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ADC Design

The ADC (Analog-to-Digital Converter) on OSECHI measures analog signals from the MPPC sensor on one detection channel.

Physical Configuration

Item Value
ADC Input Pin GPIO32
Resolution 12-bit (0–4095)
Input Voltage Range 0–3.3V
Sampling Event-driven (triggered on detection only)

Hardware Jumper

The ADC input (GPIO32) is physically connected to one of the three detection channels via a hardware jumper on the PCB.

Jumper Position Connected Channel ADC outputs non-zero when
CH1 (default) Channel 1 (GPIO12) CH1 detects
CH2 Channel 2 (GPIO19) CH2 detects
CH3 Channel 3 (GPIO27) CH3 detects

The firmware reads the ADC_JUMPER_CHANNEL build flag (defined in platformio.ini) to know which channel the jumper is connected to. If the dependent channel has no detection in a given event, the ADC value is reported as 0.

If you move the jumper to a different channel, update the build flag to match:

; platformio.override.ini
[env:esp32dev-v2]
build_flags =
    -DADC_JUMPER_CHANNEL=2  ; match physical jumper position

Serial Output

The adc field appears in every detection event. With ENABLE_ADCMV=1 (default), adc_raw and adc_mv are also included:

{"type":"event","status":"ok","sent_us":1748012345678901,"hit1":85,"hit2":0,"hit3":91,"adc":2048,"adc_raw":2048,"adc_mv":1960,"detected_us":1748012345678456}
  • adc — raw 12-bit value (0–4095); 0 if the dependent channel has no detection
  • adc_mv — converted to millivolts (0–3300 mV)

Troubleshooting

Symptom Likely Cause Action
adc always 0 Dependent channel not detecting Check that the jumpered channel is receiving signals
adc always 0 Jumper position doesn't match ADC_JUMPER_CHANNEL Update build flag to match physical jumper
adc_mv missing ENABLE_ADCMV=0 in build Enable ENABLE_ADCMV=1 in platformio.override.ini