Posted on November 28, 2017 at 13:12Hello Sang hyeon Jeong,
Once SWIM pin is configured as output, it is no longer possible to establish SWIM communication with MCU.
Default state of SWIM pin is remained when STM8 device is in reset state. As a result it is still possible to use SWIM when MCU is in reset state by controling reset pin. Unfortuantely for STM8S001 you can't use this solution, because there is no reset pin.
In your case there is still a very short time when STM8S001 has active SWIM pin. This is during POR (Power On Reset) and also for a short while during code execution, until application reconfigures SWIM pin to output. But this time slot is very short. So the only solution, which teoretically could help here is a custom SWIM programmer, which would keep sending SWIM initial sentence to STM8S001 starting from the moment, when supply voltage is attached to MCU. This would probably allow MCU to receive a SWIM command in moment of time, when SWIM is active.
To avoid this problem in future I would propose using one of the two solutions listed below:
1. To add few seconds of delay as a first code executed by MCU. This is recommended by our documentation.
2. To implement simple UART communication in a way that after receiving specific pattern of UART data MCU will reconfigure SWIM pin back to its original configuration.
Regards
Szymon
