Uh uh uh, after several versions, CH340T still doesn't respond

zqdl8

Uh uh uh, after several versions, CH340T still doesn't respond [Copy link]

 

Please help me, is there any problem with this picture? After soldering, it doesn't work when connected to the computer horizontally or vertically.

dcexpert

Pin 19 is connected to USB's 5V, not 3.3V.

If there is no special requirement, it is better to use CH340C, which has a built-in 12M crystal. Or use CH330N, SO-package, which has fewer pins and is easy to route.

chunyang

As mentioned above, the power connection is incorrect. When connected to the USB port of the PC, the power should be obtained from the USB, otherwise the device will not be enumerated and the PC will certainly not recognize it. The connection method for 3V power supply is for the USB host of the MCU, which is different from the PC.

LuJianchang

The VCC of CH340 can be used without sharing the 5V of the computer USB interface, but it must be grounded. CH340T uses 3.3V power supply, and pin 5 must be connected to VCC. If it cannot be recognized, is it because you have not installed the driver?

zqdl8

LuJianchang posted on 2020-4-14 08:57 The VCC of CH340 can be used without sharing the 5V of the computer USB interface, but it must be shared with the ground. CH340T uses 3.3V power supply, and pin 5 must be connected to VCC. Cannot identify whether it is...

When I plugged it into the computer, the computer didn't even respond when it found the device, let alone the driver recognition and installation.

I connected pin 5 to 3.3V

LuJianchang

zqdl8 posted on 2020-4-14 10:43 Plug it into the computer, the computer doesn't even respond when it finds the device, let alone the driver recognition and installation. Miraculously, I connected 3.3V to pin 5

Check whether D+ and D- are connected inversely, and whether the chip and peripheral devices are soldered properly.

EricCheng

The TX and RX of the MCU are also connected in reverse

zqdl8

EricCheng posted on 2020-4-14 13:54 The TX and RX of the MCU are also connected in reverse

I haven't soldered the MCU chip yet, I just soldered the CH340T and its peripheral components. The MCU wiring TX and RX are connected to RX and TX respectively.

zqdl8

I checked with an oscilloscope and found that the 12M crystal oscillator was not vibrating. I tried the two capacitors 22P 33P 20P. It's weird.

zqdl8

Please also post the PCB here so that I can have a look.

zqdl8

Doesn’t anyone know?