ESP32 Load Cell Integration#

You:#

15:06

I’d like to connect 4 loads cells to a AD7124-8 circuit which is connected to an ESP32-WROOM via SPI. Every 100ms a sample comprising 4 readings (a value of each load cell) shall be sent via Bluetooth.

ChatGPT:#

15:07

To achieve this setup, you’ll need to follow several steps to connect and configure the components properly. Here’s a step-by-step guide:

1. Hardware Connections#

Load Cells: Each load cell has four wires: Excitation+ (E+), Excitation- (E-), Signal+ (S+), and Signal- (S-).
- Connect E+ and E- of all load cells to the same power supply (typically 5V for E+ and GND for E-).
- Connect the S+ and S- of each load cell to the differential input channels of the AD7124-8. This ADC has multiple differential input pairs, so connect each load cell to a different pair of inputs.
AD7124-8 (ADC):
- Connect the SPI lines (MISO, MOSI, SCLK, and CS) of the AD7124-8 to the corresponding pins on the ESP32-WROOM.
- Ensure proper power supply and ground connections between the ESP32, AD7124-8, and the load cells.
- Refer to the AD7124-8 datasheet to properly configure the analog inputs for differential measurements and set the appropriate gain for the load cell signals.
ESP32-WROOM:
- Use the SPI interface to communicate with the AD7124-8.
- The Bluetooth module of the ESP32 will be used to send data.

2. Software Configuration#

ESP32 Code#

Initialize SPI Communication:
- Set up the SPI bus on the ESP32 to communicate with the AD7124-8.
- Configure the SPI settings (mode, clock speed, etc.) as required by the AD7124-8.
Configure AD7124-8:
- Initialize the AD7124-8 and configure it for reading the four load cells. This includes setting the appropriate channels, gain, filter, and reference voltage.
- You may need to write specific register values to configure the ADC channels. Check the AD7124-8 datasheet for details.
Sampling Loop:
- Create a loop to read the ADC values from the AD7124-8 every 100ms.
- Read each load cell’s value from its corresponding channel.
- Store these readings in a data structure.
Bluetooth Communication:
- Initialize the Bluetooth interface on the ESP32 using the Arduino or ESP-IDF libraries.
- Send the collected data over Bluetooth. You can format the data as a simple string, JSON, or another format suitable for your application.
Timing:
- Use a timer or delay function to ensure that the sampling and Bluetooth sending loop runs every 100ms.

Example Pseudocode#

#include <SPI.h>
#include <BluetoothSerial.h>

#define CS_PIN 5  // Chip Select pin for SPI
BluetoothSerial SerialBT;

void setup() {
    // Initialize SPI and Bluetooth
    SPI.begin();
    pinMode(CS_PIN, OUTPUT);
    SerialBT.begin("LoadCellData");

    // Initialize AD7124-8
    initializeAD7124();
}

void loop() {
    static unsigned long lastTime = 0;
    if (millis() - lastTime >= 100) {
        lastTime = millis();
        int32_t loadCell1 = readADC(0);  // Read channel 0
        int32_t loadCell2 = readADC(1);  // Read channel 1
        int32_t loadCell3 = readADC(2);  // Read channel 2
        int32_t loadCell4 = readADC(3);  // Read channel 3

        // Create a data packet to send via Bluetooth
        String data = String(loadCell1) + "," + String(loadCell2) + "," + String(loadCell3) + "," + String(loadCell4);
        SerialBT.println(data);
    }
}

void initializeAD7124() {
    // Implement AD7124 initialization code here
}

int32_t readADC(uint8_t channel) {
    // Implement ADC reading code here based on channel
    int32_t result = 0;
    digitalWrite(CS_PIN, LOW);
    // SPI transaction to read from AD7124-8
    //...
    digitalWrite(CS_PIN, HIGH);
    return result;
}

3. Testing and Calibration#

Calibration: You’ll need to calibrate each load cell to convert the raw ADC values into meaningful weight measurements. This typically involves applying known weights to the load cells and calculating calibration coefficients.
Testing: Run your code and test the setup to ensure that data is being read correctly from each load cell and transmitted via Bluetooth.

You:#

15:07

Let’s create a PlatformIO project from it.

ChatGPT:#

15:08

To create a PlatformIO project for your setup, follow these steps:

1. Set Up PlatformIO#

If you haven’t already installed PlatformIO, you’ll need to install it. PlatformIO can be installed as an extension in Visual Studio Code or as a standalone CLI tool.

For Visual Studio Code:
1. Open Visual Studio Code.
2. Go to the Extensions view by clicking on the Extensions icon in the Activity Bar on the side of the window.
3. Search for “PlatformIO IDE” and install it.
4. After installation, PlatformIO will be available in the bottom-left corner of Visual Studio Code.
For CLI:
1. Install Python (if not already installed).
2. Run the following command in your terminal:
```
pip install platformio
```

2. Create a New PlatformIO Project#

Open Visual Studio Code and go to the PlatformIO Home (click on the PlatformIO icon in the bottom-left corner).
Click on “New Project”.
Configure the new project:
- Name: Give your project a name (e.g., LoadCellProject).
- Board: Select ESP32 Dev Module (which corresponds to the ESP32-WROOM).
- Framework: Choose Arduino.
- Location: Choose where you want to save the project.
Click Finish.

