AD7124 STM32 C Driver

A lightweight, robust, pure C port of the excellent epsilonrt/ad7124 Arduino library, adapted and optimized for STM32 microcontrollers using the STM32Cube HAL.

This driver supports the Analog Devices AD7124-4 and AD7124-8 24-bit Sigma-Delta ADCs, enabling high-precision measurement acquisition with minimal CPU overhead.

---

Features

• STM32 HAL Integration: Seamlessly communicates via standard HAL_SPI_Transmit and HAL_SPI_Receive API.
• Hardware/Software CS Pin Control: Features customizable multiple chip-select configurations.
• Dynamic Channel Configuration: Dynamically enable or disable channels without corrupting input pin configurations or setups.
• Single Conversion ADC Reads: Fully implemented, safe read(channel) sequence that enables a channel, samples, waits for completion, retrieves the 24-bit data register, and restores channel state.
• 24-bit Offset & Gain Calibration: Fully supports reading and writing full 24-bit calibration coefficients.
• Robust Built-in CRC-8 Validation: Real-time data validation and error-checking for high-reliability environments.
• State Corruption Prevention: Safe non-destructive bitwise updates to keep local register caches in perfect sync with the ADC hardware.

---

Getting Started

1. STM32CubeMX SPI Configuration

To communicate with the AD7124, configure your SPI peripheral in STM32CubeMX with the following parameters:

• Frame Format: Motorola
• Data Size: 8 Bits
• First Bit: MSB First
• Clock Polarity (CPOL): High (1) — AD7124 SPI Mode 3
• Clock Phase (CPHA): 2 Edge (1) — AD7124 SPI Mode 3
• Chip Select (NSS): Software-controlled (set CS pins manually as GPIO outputs)

2. Upstream Peripheral Naming

By default, the driver communicates using the hspi4 SPI handle and expects CS pins configured with the prefixes SPI4_CS_Pin/SPI4_CS_GPIO_Port in main.h.

If your STM32 project uses a different SPI peripheral (e.g., SPI1 or SPI2), declare your own handle in main.h or modify ad7124-driver.h / ad7124-driver.c to bind to your specific peripheral handle (e.g., &hspi1).

---

Code Example

Below is a typical setup and reading sequence in your main.c:

#include "ad7124.h"

int main(void) {
    // 1. Initialize system, GPIOs, and SPI
    HAL_Init();
    SystemClock_Config();
    MX_GPIO_Init();
    MX_SPI4_Init();

    // 2. Initialize AD7124 Driver
    if (begin() < 0) {
        // Initialization/Power-on timeout failed!
        Error_Handler();
    }

    // 3. Configure Setup 0 and 1
    // Setup ID: 0, Ref: Internal (2.5V), PGA: Gain 16, Polarity: Bipolar, Burnout: Off
    setConfig(0, RefInternal, Pga16, true, BurnoutOff);
    // Setup ID: 1, Ref: Internal (2.5V), PGA: Gain 16, Polarity: Bipolar, Burnout: Off
    setConfig(1, RefInternal, Pga16, true, BurnoutOff);

    // Configure filter for Setup 0 and 1
    // Setup ID: 0, Filter Type: Sinc4, FS (Data Rate): 384, Postfilter: Off, Rej60: true, Single Cycle: true
    setConfigFilter(0, Sinc4Filter, 384, NoPostFilter, true, true);
    // Setup ID: 0, Filter Type: Sinc4, FS (Data Rate): 384, Postfilter: Off, Rej60: true, Single Cycle: true
    setConfigFilter(1, Sinc4Filter, 384, NoPostFilter, true, true);

    // 4. Map i) Channel 0 to Setup 0, ii) Channel 1 to Setup 1 and Analog Inputs
    // Channel ID: 0, Setup ID: 0, Positive input: AIN2, Negative input: AIN3, Enable: false (read() enables on-demand)
    setChannel(0, 0, AIN2Input, AIN3Input, false);
    // Channel ID: 1, Setup ID: 1, Positive input: AIN4, Negative input: AIN5, Enable: false (read() enables on-demand)
    setChannel(1, 1, AIN4Input, AIN5Input, false);

    //
    (void)IntCalibration(Current1000uA);

    while (1) {
        // 5. Read Sample from Channel 0
        long raw_sample = read(0);
        
        if (raw_sample >= 0) {
            // Convert raw 24-bit two's complement value to voltage
            // gain = 16, vref = 2.5V, bipolar = true
            double voltage = toVoltage(raw_sample, 16, 2.5, true);
            
            // Print or process the voltage
            printf("Voltage: %f V\n", voltage);
        } else {
            // Read Error
            printf("Error reading channel: %ld\n", raw_sample);
        }

        HAL_Delay(1000); // Wait 1 second
    }
}

---

AD7124 Filter Settings & Datasheets

For complete register maps, noise tables, and performance specs, reference the official product pages and datasheets:

• Analog Devices AD7124-4 Datasheet (PDF)
• Analog Devices AD7124-8 Datasheet (PDF)

Filter Settings Reference Table

Below is a summarized view of standard filter configurations and their primary use cases:

Filter Type	FS Register Range	Settling Time ($t_{SETTLE}$)	Features / Noise Rejection
Sinc4	1 to 2047	$\frac{4}{f_{ADC}}$	Best noise rejection; default mode upon reset.
Sinc3	1 to 2047	$\frac{3}{f_{ADC}}$	Good balance of settling speed and rejection.
Sinc4/3 Fast	1 to 2047	$\frac{1}{f_{ADC}}$	Single-cycle settling (zero-latency).
Post Filter	N/A	$\frac{1}{f_{ADC}}$	Dynamic simultaneous 50 Hz & 60 Hz rejection.

Visual Filter Configurations Infographic

---

License & Attribution

This project is a port of the ad7124 library created by epsilonrt. In compliance with the original upstream project, this library is distributed under the CeCILL Free Software License Version 2.1 (a copyleft free software license fully compatible with the GNU GPL).

Please see the original license terms inside the upstream project or reference CeCILL-2.1 for reuse and distribution guidelines.