Hi. Could someone please confirm if upon connecting to a USB power supply there should be immediately any voltage at all on MOSI or MISO?
One of the videos linked above seems to indicate that we can check for the possible need for the mod by confirming that there is 5V on the data pins. When I plug my CH341A adapter (black version as discussed here) into a USB power supply I am seeing 5V on CLK, CS pins but I am not seeing any voltage at all on MOSI or MIOS (neither 5v or 3.3v). It is in SPI programming mode (with the jumper bridging 1-2).
Simply put. There is a need to do the modifications!! Unless, if you are going to use the programmer only on your own hardware and it works for you. If you try it on other hardware e.g. motherboards, without doing your proper research first, then it could lead to a damaged equipment, Ditto. So all depends what you want to do with the CH341A. If it works "as is" for you, then fine if used on your own known equipment. If you are going to use it on other unknown hardware circuits containing low voltages components then be aware of the risks.
I measured again as per request and confirm the measurements are as per the videos. See picture below.
In the meantime I bought and received an additional CH341A which will be modified with adding a 3.3v/5V voltage switch. The original recovered CH341A will be used in project as daughter-board and/or its components transferred to a new design PCB with additional mods i.e.
1 Add a switch to be able to choose between required voltage sources as either 3.3V, 2.8V, 5v or target board supply.
2 Breakout all pins to be available for use in other modes as per datasheet (i.e. Development board).
3 Add specific standard headers.
4 etc.
CH341A
![CH341A Serial Memory Programmer Power Supply Fix](https://www.eevblog.com/forum/index.php?action=dlattach;topic=96820.0;attach=1024066;image)