STM8 SWIM Debug Protocol
Hello,
I’ve been working on implementing a SWIM master using an STM8 device to interface with a STM8S105K6 target. This is part of a tester software project that was previously using the ST7 debug protocol and is now being ported to the STM8.
I’ve followed the entry sequence described in UM0470, and I believe the waveforms match what's expected. Attached below is a screenshot from the oscilloscope:
Yellow trace = RESET pin
Green trace = SWIM pin
As you can see:
A long low pulse initiates the SWIM entry sequence.
Followed by 4 x 1kHz pulses and 4 x 2kHz pulses.
Then I set the SWIM line high and switch it to input mode to await the slave response (Step 4 per UM0470).
However, no response is received from the target. The line stays high and never toggles.
Below is the relevant code section (i use raisonance ride7 dev environment):
unsigned char swim_entry(void){
unsigned long a;
unsigned char m = 1;
char buf[1];
swim_config(0);
ADC_disable;
RES(1);
SWIM(1);
delay_ms(10);
RES(0);
delay_ms(10);
SWIM(0);
delay(1000);
//delay (30); // 16us+ delay to get into SWIM mode
// start 1khz sequence:
for(a = 0; a < 4; a++){
SWIM(1);
delay(FIRST_PULSE);
SWIM(0);
delay(FIRST_PULSE);
}
// start 2khz sequence:
for(a = 0; a < 4; a++){
SWIM(1);
delay(SECOND_PULSE);
SWIM(0);
delay(SECOND_PULSE);
}
SWIM(1);
swim_config(1); // swim as input mode
for (a=0; a<10000; a++)
{
delay(125);
if (!IN_SWIM)
{
m = 0;
}
if (m == 0 && IN_SWIM)
{
m = 2;
break;
}
}
if(m != 2){
RES(1);
return FALSE;
}
swim_config(0);
SWIM(1);
delay(100);
// write 0x0A0 to the SWIM_CSR
buf[0] &= 0b000;
buf[0] |= SWIM_BITMASK;
if(!swim_write(3, 0, 0x7F, 0x90, buf)) {
RES(1);
return FALSE;
}
// End
SWIM(1);
RES(1);
delay_ms(20);
return TRUE;
}
Any ideas of what could be happening?
I appreciate any insight from others who’ve implemented custom SWIM masters, especially from STM8 to STM8 communication.
Thanks in advance!