Olimex Support Forum

Microcontrollers => ESP8266 => Topic started by: Toxalbumine on April 27, 2016, 12:21:10 pm

Title: ESP8266-EVB UART problem
Post by: Toxalbumine on April 27, 2016, 12:21:10 pm
Hi,

I have some troubles getting the UART working. When the board is booting I get the "ready" message, so I guess my wiring is good (at least the RX), but the problem is that I cannot transmit anything (but I can a LED blinking on the board when I type something) and I constantly receive shitty characters..

I have tried many different terminals like minicom, cutecom, arduino IDE, ESPlorer, cu and the result is the same.
I have set the speed at 115200 (and others) and of course 8-N-1, I have plugged the green cable (RX) on the pin 3 (TX), the red (TX) on the pin 4 (RX) and the blue one (GND) on pin 2 (GND).

PS : I have the ESP8266-EVB and the USB-Serial-Cable-F and I have debian Jessie

Thanks in advance.
Title: Re: ESP8266-EVB UART problem
Post by: LubOlimex on April 27, 2016, 12:59:36 pm
Hey,

Look at the bottom of the product page at the FAQ section. It says:

"
I want to send basic AT commands to the board but I receive no response. The strange thing is that I receive "ready" when I power the module. What is the problem?

All AT commands must end with carriage return and line feed - "/r/n". Your terminal software might have such a new line option - transmitting CR+LF at the end of each command. If it doesn't - either use another terminal software or try to send the commands with "CTRL"+"J" keyboard combination, instead of "ENTER".
"

Also test with 57600 baud.

Best regards,
Lub/OLIMEX
Title: Re: ESP8266-EVB UART problem
Post by: Toxalbumine on April 27, 2016, 09:22:49 pm
Thanks for your answer.

Yes I have read carefully the FAQ and all the other documentations and I put both CR & LF at the end of each command. The problem is that a receive constantly the NUL character (0x00) regardless the speed (I have tried all the possibility..), could it be my Usb - serial adapter ?
Title: Re: ESP8266-EVB UART problem
Post by: LubOlimex on April 28, 2016, 11:32:10 am
It can be. Did you try to swap RX and TX just in case?

Is the cable installed properly under your OS? Can you test it with other serial device?

As usually avoid long USB cables and USB hubs that might affect the data signals.

Best regards,
Lub/OLIMEX
Title: Re: ESP8266-EVB UART problem
Post by: JohnS on April 28, 2016, 11:59:35 am
Are you just using upper case?

115200 8N1 should work, at least for boards I've used.

It's vital to be 100% accurate in typing a command and as stated you normally need CR and then LF (and/or appropriate settings for the terminal program).

CR is Ctrl M
LF is Ctrl J

John
Title: Re: ESP8266-EVB UART problem
Post by: Toxalbumine on April 28, 2016, 01:28:37 pm
Yep I have already tried it.
Properly installed ? I think yes, I am under debian, I can see the module "pl2303" that is loaded and can see the /dev/ttyUSB0 + dmesg seems ok and my user is in the group "dialout" so there are no permission problem.

I measured the voltage of the cable and I barely have 0.250 V on the usb port at the back of my computer and 0.125 V at the front, I am far from the 3.3 V !! I don't know if I have the good technique to measure it, I only have a multimeter, I don't have an oscilloscope to measure the ttl signal..

When I use the back USB ports, it's better I can see the TX led blinking and I get "ERROR" message when I type anything, something that I don't have with the front usb port.

I am thinking about getting a good FTDI cable..
Title: Re: ESP8266-EVB UART problem
Post by: JohnS on April 29, 2016, 12:25:37 pm
PL2303 work fine.

But - you should not have that sort of voltage drop.

Can you not power the EVB from some other place - a USB hub maybe?

John
Title: Re: ESP8266-EVB UART problem
Post by: Toxalbumine on April 30, 2016, 11:06:14 am

I only tested the cable : I directly wired the TX on the RX then I measured the voltage and it was the same.
I will test with another cable.. to be continued..
Title: Re: ESP8266-EVB UART problem
Post by: Toxalbumine on May 06, 2016, 12:07:34 pm
Good news guys !

I just receive my new USB -> UART adapter and.... it works !!! :-)

I think the one I receive from OLIMEX was faulty..