read temperature sensor at S2, return data and convert
U
Read temperature sensor at S3, return data and convert
A
Setup S1/AN2/GP2 for analog, read voltage and return 2 bytes
B
Setup S2/AN0/GP0 for analog, read voltage and return 2 bytes
C
Setup S3/AN3/GP4 for analog, read voltage and return 2 bytes
Example host voltage read code:
//declare tx[] and rx[] buffers
tx[0] = 'A';
PutBuffer(tx, 1);//send tx out serial port – substitute your serial port code here
GetBuffer(rx, 2, timeout); //again, substitute your serial port code here
Int temp = rx[1] | (rx[0] << 8);//convert returned data
float actual_voltage = temp/1024.0*5.0);
M
Setup S1/AN2/GP2 for digital and read state - return 1 byte
N
Setup S2/AN0/GP0 for digital and read state - return 1 byte
O
Setup S3/AN3/GP4 for digital and read state - return 1 byte
J
Setup S1/AN2/GP2 for digital, and set high
K
Setup S2/AN0/GP0 for digital, and set high
L
Setup S3/AN3/GP4 for digital, and set high
G
Setup S1/AN2/GP2 for digital, and set low
H
Setup S2/AN0/GP0 for digital, and set low
I
Setup S3/AN3/GP4 for digital, and set low
APPLICATION
The DLP-TEMP-G can be used to monitor temperature at the board or at a distance from the
board. The board supports monitoring of two temperatures. If more than two temperature
measure-ments are required, then the DLP-TEMP9 can be used to monitor/measure up to nine
temperatures.
The board comes with one sensor that is not soldered to the board so that the user has the option
of locating the sensor at a distance from the board using Category 5 cable. This design has been
successfully tested with both sensors located 200 feet away from the board using Category 5
cable. Two pairs of wires in the Category 5 cable are required for the connection. One pair is for
power and ground, and the other pair is for data and ground. If using both sensors, you can
either connect them to the board using one cable for both sensors since the cable has 4 pairs, or
2 cables if the sensors are to be placed in different locations.
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DISCLAIMER
Neither the whole nor any part of the information contained within or the product described in this
datasheet may be adapted or reproduced in any material or electronic form without the prior
written consent of the copyright holder.
This product and its documentation are supplied on an as-is basis, and no warranty as to their
suitability for any particular purpose is either made or implied. DLP Design will not accept any
claim for damages whatsoever arising as a result of use or failure of this product. Your statutory
rights are not affected.
This product or any variant of it is not intended for use in any medical appliance, device, or
system in which the failure of the product might reasonably be expected to result in personal
injury.
This document provides preliminary information that may be subject to change without notice.
CONTACT INFORMATION
DLP Design, Inc.
1605 Roma Ln.
Allen, TX 75013
Phone: 469-964-8027
Fax:
415-901-4859
Email: support@dlpdesign.com
Internet: http://www.dlpdesign.com
4
C1
.01
5
1
4
USBVCC
C2
10/10 Tant
PWREN#
SWVCC
C3
47pF
3
USBVCC
Q1
IRLML6402CT P
R10
360
C5
47pF
RXD
TXD
1
8
20
16
15
8
19
24
27
28
17
2
CBUS0
CBUS1
CBUS2
CBUS3
CBUS4
TXD
RXD
RTS#
CTS#
DTR#
DSR#
DCD#
RI#
23
22
13
14
12
1
5
3
11
2
9
10
6
DLP-TEMP
Version 2.1
U2
SWVCC
VCC5 IN
USBDM
USBDP
Vpp
Clock
Vcc
Gnd
Data
VCCIN/NC
RESET#
AVCC/NC
OSCI
OSCO
3V3OUT
FT232R
SWVCC
.1uF
C7
.1
C10
JP2
1
2
3
4
5
PROGRAMMING HEADER
2
4
2
FB1
240-1018-1
USB Type A Male Connector
R11
1.5K
U4
PIC12F683
VCC
GND
TXD
RXD
SWVCC
3
VCCIO
AGND
GND
GND
GND
TEST
25
7
18
21
26
CN1
1
2
3
4
C6
.47uF
3
2
1
2
3
OSC1
OSC2
R7
1.5K
4
R9
1.5K
GP3/Vpp
SWVCC
JP4
DS18B20 / TO92
Sensor 3
12MHz
3
2
1
3
2
1
SWVCC
JP1
DS18B20 / TO92
Sensor 1
JP3
DS18B20 / TO92
Sensor 2
4
6
D
C
B
A
5
GP0/PGD
7
GP1/PGC
GP2
5
R5
360
1
TXD (From host ->)
RXD (To host <-)
12MHz
PWREN#
SWVCC
1
D1
LED
D
C
B
A