TI MSP430 LaunchPad Temperature Demo Application


When you receive a new Texas Instruments MSP430 LaunchPad, it comes with a small demo application installed so you can easily check its functionality. The interesting thing is that it also interfaces with the PC through a virtual serial interface, but reading the data from a Linux PC appears to be non-trivial. This is partially caused by the fact that the user’s guide states that the demo application can be read with any serial console application, which in practice just doesn’t always work.

Attaching the LaunchPad

When an MSP430 LaunchPad is attached to the system, dmesg logs a few lines similar like these:

[19:52:40] usb 2-2.3: new full-speed USB device number 85 using ehci_hcd
[19:52:40] usb 2-2.3: New USB device found, idVendor=0451, idProduct=f432
[19:52:40] usb 2-2.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[19:52:40] usb 2-2.3: Product: Texas Instruments MSP-FET430UIF
[19:52:40] usb 2-2.3: Manufacturer: Texas Instruments
[19:52:40] usb 2-2.3: SerialNumber: 36FF49ABB1D22050
[19:52:40] cdc_acm 2-2.3:1.0: This device cannot do calls on its own. It is not a modem.
[19:52:40] cdc_acm 2-2.3:1.0: No union descriptor, testing for castrated device
[19:52:40] cdc_acm 2-2.3:1.0: ttyACM0: USB ACM device
[19:52:50] hid-generic 0003:0451:F432.003E: usb_submit_urb(ctrl) failed: -1
[19:52:50] hid-generic 0003:0451:F432.003E: timeout initializing reports
[19:52:50] hid-generic 0003:0451:F432.003E: hiddev0,hidraw3: USB HID v1.01 Device [Texas Instruments Texas Instruments MSP-FET430UIF] on usb-0000:00:1d.7-2.3/input1

According to line 9 of this logging, in this case the LaunchPad is attached to the system as ‘/dev/ttyACM0′.

Reading the data from MSP430 LaunchPad

For me only minicom (2400 8N1) was showing some data, but in contrast to what I understood from the user’s guide the received data is binary, not in ASCII.  I wrote a quick and dirty Perl script that easily allows for reading the data.

After attaching the LaunchPad and pressing button P1.3 on it, it starts to send data several times per second. Running the script below from the command line, outputs the current temperature.

Receiving serial data ...
22.2C 22.2C 22.8C 22.8C 22.8C 22.2C 22.8C 22.8C
22.2C 22.8C 22.8C 22.8C 22.2C 22.8C 22.8C 22.8C
22.8C 22.8C 22.8C 22.8C 22.8C 22.2C 22.2C 22.8C

The script is no rocket science, its main goal is to prove the LaunchPad is working properly and to act as a starting point for others.


use warnings;
use strict;

use Device::SerialPort;
use Time::HiRes qw( usleep );

my $PortName = '/dev/ttyACM0';
my $PortObj;
$| = 1;

print STDERR "Waiting for serial port ...\n";
while ( not( $PortObj = new Device::SerialPort ($PortName, 'false' ) ) ) {
print STDERR "Waiting: Cannot open serial port: $!\n";
sleep( 1 );

$PortObj->databits( 8 );
$PortObj->baudrate( 2400 );
$PortObj->parity( "none" );
$PortObj->stopbits( 1 );
$PortObj->handshake( "none" );

print STDERR "Receiving serial data ...\n";
my $newline = 8;
while ( 1 ) {
if ( not $newline ) {
# print 8 values per line
print "\n";
$newline = 8;
# try to read a byte of data
my ( $count, $data ) = $PortObj->read( 1 );
if ( ( defined( $count ) ) and ( $count != 0 ) ) {
# if data available, then convert from Fahrenheit to Celcius
printf( "%3.1fC " , ( ( ord( $data ) - 32 ) * 5 / 9 ) );
usleep( 100000 ); # wait 100ms

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