Out of tree Texas Instruments DAC7731 driver module for Zephyr RTOS

The DAC7731 is a 16-bit Digital-to-Analog Converter (DAC) which provides 16 bits of monotonic performance over the specified operating temperature range and offers a +10V internal reference.

Hardware Configuration

The DAC7731 can be configured through different pin setting. Options as below:

• DAC output range:
  The chip can be configured in a ±10V, ±5V, or +10V output range.

• Reference voltage:
  The chip has +10V internal voltage, which can be enabled or disabled. It can also use an external voltage source as reference.

• Reset behavior:
  The DAC output can be reset to either min-scale or mid-scale.

This driver module doesn't provide any capibility to change the configurations above. Please refer to the datasheet for further information if needed. The driver only consider the following pins:

• RST pin
• SPI pins
• LDAC pin

Supported Zephyr versions

• 3.6.99 (May 2024)

Usage

Module installation

Add this project to your west.yml manifest:

 # out of tree device driver
	- name: DAC7731
      path: modules/dac7731
      revision: refs/tags/zephyr-v3.6.99
      url: https://github.com/TinNotTim/dac7731_zephyr_driver

So your projects should look something like this:

manifest:
  projects:
    - name: zephyr
      url: https://github.com/zephyrproject-rtos/zephyr
      revision: refs/tags/zephyr-v3.2.0
      import: true
# out of tree device driver
    - name: DAC7731
      path: modules/dac7731
      revision: refs/tags/zephyr-v3.6.99
      url: https://github.com/TinNotTim/dac7731_zephyr_driver

This will import the driver and allow you to use it in your code.

Additionally make sure that you run west update when you've added this entry to your west.yml.

Driver configuration

Enable sensor driver subsystem and DAC7731 driver by adding these entries to your prj.conf:

CONFIG_DAC=y
CONFIG_DAC7731=y

The DAC7731 can be configured through different pin setting. Options as below:

• DAC output range:
  The chip can be configured in a ±10V, ±5V, or +10V output range.

• Reference voltage:
  The chip has +10V internal voltage, which can be enabled or disabled. It can also use an external voltage source as reference.

• Reset behavior:
  The DAC output can be reset to either min-scale or mid-scale.

This driver module doesn't provide any capibility to change the configurations above. Please refer to the datasheet for further information if needed. The driver only consider the following pins:

• RST pin
• SPI pins
• LDAC pin

Define DAC7731 in your board .overlay like this example:

&spi3 {
    status = "okay";
    pinctrl-0 = <&spi3_sck_pb3 &spi3_miso_pb4 &spi3_mosi_pb5>;
	pinctrl-names = "default";
	cs-gpios = <&gpiod 12 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>

    dac7731_1: dac7731@0 {
        compatible = "ti,dac7731";
        spi-max-frequency = <2000000>;
        reg = <0>;
        reset-gpios = <&gpiod 11 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>;
        ldac-gpios = <&gpiod 13 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>;
    };
};

Driver usage

#include <zephyr/drivers/gpio.h>
#include <zephyr/drivers/dac.h>
#include <zephyr/kernel.h>
#include <zephyr/logging/log.h>

static K_THREAD_STACK_DEFINE(dac1_thread_stack, 512);
static struct k_thread dac1_thread_data;

/* Declare the membership in registered logging module*/
LOG_MODULE_REGISTER(DAC1_TEST, CONFIG_SPI_LOG_LEVEL);

void dac1_thread(void)
{
    /* Get the device pointer to dac7731 */
	const struct device *const dac7731 = DEVICE_DT_GET_ONE(ti_dac7731);

	if (!device_is_ready(dac7731)) {
		LOG_ERR("DAC: device not ready.");
		return;
	}
	
	while (IS_ENABLED(CONFIG_DAC7731)) {      
		/* Write a 16-bit value to channel-0 to set the dac output */
		/* The driver will clip the value to 0xFFFF*/ 
		dac_write_value(dac7731, 0, 0x8000+0xFF);
		k_sleep(K_MSEC(1000));

		/* Write an arbitrary value to channel-1 to reset the dac output */
		/* The DAC API doesn't provide a dedicated reset function*/
		dac_write_value(dac7731, 1, 0);
		k_sleep(K_MSEC(1000));
	}
	k_sleep(K_FOREVER);
}


int main(void){
	
	k_thread_create(&dac1_thread_data, dac1_thread_stack,
					K_THREAD_STACK_SIZEOF(dac1_thread_stack),
					(k_thread_entry_t)dac1_thread,
					NULL, NULL, NULL,
					K_PRIO_COOP(7), 0,
					K_NO_WAIT);
	k_thread_name_set(&dac1_thread_data, "dac1_print");

	while(1){
		k_sleep(K_SECONDS(10));
	}

	return 0;
}

Relevant prj.conf:

CONFIG_DAC=y
CONFIG_DAC7731=y
CONFIG_LOG=y