ESP32 Forum

Hi all,

I'm trying to flash my ESP32 but I have that kind of error which seems more or less common :
I tried all the suggestions in the different topics : change the USB cable, put the GPIO0 pin to a GND while connecting,change the USB port,...

The weird thing is that I can flash using the command in the esp/openocd-esp32 file:
As you can see I'm using the olimex-arm-usb-ocd-h with JTAG. How could you explain I can flash using that command but I can't using make flash ?

I would like to use eclipse and see the output of my esp using the make monitor command to see for example wifi scan. But it is the same error when I want to flash from eclipse. The only way I found to see my wifi scan is using the debug mode in eclipse and seeing the values in the variables.

Do you have any ideas how I could see my results and the print messages I used in my code ? When I'm using make monitor I only have the lines in the attach file.

I'm using :
Eclipse IDE for C/C++ Developers

Version: 2018-12 (4.10.0)

Thank you for your help

Which development board are you using? Based on lack of monitor output, it seems that /dev/ttyUSB0 is not connected to the UART of ESP32. If you see multiple /dev/ttyUSBx ports in your system, you might try other ports and see if one of them works.

I'm using the ESP-WROOM 32 without a development board, just the ESP32 module connected with JTAG to the olimex arm usb ocd h.

It seems that I only have ttyUSB0 in my dev file. Else it's only ttyXX ot ttySXX

Hi salomonreinach,

salomonreinach wrote: ↑

Wed Feb 06, 2019 1:05 pm

As you can see I'm using the olimex-arm-usb-ocd-h with JTAG. How could you explain I can flash using that command but I can't using make flash ?

With "make flash" you are using serial pins U0TXD (GPIO1) / U0RXD (GPIO3) for program upload and GPIO0 to put the ESP32 into download mode. You should see "waiting for download" message on the monitor if you select correct USB port, pull GPIO0 down and this interface works correctly, see also viewtopic.php?f=12&t=9103&p=38027#p38024

On the other hand with JTAG you send the program using JTAG interface pins GPIO12, GPIO13, GPIO14, GPIO15 and EN.

And when I'm running it's the ttyUSB0 that appear and disappear when I plugged and unplugged my esp32.

I believe the single ttyUSB0 you see is associated with olimex-arm-usb-ocd-h and works for the JTAG interface only. To flash with "make flash" you need a separate USB-to-serial interface dongle connected to the UART pins I mentioned above.

Ok thank you for your answer, I also can't use the make monitor command with JTAG but with a serial interface using TXd and RXD pin ?
Or is there an other solution to see my messages in the code I send to the ESP32 elsewhere than in the debug mode ?

The command "make monitor" works over the serial interface. You need an extra USB dongle connected to TXD and RXD pins.

To avoid multiple wires and two additional physical devices (one for JTAG debugging and one for serial logs) please consider https://docs.espressif.com/projects/esp ... r-kit-v4-1

How it works is described in https://docs.espressif.com/projects/esp ... w-it-works

Thank you very much for your answers