Arduino library for the AD5620 / AD5640 Digital Analog Convertor (12/14 bit).
Experimental
The AD5620 is a 12 bit DAC, which is to be controlled by SPI. This library supports both hardware as software SPI.
The value of the DAC can be changed by setValue() or by setPercentage(). If the values are out of range these function will return false. The value set is kept by the library and can be fetched by getValue() and getPercentage().
The library also implements support for the AD5640, a 14 bit DAC.
Warning The library is not tested extensively with hardware. So it should be used with care.
Feedback, issues, improvements are welcome. Please file an issue on GitHub.
Reverted the 0.2.0 change as the 3 bytes was only for the AD5660 which is not a supported class in this library. See #12. Therefore the pre 0.3.0 versions are obsolete.
Pre 0.2.0 versions are not sending 3 bytes as they should (See #9). Therefore the pre 0.2.0 versions are obsolete.
The parts incorporate a power-on reset circuit to ensure that the DAC output powers up to
- 0 V (AD5620/AD5640/AD5660-1-2) or
- midscale (AD5620-3 and AD5660-3)
and remains there until a valid write takes place.
Overview of related devices, number of bits, setValue range and indicative LSB
| device | bits | range | % step size | LSB @ 5V | notes |
|---|---|---|---|---|---|
| AD5620 | 12 | 0..4095 | 0.025 | 1.221 mV | AD5620 library |
| AD5640 | 14 | 0..16383 | 0.0065 | 0.3053 mV | AD5620 library |
| AD5660 | 16 | 0..65535 | 0.0017 | 0.0763 mV | AD5660 library |
| AD5680 | 18 | 0..262143 | 0.0005 | 19.07 uV | AD5680 library |
- https://github.com/RobTillaart/AD5620 (single channel, 12 + 14 bit)
- https://github.com/RobTillaart/AD5660 (single channel, 16 bit)
- https://github.com/RobTillaart/AD5680 (single channel, 18 bit)
- https://github.com/RobTillaart/AD56x8 (multi channel)
- https://github.com/RobTillaart/AD568X (single channel lower resolution)
- https://github.com/RobTillaart/MCP_DAC (SPI interface)
#include "AD5620.h"The AD5640 has identical constructors.
- AD5620(uint8_t slaveSelect, SPIClassRP2040 * mySPI = &SPI) constructor hardware SPI (RP2040 specific). Sets internal value to zero.
- AD5620(uint8_t slaveSelect, SPIClass * mySPI = &SPI) constructor hardware SPI. Sets internal value to zero.
- AD5620(uint8_t slaveSelect, uint8_t spiData, uint8_t spiClock) constructor software SPI. Sets the software SPI pins. Sets internal value to zero.
- void begin() initializes the SPI and sets internal state.
- uint8_t getType() returns nr of bits, 12 for AD5620, 14 for AD5640.
- bool setValue(uint16_t value) set value to the output immediately, effectively a prepare + update in one call. Returns false if value out of range.
- uint16_t getValue() returns the set value from cache. At power up the device will be reset to 0 (== 0 volt). (not always).
- uint16_t getMaxValue() returns 4095 for AD5620, returns 16383 for AD5640.
- bool setPercentage(float percentage) sets the output as a percentage 0..100%. If percentage is out of range, it is not set and the function returns false. The step size is 0.025% for the AD5620.
- float getPercentage() returns percentage, wrapper around getValue(). Might return a slightly different value than setPercentage() due to rounding math. At power up the function will return 0 as default value.
See datasheet P19 for details.
- bool setPowerDownMode(uint8_t mode) returns false if mode is out of range.
- uint8_t getPowerDownMode() returns set power down mode, default 0.
| mode | description |
|---|---|
| 0 | normal mode (default) |
| 1 | 1 KOhm to GND |
| 2 | 100 KOhm to GND |
| 3 | ThreeState |
Adjust the performance of the SPI port.
- void setSPIspeed(uint32_t speed) sets SPI clock in Hz, please read datasheet of the ADC first to get optimal speed.
- uint32_t getSPIspeed() gets current speed in Hz.
- bool usesHWSPI() returns true if HW SPI is used.
Datasheet P7, maximum frequency. Overclocking is not tested.
| Voltage | Max Speed |
|---|---|
| 2.7 V | 20 MHz |
| 3.5 V | 20 MHz |
| 3.6 V | 30 MHz |
| 5.5 V | 30 MHz |
Measurements with AD5620_demo.ino - performance of setValue() is the most important. The numbers are rounded and indicative, other boards might produce different numbers.
| version | board | clock | SPI | calls / sec | Notes |
|---|---|---|---|---|---|
| 0.2.0 | UNO | 16 MHz | HW | 55000 | max SPI speed |
| 0.2.0 | UNO | 16 MHz | SW | 3369 | |
| 0.2.0 | ESP32 | 240 MHz | HW | ||
| 0.2.0 | ESP32 | 240 MHz | SW | ||
| 0.3.0 | UNO | 16 MHz | HW | 64000 | max SPI speed |
| 0.3.0 | UNO | 16 MHz | SW | 5100 | |
| 0.3.0 | ESP32 | 240 MHz | HW | 152500 | |
| 0.3.0 | ESP32 | 240 MHz | SW | 152500 |
(pre-0.3.0 versions obsolete)
Note UNO: 64000 calls per second means that a 1 KHz wave can be constructed with 64 values per period (max).
5100 calls per second means that a 1 KHz wave can be constructed with ~5 values per period (max).
Please share your performance data, open an issue to report.
- improve documentation
- get hardware
- test the library
- add examples
- create a similar library for AD5660
If you appreciate my libraries, you can support the development and maintenance. Improve the quality of the libraries by providing issues and Pull Requests, or donate through PayPal or GitHub sponsors.
Thank you,