GY-63_MS5611/libraries/DAC8571

DAC8571

Arduino library for DAC8571 I2C 16 bit DAC.

Description

Experimental

The DAC8571 is a small low-power, 16-bit voltage Power-On Reset to Zero output DAC.

The DAC8571 has one 16 bit DAC. The output value can be set from 0..65535. This results in a voltage which depends on a reference voltage Vref (datasheet). At power up it always will start with a value of zero.

The DAC8571 has a temporary register in which a value can be preloaded. This can be used to change the DAC at a later moment.

Not supported is the broadcast function to change multiple DAC8571 (and compatibles) at the same moment by using this temporary register.

As said the library is experimental need to be tested with hardware. Feedback is always welcome, please open an issue.

Settling time

From datasheet page 24.

Settling time to within the 16-bit accurate range of the DAC8571 is achievable within 10 μs for a full-scale code change at the input. Worst case settling times between consecutive code changes is typically less than 2 μs, therefore, the update rate is limited by the I2C interface.

I2C

Address

The DAC8571 support 2 addresses by means of an A0 address pin.

Address	A0
0x4C	LOW
0x4E	HIGH

It might be possible to connect this address pin to an IO pin and keep only one HIGH and remaining LOW to support many devices. This is not tested, feedback welcome.

I2C performance

Extend table, use output of DAC8571_performance.ino

Time in microseconds.
array == write(array, length) Assumption all write modi have similar performance.

Tested on Arduino UNO.

Speed	function	time	notes
100000	write()
100000	read()
200000	write()
200000	read()
400000	write()
400000	read()

Test ESP32 (Kudos to Paul)

Speed	write()	read()	write(array)	Notes
50000	800.01	800.04
100000	439.02	441.18	2100.01	array == 10 elements!
200000	239.12	242.41	1090.82
300000	178.05	181.81	757.57
400000	148.94	156.83	595.24
500000	131.57	142.93	497.99
600000	120.68	136.35	428.59
700000	113.19	130.40	384.64
800000	108.12	128.18	351.85
900000	98.21	106.67	317.45
1000000	94.11	94.58	296.88

I2C multiplexing

Sometimes you need to control more devices than possible with the default address range the device provides. This is possible with an I2C multiplexer e.g. TCA9548 which creates up to eight channels (think of it as I2C subnets) which can use the complete address range of the device.

Drawback of using a multiplexer is that it takes more administration in your code e.g. which device is on which channel. This will slow down the access, which must be taken into account when deciding which devices are on which channel. Also note that switching between channels will slow down other devices too if they are behind the multiplexer.

• https://github.com/RobTillaart/TCA9548

Related

• https://github.com/RobTillaart/AD5680 (18 bit DAC)
• https://github.com/RobTillaart/DAC8550
• https://github.com/RobTillaart/DAC8551
• https://github.com/RobTillaart/DAC8552
• https://github.com/RobTillaart/DAC8554
• https://github.com/RobTillaart/DAC8571
• https://github.com/RobTillaart/MCP_DAC
• https://github.com/RobTillaart/MCP_ADC

Interface

#include "DAC8571.h"

Constructor

• DAC8571(uint8_t address = 0x4C, TwoWire *wire = &Wire) constructor with I2C address. Default is 0x4C, optional set the WireN I2C bus.
• bool begin(uint16_t value = 0) Set initial value for the DAC, typical zero (power on default). Returns false if address out of range, or if device cannot be seen on the I2C bus. Returns true if successful.
• bool isConnected() test to see if address can be reached on the I2C bus.
• uint8_t getAddress() returns address set in constructor.

Core

The DAC8571 has one 16 bit DAC. The output value can be set from 0..65535.

• bool write(uint16_t value) writes a value 0..65535 to the DAC. NO default, user must explicit set value.
• uint16_t lastWrite() get last value written from cache (fast).
• uint16_t read() get last written value from device.

Percentage wrappers

• void setPercentage(float perc) set 0.00 .. 100.00
• float getPercentage() returns 0.0 .. 100.0

Write modi

The DAC8571 can be written in different modi (datasheet page 19). Not all modi are supported yet, these need testing.

• void setWriteMode(uint8_t mode = DAC8571_MODE_NORMAL)
• uint8_t getWriteMode()

Setting the mode will be applied for all writes until mode is changed.

Mode	Meaning
DAC8571_MODE_STORE_CACHE	store value in temporary register. Preparation for (2, 3 and 4)
DAC8571_MODE_NORMAL	update DAC with value written. DEFAULT.
DAC8571_MODE_WRITE_CACHE	writes the temporary register to DAC, ignores new value.
DAC8571_MODE_BRCAST_0	broadcast update. Not supported yet. See below.
DAC8571_MODE_BRCAST_1	broadcast update. Not supported yet. See below.
DAC8571_MODE_BRCAST_2	broadcast update. Not supported yet. See below.
other	maps onto default DAC8571_MODE_NORMAL.

Write multiple values - High speed mode.

The maximum length depends on the internal I2C BUFFER of the board. For Arduino this is typical 32 bytes so it allows 14 values.

• void write(uint16_t arr[n], uint8_t length) Writes a buffer with max 14 values in one I2C call. The last value written will be remembered in lastWrite().

Power Down mode

To investigate: Mixes also with broadcast ==> complex API.

• void powerDown(uint8_t pdMode = 0) default low power.
• void wakeUp(uint16_t value = 0) wake up, DAC value set to zero by default.

See table 6, page 22 datasheet for details.

Power Down Mode	Meaning
DAC8571_PD_LOW_POWER	170 uA
DAC8571_PD_FAST	250 uA
DAC8571_PD_1_KOHM	200 nA, GND 1 KOhm
DAC8571_PD_100_KOHM	200 nA, GND 100 KOhm
DAC8571_PD_HI_Z	200 nA, open circuit, high impedance

Broadcast mode

Not supported

Different ways possible, need to investigate API. (page 19)

Three broadcast commands exists:

Mode	Meaning
DAC8571_MODE_BRCAST_0	Load all devices from temporary register
DAC8571_MODE_BRCAST_1	Load all devices with data.
DAC8571_MODE_BRCAST_2	Power down all devices

Error codes

• int lastError() always check this value after a read() / write() to see if it was DAC8571_OK. After the call to lastError() the error value is reset to DAC8571_OK.

Error code	Value	Notes
DAC8571_OK	0x00
DAC8571_I2C_ERROR	0x81
DAC8571_ADDRESS_ERROR	0x82
DAC8571_BUFFER_ERROR	0x83	write(arr, length) length error

Future

Must

• get hardware to test
• improve documentation
• test different write modi

Should

• extend performance table
• replace magic numbers

Could

• add examples
• investigate broadcast support
• investigate known compatibles
  • including SPI versions?

Wont

Support

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Thank you,