Serial USB TTL Communication Problems (Newbe Question)

Use this forum to chat about hardware specific topics for the ESP8266 (peripherals, memory, clocks, JTAG, programming)
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Re: Serial USB TTL Communication Problems (Newbe Question)

By gerardwr
- Tue Dec 09, 2014 12:39 pm #4399
haroldjclements wrote:I am have tried with both a CP2102 USB to UART TTL
Harold Clements


It's getting more and more difficult to give some sensible advice, considering al the tests you have done.

This is my last shot:
- use the CP2102 and "jiggle" the serial input line on and off to the 3.3V
- some weird characters should appear in your serial terminal. If you see NO weird chars then set the baud rate to a low rate, like 300 or 1200. You MUST see weird characters in the terminal!

Testing that the ESP does output on the TX line can be done by using an oscilloscope, but not many us have access to one. You COULD connect an LED with a serial resistor to the TX line to be absolutely sure that the signal to the Blue LED also reaches the TX connector pin.

That's about all the inspiration I can give you.
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Re: Serial USB TTL Communication Problems (Newbe Question)

By x5442
- Tue Dec 09, 2014 2:52 pm #4413
haroldjclements wrote:I am have tried with both a CP2102 USB to UART TTL and an Arduino Uno

Can you verify the voltage on RX/TX lines? There could be problem with both above running at 5 volts, while ESP8266 outputs only 3.3V (the cheaper CP2102 variant CP2109 requires input voltage 0.7*VDD, but because it is USB powered, VDD is 5V and 0.7*5 = 3.6, which is higher than 3.3V).
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Re: Serial USB TTL Communication Problems (Newbe Question)

By haroldjclements
- Tue Dec 09, 2014 3:26 pm #4419 x5442,
I have measured RX and TX lines are both running at just under 3.3v (3.18v).

garardwr,
I am not 100% sure that I understand. Are you saying to repeatable short the 3.3v on the TTL with the RX pin (on the TTL) (I also tried the TX pin) and see if I get gibberish in my terminal? If so, no, I don't get anything on the terminal screen. However, I did link up the RX/TX of the CP2102 (COM3) with the TX/RX of the Arduino (COM4) and I could send messages back and fourth.

martinayotte
I did have the GND's connected, but since I have but the 10K resistor across the RST and GPIO0 pins, I did (accidentally) neglect it. I will try with the GND's connected...

Thank you once more. I understand if you guys cannot help anyone. I will get another ESP and see if that is any better...
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