In this document, I will explain how to use the CH341A device and how to modify UEFI, based on my nearly four months of experience. While working with the CH341A I encountered many issues some which I solved by reading docs applying engineering skills and sometimes just by luck. Since there are so many confusing solutions exists I've decided to collect them all into one document. In this document i will tell all informations i know.
This is a cheap programming device (Chinese origin) usually contains an integrated circuit labeled CH341A. And you can program, 25XX/24XX EEPROM series.
The most widespread misconception about this device on the internet is that it uses a voltage higher than 3.3V while programming the SPI chip. You can find hundreds of texts or videos on the internet claiming that the device is poorly manufactured and tends to burn chips by using too much voltage. These people argue that the CH341A works unreliably and therefore needs to be modified (by connecting pin 15 of the chip to the regulator’s input, and pin 9 to the output to achieve a 3.3V output on the SPI lines). However, the device works perfectly fine in its original state. If you have doubts you can check out this video [x] for proof. Do not fall for the wrong information generated by these people who are unaware of Ohm’s law, and do not attempt to modify your device. Doing this modification can make your programmer unstable, leading to disconnections during read or write operations, or even unstable voltage when the clip is directly in contact with the chip. Other important point I want to tell is that a modified version of this cheap device has been released to the market with the CH341B chip. I own both devices, and I will share their pictures below:
From these two photos, you can easily recognize which one is the original device. The one you see on the right is a modified version of the real device you can already tell from the poor quality English written on it. This modified device is essentially marketed as a “fix” for the so called voltage issue I just mentioned. However, this so-called fix introduces instability in the voltage output, which causes frequent disconnection problems with many SPI chips. Unfortunately, this modified device is very commonly sold in the market, and in my country, it was really difficult for me to find the genuine one. I definitely do not recommend buying this modified version; as I said, it works terribly. If the device you bought thinking it was original looks like the one shown in the photo, then unfortunately, due to this fake product defect, it will be very difficult for you to carry out programming. The most common problem users face is that when the clip connected to the device makes contact with the chip, the CH341A disconnects from the computer. However, this disconnection problem can be reduced with some tricks. For example, when I connected a 570 µF capacitor between VCC and GND, I was able to read some chips successfully but I repeat, only some!
When I used the original device, the chip connection worked flawlessly. The computer recognized the device without ever experiencing disconnection issues. Moreover, the program successfully identified the chip. However, whenever I attempted to read or write, some random bits inside the chip (usually about 35% of the chip) were read incorrectly. This is another common problem. The issue arises because the 3.3V regulator output inside the CH341A device is too noisy. Since the device is extremely cheap, a lot of low-quality components were used in its design. The solution I followed was to connect a 0.1 nF ceramic capacitor between the VCC and GND terminals of the device. This way, all bits were successfully read and written correctly.