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Edge101 Industrial ESP32 IoT Programmable Controller

40PIN GPIOs and BLINK-LED

The article details the 40P GPIO interface on Edge101, explaining its configurations, capabilities, and multiplexing functions, and provides practical guidance on controlling an onboard LED using sample code.

GPIO

The 40-pin expansion interface on the Edge101 mainboard provides 11 GPIOs and is equipped with Gravity 3-pin and 4-pin I2C interfaces, allowing direct connection to DFRobot's Gravity devices.

The GPIOs support internal pull-up, pull-down, or high-impedance configurations. When used as inputs, the values can be read through registers, and they support edge or level-triggered CPU interrupts.

All IO pins are bidirectional, non-inverting, and tri-state designed, supporting input, output, and tri-state control functions. Additionally, they can be multiplexed for other functions such as SDIO, UART, and SPI.

40PIN Expansion Interface Diagram

40PIN Expansion Interface Diagram

Pin Name GPIO Function ADC Function Communication Function Multiplexing Function
P5 GPIO5, supports input/output SPICS0 Gravity SPICS0
P12 GPIO12, supports input/output ADC2_CH5 SPI-SDO Gravity SPI-SDO
P14 GPIO14, supports input/output ADC2_CH6 SPI-CLK Gravity SPI-CLK
P15 GPIO15, supports input/output ADC2_CH3 Onboard LED
P18 GPIO18, supports input/output I2C-SDA Gravity I2C-SDA
P23 GPIO23, supports input/output I2C-SCL Gravity I2C-SCL
P33 GPIO33, supports input/output U1TXD PCIe Slot U1TXD
P34 GPIO34, input only U1RXD PCIe Slot U1RXD
P37 GPIO37, input only ADC1_CH1
P38 GPIO38, input only ADC1_CH2 Onboard Button
P39 GPIO39, input only ADC1_CH3 SPI-SDI Gravity SPI-SDI

Note:

  • GPIO34 to GPIO38 can only be used as inputs and do not support PULLUP or PULLDOWN modes. When using analog input, you must use the GPIOs connected to the ADC. However, if you use wireless communication such as Wi-Fi, ADC 2 will be unavailable.
  • The following GPIOs have built-in pull-up or pull-down resistors:
    • GPIO0: Internal pull-up
    • GPIO5: Internal pull-up
    • GPIO12: Internal pull-down (Default setting ensures FLASH operates at 3.3V. Forcing an external pull-up may cause the board to malfunction.)

Example: Controlling the LED

Set P38 (connected to the onboard button) as an input and P15 (connected to the onboard LED) as an output. When the button is pressed, the LED lights up.

Hardware Preparation:

Sample Code:

const int buttonPin = 38;   // GPIO38 for the onboard button
const int ledPin =  15;     // GPIO15 for the onboard LED

// Variable will change
int buttonState = 0;        // Use a variable to store the button state

void setup() {
   // If the external circuit does not have a pull-up or pull-down resistor,
   // enable the internal pull-up or pull-down resistor when using GPIO as an input
   // to accurately detect the signal level.

   // Initialize button pin as input without enabling pull-up or pull-down
   pinMode(buttonPin, INPUT);

   // Initialize button pin as input with pull-up enabled
   // pinMode(buttonPin, INPUT_PULLUP);

   // Initialize button pin as input with pull-down enabled
   // pinMode(buttonPin, INPUT_PULLDOWN);
      
  pinMode(ledPin, OUTPUT);     // Initialize LED pin as output
  pinMode(buttonPin, INPUT);   // Initialize button pin as input
}

void loop() {
  // Read the button state
  buttonState = digitalRead(buttonPin);

  // If the button input is LOW, the button is pressed, and the onboard green user LED will turn on
  if (buttonState == LOW) {
    // Turn on the LED
    digitalWrite(ledPin, LOW);
  } else {
    // Turn off the LED
    digitalWrite(ledPin, HIGH);
  }
}

Result:

When the button KEY (P38) is pressed, the LED (P15) lights up. When the button is released, the LED turns off.

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