I began experimenting last night with the SPI module of the MSP430 mcu's on the launchpad. The experiment involved connecting two launchpad's together with a full-duplex SPI interface. One launchpad was configured as a master and the other as a slave. Full duplex communicationg between the two boards exists allowing both the master and the slave to send data simultaneously. When the switch on on either board is pressed the value on the io port is transmitted to the other device causing the led to light up. I soldered the male headers that came with the Launchpad board on to two of the kits so that I could get easy access to the processor pins. SPI is serial peripheral interface. You can find more about
SPI at wikipedia. This is relatively easy to set up and play with. Nothing but four wires between the launchpads was required. The wiring schematic is shown below along with the code for the master and slave. The source code came from the TI code samples that were downloaded from their website. A couple of minor adjustments had to be made for the launch pad hardware to work primarily to use the push-button switch that is connected on P1.3. No pull up resisters were used in the experiment.
Though this is a simple experiment it provided an opportunity to learn how to use the Code Composer Studio tool to program the launchpads. Additionally, it helped to learn more about how to use the MSP430 SPI module. This is the beginning step in developing code to allow a launch pad to communicate with a EZ430 wire less RF target board that will be piggybacked on the lauchpad for wireless capability.
//******************************************************************************
// MSP430G2xx2 Demo - SPI full-Duplex 3-wire Slave
//
// Description: SPI Master communicates full-duplex with SPI Slave using
// 3-wire mode. The level on P1.3 is TX'ed and RX'ed to P1.0.
// Master will pulse slave reset for synch start.
// ACLK = n/a, MCLK = SMCLK = Default DCO
//
// D. Dang
// Texas Instruments Inc.
// December 2010
// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10
//******************************************************************************
#include
void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
P1OUT = 0x08; // P1.3 set, else reset-Modification for LP
P1REN = 0x08; // P1.3 pullup- modified for LP
P1DIR = 0x01; // P1.0 output, else input
USICTL0 = USIPE7 + USIPE6 + USIPE5 + USIOE; // Port, SPI slave
USICTL1 = USIIE; // Counter interrupt, flag remains set
USICTL0 &= ~USISWRST; // USI released for operation
USISRL = P1IN; // init-load data
USICNT = 8; // init-load counter
_BIS_SR(LPM0_bits + GIE); // Enter LPM0 w/ interrupt
}
// USI interrupt service routine
#pragma vector=USI_VECTOR
__interrupt void universal_serial_interface(void)
{
if (0x08 & USISRL) // Modified for Launch Pad
P1OUT = 0x01;
else
P1OUT &= ~0x01;
USISRL = P1IN;
USICNT = 8; // re-load counter
}
//******************************************************************************
// MSP430G2x21/G2x31 Demo - SPI full-Duplex 3-wire Master
//
// Description: SPI Master communicates full-duplex with SPI Slave using
// 3-wire mode. The level on P1.4 is TX'ed and RX'ed to P1.0.
// Master will pulse slave reset for synch start.
// ACLK = n/a, MCLK = SMCLK = Default DCO
// D. Dang
// Texas Instruments Inc.
// October 2010
// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10
//******************************************************************************
#include
void main(void)
{
volatile unsigned int i;
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
P1OUT = 0x08; // P1.3 set, else reset - modified for LP
P1REN = 0x08; // P1.3 pullup - modified for LP
P1DIR = 0x01; // P1.0 output, else input
USICTL0 = USIPE7 + USIPE6 + USIPE5 + USIMST + USIOE; // Port, SPI master
USICTL1 = USIIE; // Counter interrupt, flag remains set
USICKCTL = USIDIV_4 + USISSEL_2; // /16 SMCLK
USICTL0 &= ~USISWRST; // USI released for operation
USISRL = P1IN; // init-load data
P1DIR = 0x08; // Reset Slave
P1DIR &= ~0x08;
for (i = 0xFFF; i > 0; i--); // Time for slave to ready
USICNT = 8; // init-load counter
_BIS_SR(LPM0_bits + GIE); // Enter LPM0 w/ interrupt
}
// USI interrupt service routine
#pragma vector=USI_VECTOR
__interrupt void universal_serial_interface(void)
{
if (0x08 & USISRL) // modified for Launch pad
P1OUT = 0x01;
else
P1OUT &= ~0x01;
USISRL = P1IN;
USICNT = 8; // re-load counter
}
I tried phillips and hex and square bits and then tried to drill the screws out. Even then the back would not come apart. I then tried to pry the shell apart, but found it was put together tightly and securely. As a result the outside shell was rendered useless by the time I got to the gyro. I feared that the circuitry would be damaged even though I was careful. In the end I managed to remove the gyro from the plastic case. Then 
I unsoldered the female pass-through port connector. This will allow me to make a cable with a female plug so that I can use the male connector that is attached to the gyro board. Later will begin experimenting with the hardware interface and making use of the data that the gyro provides. 
The Launch Pad development board provides unpopulated pads for adding a header so that a target board such as the 
connection outdoors for at least half a foot ball field distance. In my next post I hope to be able to share the results of experimenting with this setup to allow the two boards to talk to one another.