Electronics > Repair
CH341A Serial Memory Programmer Power Supply Fix
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fudmuffin:
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).

pupa:

--- Quote from: fudmuffin on July 15, 2020, 03:52:16 am ---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).

--- End quote ---

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   


pupa:

--- Quote from: jakeisprobably on July 14, 2020, 06:27:21 am ---I reworked the attached images above. I also uploaded a new version of the schematic in PDF on github. The dot pro files are included for kicad. I haven't bothered to make it pretty on github. The files are a bit of a mess as these are the result of creating the files on one computer and transferring them to another, doing a couple more edits, then making the git repository. On the bright side, I can confirm, all the files and libraries needed are included. I have also created a 1:1 reproduction of the programmer in PCBnew. Have fun.   
https://github.com/Upcycle-Electronics/CH341A-Pro

--- End quote ---
As per original circuit design?
Any mods as per requirement for voltages and stability?
fudmuffin:

--- Quote from: pupa on July 15, 2020, 05:27:24 pm ---I measured again as per request and confirm the measurements are as per the videos. See picture below.

--- End quote ---

Thank you for your confirmation which leads me to conclude that my CH341A chip must be damaged, as I am seeing 0v on MOSI and MIOS when the adapter is plugged into USB power (strange, as the device still enumerates correctly on USB when plugged into a computer). Anyway I have a new one on the way so I can do comparisons when it arrives. Thanks so much for your work.
pupa:

--- Quote from: fudmuffin on July 15, 2020, 11:50:13 pm ---
--- Quote from: pupa on July 15, 2020, 05:27:24 pm ---I measured again as per request and confirm the measurements are as per the videos. See picture below.

--- End quote ---

Thank you for your confirmation which leads me to conclude that my CH341A chip must be damaged, as I am seeing 0v on MOSI and MIOS when the adapter is plugged into USB power (strange, as the device still enumerates correctly on USB when plugged into a computer). Anyway I have a new one on the way so I can do comparisons when it arrives. Thanks so much for your work.

--- End quote ---
No hassle at all.
Can it read/write/verify successfully? Some units have errors on PCB. The quality systems from China are difficult to control and maintain. So you should check your unit thoroughly for solder bridges or missing components.
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