3. Write the Code#

After creating the project, PlatformIO will generate a directory structure. Write the code into the src/main.cpp file.

main.cpp#

#include <Arduino.h>
#include <SPI.h>
#include <BluetoothSerial.h>

#define CS_PIN 5  // Chip Select pin for SPI

BluetoothSerial SerialBT;

void setup() {
    // Initialize Serial for debugging
    Serial.begin(115200);

    // Initialize SPI
    SPI.begin();
    pinMode(CS_PIN, OUTPUT);

    // Initialize Bluetooth
    SerialBT.begin("LoadCellData");

    // Initialize AD7124-8
    initializeAD7124();

    Serial.println("Setup Complete");
}

void loop() {
    static unsigned long lastTime = 0;
    if (millis() - lastTime >= 100) {
        lastTime = millis();

        // Read data from ADC channels
        int32_t loadCell1 = readADC(0);  // Read channel 0
        int32_t loadCell2 = readADC(1);  // Read channel 1
        int32_t loadCell3 = readADC(2);  // Read channel 2
        int32_t loadCell4 = readADC(3);  // Read channel 3

        // Create a data packet to send via Bluetooth
        String data = String(loadCell1) + "," + String(loadCell2) + "," + String(loadCell3) + "," + String(loadCell4);
        SerialBT.println(data);
        Serial.println(data); // Also print to Serial for debugging
    }
}

void initializeAD7124() {
    // Implement AD7124 initialization code here
    // e.g., Configure registers for channel settings
}

int32_t readADC(uint8_t channel) {
    // Implement ADC reading code here based on the selected channel
    int32_t result = 0;

    digitalWrite(CS_PIN, LOW);
    // SPI transaction to read from AD7124-8
    // Example: result = SPI.transfer16(...);
    digitalWrite(CS_PIN, HIGH);

    return result;
}

4. Configure PlatformIO Environment#

PlatformIO uses a platformio.ini file for configuration. PlatformIO should generate a basic platformio.ini file when you create a new project. Here’s a minimal configuration for your ESP32 project:

platformio.ini#

[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200

This configuration specifies the platform (Espressif32), the board (ESP32 Dev Module), the framework (Arduino), and the serial monitor speed.

5. Build and Upload the Project#

Build the Project: Click on the checkmark icon in the bottom bar of Visual Studio Code or use the command palette (Ctrl + Shift + P) and search for “PlatformIO: Build”.
Upload the Project: Click on the arrow icon in the bottom bar or use the command palette to search for “PlatformIO: Upload”. Ensure your ESP32 is connected to your computer via USB.

6. Monitor Serial Output#

To monitor the serial output for debugging, click on the plug icon in the bottom bar or use the command palette and search for “PlatformIO: Serial Monitor”.

7. Testing and Debugging#

Make sure that the ESP32 is connected properly, and the Bluetooth device is discoverable.
Connect to the ESP32 using a Bluetooth-enabled device to receive the data stream.
Use the Serial Monitor in PlatformIO to view debug output and ensure that the system is functioning correctly.

With this setup, your ESP32 should read data from the AD7124-8 every 100ms and send it via Bluetooth.

You:#

15:10

It’s just a question, please don’t change anything based on that question yet:

Since I can’t see any pairing of Bluetooth connection in this setup one or more devices can just receive the signals, right?

ChatGPT:#

15:10

Yes, in the current setup, the ESP32 is acting as a Bluetooth Serial (Bluetooth SPP) device that broadcasts data. Since there’s no explicit pairing or authentication process in the code, any Bluetooth-enabled device within range that knows how to listen to the Bluetooth Serial output could potentially receive the data. This setup is essentially an open broadcast, meaning that multiple devices can receive the transmitted data simultaneously, provided they are within range and have connected to the ESP32’s Bluetooth serial stream.

If you want to restrict access, you’d typically implement Bluetooth pairing or add some form of encryption or authentication in the communication process.

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Tags

ESP32 Load Cell Integration#

You:#

ChatGPT:#

1. Hardware Connections#

2. Software Configuration#

ESP32 Code#

Example Pseudocode#

3. Testing and Calibration#

4. Optimization and Refinement#

You:#

ChatGPT:#

1. Set Up PlatformIO#

2. Create a New PlatformIO Project#

3. Write the Code#

main.cpp#

4. Configure PlatformIO Environment#

platformio.ini#

5. Build and Upload the Project#

6. Monitor Serial Output#

7. Testing and Debugging#

You:#

ChatGPT:#