custom board Esp32 + ch340c - not detected by PC - Page 1
Forum section: electronics / beginners

author: Cvijo
author_rank: Contributor
timestamp: April 10, 2025, 10:31:41 pm
content: Hi allI am a beginner in this, so I would like to ask for help if possible.This is my first custom board and PCB layout (second revision), and I am having trouble getting my CH340C(datasheet)to work. When connected to USB, I have 5V on the VCC pin on the CH340C, V3 pin is pulled to the ground with 100nF capacitor. I have attached the circuit board and part of the PCB layout.I can't figure out what is wrong and why my PC won't recognize a chip. When i plug in other boards that contain the same CH340C, the PC does detect it (so I would say it is not the driver).Any help would be appreciated.

author: xvr
author_rank: Frequent Contributor
timestamp: April 11, 2025, 11:39:31 am
content: You will have 5V on all output pins of CH340. But ESP32 is not 5V tolerantSo it will effectively short all outputs of CH340 to 3.3V rail via internal diodes.Yoy have to switch CH340 to 3.3V rails. Disconnect VCC from 5V, join it with V34 and connect to 3.3V power rail.

author: Cvijo
author_rank: Contributor
timestamp: April 11, 2025, 12:25:41 pm
content: Thank you for reply, i am aware of that and after searching a lot before, it is safe to use 5V on ESP32 since it is only 3mA there is even some official documentation on that, but now i can't find it. And I have tested all other boards I have that use CH340C and they used 5V and grounded V3 pin, so that is not the problem why my PC won't detect it, and I tried 3V too before I posted here.

author: xvr
author_rank: Frequent Contributor
timestamp: April 11, 2025, 12:33:28 pm
content: QuoteIt will be safe if you add series resistors between output of CH340 and input of ESP32, to limit current through input protection diodes of ESP32 to allowable level. Without resistors this current will be determined by current capablity of CH340 outputs which will work in short circut mode (that definitely not good for them)

author: CaptDon
author_rank: Super Contributor
timestamp: April 11, 2025, 12:41:12 pm
content: Read as much online info as you can about the CH340 family of problems. As I recall, one of the releases of Windows with a particular USB driver installed would 'brick' a CH340 by erasing or altering the internal EEPROM content. Maybe yours got bricked. There is a way to revive the device. Look for the 'restoring CH340 back to life' thread or something similar. My 'NANO' has the CH340/CH341 and is wasn't recognized. I had to install the actual driver downloaded from a chinese website, and yes that is a scary thing to do. Fortunately that is on an old XP laptop that never goes on the internet.

author: Cvijo
author_rank: Contributor
timestamp: April 11, 2025, 04:33:57 pm
content: Quote from: xvr on April 11, 2025, 12:33:28 pmYou mean on TX and RX lines, or Enable and CHIP_PU pins ? .. i added 0 ohm resistors on TX and RX lines so i can put some series resistor on it but don't know what size.

author: Cvijo
author_rank: Contributor
timestamp: April 11, 2025, 04:36:57 pm
content: Quote from: CaptDon on April 11, 2025, 12:41:12 pmThank you .. that did the trick.. now its working and if anyone else got into the same problem here is thelinkfor WCH manufacturer