AmpWave DA1C024BS – Isolated Single Channel SPI DAC Module

In my quest for the perfect DAC for my university project, I stumbled upon the 1-channel SPI AD5420, a marvel from my homeland. Its precision in delivering configurable outputs of 0-24mA, coupled with galvanic isolation for crystal-clear signals and a swift SPI interface, was precisely what my project demanded. This module's capabilities far exceeded my hopes, positioning it as the quintessential component for my project's intricate requirements.

This galvanically isolated 1 channel SPI DAC module can be used to convert received digital signal into corresponding analog current (Range : 0-24mA, 0-20mA, 4-20mA) output accurately. The module is designed to give one analog current output which is suitable for applications where a single analog signal is required from digital input data. SPI (Serial Peripheral Interface), a common high speed interface is used for communicate between the microcontroller and the DAC module.

Why should you select this module?

• 16-bit resolution - High precision AD5420A DAC ensures smooth and highly accurate signal conversion for detailed and sensitive applications.
• Multi range current output - Software configurable 3 current ranges: 0-24 mA, 4-20mA, 0-20mA for varied applications.
• Galvanic isolation - There's no direct electrical connection between the input (SPI side) and the output (analog side).. This isolation protects the devices from electrical shocks, voltage surges, and ground loop issues, ensuring safer operation especially in sensitive or hazardous environments.
• SPI interface - Provide high speed, easy and reliable digital communication. It's work with 3.3V or 5V microcontrollers.
• Power flexibility - Supports 11 -30V supply
• Ideal for process control and automation tasks where reliable and precise analog signaling is crucial.

Connecting the ARDUINO UNO board with the DAC module

Connect the pins of both devices as follows.

• Vcc pin of DAC to 5V of Arduino uno ; this pin can be connected with both 3.3V or 5V.
• GND to GND
• FAULT pin to pin 8 of Arduino
• CLR pin to pin 9 of Arduino
• LATCH pin to pin 10 of Arduino

Code lines below define symbolic constants for specific pin numbers on the Arduino board that are connected to various control or status pins of the AD5420 digital-to-analog converter (DAC) module. The values 8, 9, and 10 can be changed to any pin numbers you wish, depending on the specific hardware setup and requirements.

#define AD5420_FAULT 8
#define AD5420_CLEAR 9
#define AD5420_LATCH 10

• SPI pins (SCLK, MOSI, MISO) on the DAC module should be connected with SPI pins on Arduino board.

MOSI (Master Out Slave In): This pin is used for data transmission from the master device (Arduino) to the slave device (such as an SPI DAC or sensor).

MISO (Master In Slave Out): This pin is used for data transmission from the slave device to the master device.

SCK (Serial Clock): This pin provides the clock signal that synchronizes data transmission between the master and slave devices.

Here are the SPI pin assignments for Arduino UNO board:

• MOSI : pin 11
• MISO : pin 12
• SCLK : pin 13

Resolution of Current DAC

The resolution of current DAC is the smallest change in analog current that can detect which is also known as the step size of the DAC. We can use the formula for the resolution of a DAC, which gives us the smallest change in output current that the DAC can produce:

Resolution = (Full scale Current) / ( 2^no of bits)

What is the step size or the minimum current output of this 1 channel SPI AD5420 DAC can detect ?

The module is 16 bit resolution with 0-24mA range. So,

Minimum Current Output = 24mA / 2^16

= 0.000366 mA

Select the current range

This DAC module have 3 output current ranges : 0-24mA, 4-20mA, 0-20mA

How we select the range that DAC should be work?

dac_ad5420.ad5420_write_ctrl(AD5420_OUTEN | AD5420_REXT | AD5420_0_24_RANGE); //AD5420 intialize (O/P Enable and Range Select)

This is the code line that enable the output and range select. To select range code line should be modified as follows.

0-24mA:

dac_ad5420.ad5420_write_ctrl(AD5420_OUTEN | AD5420_REXT | AD5420_0_24_RANGE);

0-20mA :

dac_ad5420.ad5420_write_ctrl(AD5420_OUTEN | AD5420_REXT | AD5420_0_20_RANGE);

4-20mA :

dac_ad5420.ad5420_write_ctrl(AD5420_OUTEN | AD5420_REXT | AD5420_4_20_RANGE);

OUTPUTS

After ensuring the connection of both DAC module and Arduino board the upload the code.

Open serial monitor > Type input > Send

Then connect the multimeter probes to the Iout terminal and measure the current OUTPUT. The input gives the corresponding current output. When the input is '0' DAC will outputs the minimum current value, 0mA/4mA. When the input is 'G' DAC will outputs the maximum current, 24mA/20mA.

if (Serial.available() > 0) {

    char ch = Serial.read();  // Clean the input buffer
    if (ch == '0') dac_ad5420.ad5420_write_data(0x0000);

    else if (ch == '1') dac_ad5420.ad5420_write_data(0x1000);
    else if (ch == '2') dac_ad5420.ad5420_write_data(0x2000);
    else if (ch == '3') dac_ad5420.ad5420_write_data(0x3000);
    else if (ch == '4') dac_ad5420.ad5420_write_data(0x4000);
    else if (ch == '5') dac_ad5420.ad5420_write_data(0x5000);
    else if (ch == '6') dac_ad5420.ad5420_write_data(0x6000);
    else if (ch == '7') dac_ad5420.ad5420_write_data(0x7000);
    else if (ch == '8') dac_ad5420.ad5420_write_data(0x8000);
    else if (ch == '9') dac_ad5420.ad5420_write_data(0x9000);
    else if (ch == 'A') dac_ad5420.ad5420_write_data(0xA000);
    else if (ch == 'B') dac_ad5420.ad5420_write_data(0xB000);
    else if (ch == 'C') dac_ad5420.ad5420_write_data(0xC000);
    else if (ch == 'D') dac_ad5420.ad5420_write_data(0xD000);
    else if (ch == 'E') dac_ad5420.ad5420_write_data(0xE000);
    else if (ch == 'F') dac_ad5420.ad5420_write_data(0xF000);
    else if (ch == 'G') dac_ad5420.ad5420_write_data(0xFFFF);

How to get desired current output?

To get the desired current output calculate the appropriate hexadecimal value corresponding to the desired output current and then send that value to the DAC.

dac_ad5420.ad5420_write_data(current);   //Write 0X0000 ---->O/P Current 0mA , 4mA