Esp32 Workbench Gpio

ESP32 GPIO Control

Base URL: http://192.168.0.87:8080

Endpoints

Allowed BCM Pins

5, 6, 12, 13, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27

Pin Values

Only use 0 (low) and 1 (high). Release = drive HIGH (1).

Pin Mapping

Examples

# Drive GPIO18 LOW (hold BOOT button)
curl -X POST http://192.168.0.87:8080/api/gpio/set \
  -H 'Content-Type: application/json' \
  -d '{"pin": 18, "value": 0}'

# Drive GPIO18 HIGH (release)
curl -X POST http://192.168.0.87:8080/api/gpio/set \
  -H 'Content-Type: application/json' \
  -d '{"pin": 18, "value": 1}'

# Read all driven pin states
curl http://192.168.0.87:8080/api/gpio/status

Common Workflows

1. Enter ESP32 download mode (hold BOOT during reset):

   # 1. Hold BOOT (GPIO18) LOW
   curl -X POST http://192.168.0.87:8080/api/gpio/set \
     -H 'Content-Type: application/json' -d '{"pin": 18, "value": 0}'
   sleep 1
   # 2. Pull EN (GPIO17) LOW — assert reset
   curl -X POST http://192.168.0.87:8080/api/gpio/set \
     -H 'Content-Type: application/json' -d '{"pin": 17, "value": 0}'
   sleep 0.2
   # 3. Release EN HIGH — ESP32 exits reset, samples BOOT=LOW → download mode
   curl -X POST http://192.168.0.87:8080/api/gpio/set \
     -H 'Content-Type: application/json' -d '{"pin": 17, "value": 1}'
   sleep 0.5
   # 4. Release BOOT HIGH
   curl -X POST http://192.168.0.87:8080/api/gpio/set \
     -H 'Content-Type: application/json' -d '{"pin": 18, "value": 1}'
   

2. Flash after GPIO download mode:

   # Wait 5s for USB re-enumeration after GPIO reset
   sleep 5
   esptool.py --port "rfc2217://192.168.0.87:<PORT>?ign_set_control" \
     --chip esp32s3 --before=no_reset write_flash 0x0 firmware.bin
   

3. Normal reset (without entering download mode):

   curl -X POST http://192.168.0.87:8080/api/gpio/set \
     -H 'Content-Type: application/json' -d '{"pin": 17, "value": 0}'
   sleep 0.2
   curl -X POST http://192.168.0.87:8080/api/gpio/set \
     -H 'Content-Type: application/json' -d '{"pin": 17, "value": 1}'
   

4. Simulate button press:

   • Set pin LOW, wait, set pin HIGH (1) to release

GPIO Control Probe — Auto-Detecting Board Capabilities

Not all boards have EN/BOOT pins wired to Pi GPIOs. Run this probe once per board.

Probe Procedure

# Step 1: Try GPIO-based download mode entry
curl -X POST http://192.168.0.87:8080/api/gpio/set \
  -H 'Content-Type: application/json' -d '{"pin": 18, "value": 0}'
sleep 1
curl -X POST http://192.168.0.87:8080/api/gpio/set \
  -H 'Content-Type: application/json' -d '{"pin": 17, "value": 0}'
sleep 0.2
curl -X POST http://192.168.0.87:8080/api/gpio/set \
  -H 'Content-Type: application/json' -d '{"pin": 17, "value": 1}'
sleep 0.5
curl -X POST http://192.168.0.87:8080/api/gpio/set \
  -H 'Content-Type: application/json' -d '{"pin": 18, "value": 1}'

# Monitor for boot output
curl -X POST http://192.168.0.87:8080/api/serial/monitor \
  -H 'Content-Type: application/json' \
  -d '{"slot": "<slot>", "pattern": "boot:", "timeout": 3}'

# Step 2: If GPIO had no effect, try USB DTR/RTS reset
curl -X POST http://192.168.0.87:8080/api/serial/reset \
  -H 'Content-Type: application/json' -d '{"slot": "<slot>"}'

Interpreting Results

Caveats

• Firmware crash loops (rst:0xc) mask GPIO resets. Erase flash first with esptool.py --before=usb_reset erase_flash, then re-run the probe.
• Dual-USB hub boards always respond to USB DTR/RTS on the JTAG slot; GPIO probe will show no effect.
• Probe only needs to run once per physical board.

Note: Dual-USB Hub Boards

Some ESP32-S3 dev boards have an onboard USB hub with a built-in auto-download circuit that connects GPIO0/EN to DTR/RTS on the USB-Serial/JTAG interface. For these boards, external Pi GPIO wiring is not needed — DTR/RTS on the JTAG slot handles reset and download mode via POST /api/serial/reset.

Troubleshooting