ESP8266 Community Forum

- Fri Aug 10, 2018 5:24 pm #77682 Hello,

I'm just getting started with ESP8266 (using ESP-WROOM-02 module) and have connected it to a Teensy LC which I am using as a serial passthrough.

I was able to flash the ESP8266 with the latest AT firmware using the Espressif flash download tool (again, using the Teensy LC as a serial bridge), and I verified the flash was successful by dumping the flash and comparing the checksum against the uploaded file. Flashing was done at 115200bps.

However, on boot (GPIO15 low, GPIO0 high, EN high), I get gibberish when sending and trying to receive data over the serial lines. I have tried about every baud rate I can think of (9600, 19200, 38400, 57600, 74880 which I found in the docs (and gets me the boot loader output clearly), 76800, 115200) and have had no luck, except that on some I seem to get more gibberish than others

The Teensy LC does not support flow control and only has support for RTS (not CTS); I wonder if that is the issue, as everything I'm reading seems to indicate that the default bitrate in the firmware should be 115200?

Is there a way I can set the bitrate through the flashing process (which I know works)? Or do I need to find a USB-TTL cable with flow control to be able to crack this thing and set the bit rates?

Thanks!

- Sun Aug 12, 2018 5:40 am #77700 Normally, by default the modules will start up with their serial interface outputting start up messages at 74880 but then detect their crystal frequency and re-adjust so that further communication is at 115200.

If you have the Teensy set to 115200 it will therefore see some initial 'garbage' but then further communications at 115200 should be OK.

Depending on your overall application it might also be worth considering moving application code over entirely from the Teensy to the ESP8266 module and do everything on one module. The ESP8266 is quite powerful and has a good amount of firmware and RAM space. Doing this and avoiding tying two MCU s together via serial is much simpler and will most of the time give overall better performance.

- Sun Aug 12, 2018 7:33 am #77701 Hey, thanks for your response. In the time I was stuck in moderation limbo, I found the issue.

As with so many other issues I read about... it was power delivery. The gibberish I was seeing was the ESP repeatedly restarting after I had switched from 74880 to X baud rate. One of the pins in my breadboard was not making a secure connection. I suppose those wear out over time like everything else .

As far as your other recommendation -- my project uses a ton of analog inputs so it doesn't make sense for me to switch to something else. I can handle the inter-module communication as long as the ESP actually does its thing!

Thanks!