ESP8266 Community Forum

- Tue Jan 19, 2016 7:01 pm #39266 I have a ch340g USB serial adapter connected to the yellow test board (3xAA) via a 4 channel level converter.

I receive the boot message:

Ai-Thinker Technology Co.,Ltd
ready

But I can't transmit anything. The only way I can transmit is to connect a multimeter across tx and ground (or rx/ground on esp) then transmit, which works.

I have (usb/level converter)
RX->HV2
TX->HV1
VCC->HV
GND->GND

Then (level converter/esp test board)
LV1->TXD (it's actually RXD on the esp because the board is mislabelled)
LV2->RXD (txd)
GND->GND
LV->VCC

Does that all look OK?

- Wed Jan 20, 2016 5:33 am #39286 Why don't you just use a 3.3v FTDI?

- Wed Jan 20, 2016 12:40 pm #39303

Why don't you just use a 3.3v FTDI?

The only usb adapter I have is a ch340g. It has a 3v/5v switch but it only switches the vcc line, logic levels are always 5v!

- Wed Jan 20, 2016 12:59 pm #39306

I have a ch340g USB serial adapter connected to the yellow test board (3xAA) via a 4 channel level converter.

I receive the boot message:

Ai-Thinker Technology Co.,Ltd
ready

But I can't transmit anything. The only way I can transmit is to connect a multimeter across tx and ground (or rx/ground on esp) then transmit, which works.

I have (usb/level converter)
RX->HV2
TX->HV1
VCC->HV
GND->GND

Then (level converter/esp test board)
LV1->TXD (it's actually RXD on the esp because the board is mislabelled)
LV2->RXD (txd)
GND->GND
LV->VCC

Does that all look OK?

I have some experience with that yellow board. Not sure if this will help, but here are my thoughts:

1. Make sure we are talking about the same pin connections on the board. The pic illustrates how I would do it, depending upon where I was connecting.

2. Verify that your level shifter is working properly. Sometimes they are not what they seem (look at the comments for the one advertised here http://www.banggood.com/Two-Channel-IIC-I2C-Logic-Level-Converter-Bi-Directional-Module-p-970227.html

3. Dump the batteries and use a known good supply that outputs at least 500mA - since there is a 3.3V regulator on board, I use a 5V 1 amp supply for testing. When it is working, you can go back to the batteries.

You are close, so let us know what the problem was.

Cheers,
DrG