I have a board with a STM8S0003F3P6 MCU with its own 5V supply and a few other power supplies. What is the safest way to connect STM8S discovery SWIM programmer?
protect 5V
The SWIM pin 1 USB 5V and board 5V could be at different voltage levels. I don't want the USB port to power the board, so I disconnected them.
Protect SWIM signals when board is unpowered
There are 220 and 47 ohm resistors on the STM8S discovery. Is that sufficient to comply with slight power supply mismatch?
I am putting a 74HC4066 quad switch to ensure that the SWIM signals don't enter my board when my board is unpowered. The 74HC4066 has two ideal diode circuits to get powered by either supply. Is that good enough?
https://www.st.com/en/evaluation-tools/stm8s-discovery.html
https://www.st.com/resource/en/schematic_pack/stm8s-discovery_sch.zip
