Developing Firmware for the ESP-WROOM-32 Module

This tutorial shows how to develop and debug a simple WiFi HTTP server for the ESP-WROOM-32 module using Visual Studio and VisualGDB. Before you begin, install VisualGDB 5.3 or later.

In order to debug the ESP-WROOM-32 module over JTAG, you will need to use an external stabilized 3.3V power supply and a JTAG debugger (e.g. Olimex ARM-USB-OCD-H) and connect it to certain pins of the ESP-WROOM-32 module. The table below shows the relevant pins:

ESP32 signal ESP-WROOM-32 signal JTAG signal JTAG20 pin
+3.3V 3V3 VCC 1
CHIP_PU EN SRST 3
GND GND GND 4
MTDI GPIO12 TDI 5
MTMS GPIO14 TMS 7
MTCK GPIO13 TCK 9
MTDO GPIO15 TDO 13

See ESP-WROOM-32 schematics for more details.

You can use a breadboard to easily connect the relevant signals to a JTAG cable as shown below:wroom

Warning! Be careful not to short-circuit nearby signals and double-check everything with a multimeter. Also note that confusing +3.3V and ground may instantly burn your ESP-WROOM-32!

The final setup of the ESP-WROOM-32 and a JTAG debugger would look as shown below:2boards

Once the wiring is configured, you can proceed with creating and testing out a basic project.

  1. Start Visual Studio and open the VisualGDB Embedded Project Wizard:01-newprj
  2. Proceed with the default “New Project->MSBuild” setting:02-msbuild
  3. Select the ESP32 toolchain and the regular ESP32 device:03-esp32
  4. As we have not soldered any LEDs on the board, we will proceed directly with the Wi-Fi example. Select “HTTP Server” and proceed with the default configuration:04-server
  5. Connect your JTAG debugger to USB and select it in the “Debug Using” field. VisualGDB should automatically detect supported JTAG programmers and install the necessary drivers:05-dbgconf
  6. Click “Test” to check the connection. If you see errors like “scan chain interrogation failed”, double-check your wiring and power:06-test
  7. Press “Finish” to create the project and build it via Ctrl-Shift-B:07-build
  8. Set a breakpoint in the ServerTask() function and press F5 to begin debugging:08-flash
  9. VisualGDB will program the FLASH memory in the ESP-WROOM-32 module and start debugging. The breakpoint will hit: 09-hit
  10.  Press F5 to continue debugging. Then locate the ESP32_VisualGDB Wi-Fi network from your device:09-wifi
  11. Once the connection is successful, open 192.168.<subnet>.1 in your browser:10-page

Congratulations! Now you customize the example to add your custom logic on top of it. You can use all other GPIO pins on the ESP-WROOM-32 module to control your peripherals as long as you reserve the MTDI, MTDO, MTMS and MTCK pins for JTAG.