Using C with the TI EZ430-RF2500 dev chips - c

Question

So what I am trying to do is receive a packet and print the payload to the serial port. Listening at the port is a python script that reassembles the payload and does some things with it.
Here is the code:
#include "mrfi.h"
int main(void)
{
BSP_Init();
MRFI_Init();
//Initialize the serial port
P3SEL |= 0x30;
UCA0CTL1 = UCSSEL_2;
UCA0BR0 = 0x41;
UCA0BR1 = 0x3;
UCA0MCTL = UCBRS_2;
UCA0CTL1 &= ~UCSWRST;
MRFI_WakeUp();
MRFI_RxOn();
__bis_SR_register(GIE+LPM4_bits);
}
//This is run when a packet is received
void MRFI_RxCompleteISR()
{
uint8_t i;
P1OUT ^= 0x02;
mrfiPacket_t packet;
MRFI_Receive(&packet);
char output[] = {" "};
for (i=9;i<29;i++) {
output[i-9]='a';
if (packet.frame[i]=='\r') {
output[i-9]='\n';
output[i-8]='\r';
}
}
TXString(output, (sizeof output));
}
I send a packet with test data but nothing. Anybody have any insights? Also while just so you know I am learning C while I do this, so any pointers on design would also be awesome.
Thanks.

Answer 1

I don't know why your code isn't working, but here are some design hints as requested.
Since this appears to be a hostless system, main() should most likely return void. I assume that you didn't post all of your code, as in a hostless there should also be an eternal loop in main().
Remove all "magic numbers" from the code and replace them with #defined bitmasks or constants.
Reduce all code inside interrupts to a minimum. The optimal interrupt only sets some flags.
Don't use unspecified width (output[]) for arrays/strings. Embedded system design is about making things deterministic and fixed.
Here is an example of another way to write that loop. As I have no idea what this program is supposed to do, replace the constant names with something that makes sense.
uint8_t output[OUTPUT_N];
memset(output, ' ', SPACES_N);
output[OUTPUT_N - 1] = '\0';
for(i=0; i < SOMETHING; i++)
{
output[i + A_OFFSET] = 'a';
if(packet.frame[i + FRAME_OFFSET] == '\r')
{
output[i + CR_OFFSET] = '\r';
output[i + LF_OFFSET] = '\n';
}
}