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GPIO Pinout

Pin allocation for the OSECHI cosmic ray detector on ESP32-WROOM-32E.

┌─────────────────┐
│ ESP32-WROOM-32E │
│                 │
│      GPIO12 ────┤──── Detection CH1
│      GPIO19 ────┤──── Detection CH2
│      GPIO27 ────┤──── Detection CH3
│                 │
│      GPIO14 ────┤──── LED CH1
│      GPIO26 ────┤──── LED CH2
│      GPIO33 ────┤──── LED CH3
│                 │
│      GPIO32 ────┤──── ADC Input
│                 │
│      GPIO5  ────┤──── DAC CS CH1 (SPI)
│      GPIO13 ────┤──── DAC CS CH2 (SPI)
│      GPIO15 ────┤──── DAC CS CH3 (SPI)
│      GPIO23 ────┤──── DAC MOSI  (SPI)
│      GPIO18 ────┤──── DAC CLK   (SPI)
│                 │
│      GPIO21 ────┤──── BME280 SDA (I2C)
│      GPIO22 ────┤──── BME280 SCL (I2C)
│                 │
│   RXD0/TXD0 ────┤──── Serial (USB)
└─────────────────┘

Pin Allocation Table

Detection Channels

GPIO Direction Connected To Description
GPIO12 Input Comparator CH1 Cosmic ray detection channel 1
GPIO19 Input Comparator CH2 Cosmic ray detection channel 2
GPIO27 Input Comparator CH3 Cosmic ray detection channel 3

LED Feedback

GPIO Direction LED Color Description
GPIO14 Output Red Lights up when CH1 detects
GPIO26 Output Green Lights up when CH2 detects
GPIO33 Output Blue Lights up when CH3 detects

ADC Input

GPIO Direction Connected To Description
GPIO32 Analog input MPPC sensor (via jumper) Analog signal from one detection channel

See ADC Design for jumper configuration details.

SPI — DAC Threshold Control

GPIO Direction Connected To Description
GPIO23 Output DAC MOSI Data to DAC chips
GPIO18 Output DAC CLK SPI clock
GPIO5 Output DAC CS1 Chip select for DAC CH1
GPIO13 Output DAC CS2 Chip select for DAC CH2
GPIO15 Output DAC CS3 Chip select for DAC CH3

MISO not used

The DAC chip (MCP4811T) is write-only and does not send data back. Although the ESP32 SPI controller assigns GPIO19 as MISO by default, no data is ever received on that line. Detection CH2 on GPIO19 is unaffected.

I2C — Environmental Sensor

GPIO Direction Connected To Description
GPIO21 Output BME280 SDA BME280 data line
GPIO22 Output BME280 SCL BME280 clock line

BME280 I2C address: 0x76

Serial Communication

GPIO Direction Connected To Description
GPIO1 Output UART TX Serial output to PC
GPIO3 Input UART RX Serial input from PC

Baud rate: 115200. Connected via USB through the onboard CH340 USB-UART bridge.

References