MCP4725

Arduino library for 12 bit I2C DAC - MCP4725.

Description

The MCP4725 is an I2C 12 bit Digital to Analog Converter (DAC). It is possible to have up to 8 MCP4725 on one I2C bus. The MCP4725 supports 100 KHz 400 KHz and 3.4 MHz bus speeds.

The output of the MCP4725 depends on the voltage supplied, which is in the range of 2.7V .. 5.5V. Check datasheet for the details.

Interface

Constructor

MCP4725(uint8_t deviceAddress, TwoWire *wire = &Wire) Constructor, needs I2C address, optional set Wire bus
bool begin(uint8_t dataPin, uint8_t clockPin) for ESP32. Returns true if connected.
bool begin() for UNO and other boards with hard wired I2C pins. Returns true if deviceAddress can be found on the I2C bus.
bool isConnected() returns true if device (address) can be seen on the I2C bus.

base

int setValue(uint16_t value = 0) value = 0 .. 4095.
Uses writeFastMode and does not write to EEPROM. Therefore it does not update the lastWriteEEPROM timestamp. The default value is 0.
Returns 0 on success
uint16_t getValue() returns last value set from cache, this is much faster than readDAC().
This latter gives the real value from the MCP4725. Note: a difference can be caused by power outage a reset etc.
int setPercentage(float percentage) percentage = 0..100.0%. Convenience wrapper around setValue().
float getPercentage() returns percentage. Wrapper around getValue().
int writeDAC(value, bool EEPROM = false) Writes to DAC and conditionally to EEPROM.
This latter is for startup / reset behaviour. Check datasheet for the detail behaviour.
bool ready() returns true if a new value can be written to the MCP4725.
Return false if recently was written to EEPROM.
uint16_t readDAC() reads the current value set in the MCP4725.
uint16_t readEEPROM() reads the current value in the EEPROM of the MCP4725.
uint32_t getLastWriteEEPROM() returns time in millis() when last value was written to EEPROM.

Page 3 of datasheet states it takes 25 - 50 ms before values are written to EEPROM. So the exact timing of a sensor can differ quite a lot. When writing to EEPROM with writeDAC() one should check it is at least 50 ms ago. If one know the specific timing of a sensor one can tune this or even make it adaptive.

Experimental

Check datasheet for these functions, (not tested enough yet).

int writePowerDownMode(uint8_t PDM, bool EEPROM = false)
uint8_t readPowerDownModeEEPROM()
uint8_t readPowerDownModeDAC()
int powerOnReset()
int powerOnWakeUp()

More investigations needed for:

Writing to EEPROM, ready() and getLastWriteEEPROM()
checking when and how long the sensor blocks needs to be verified in detail in practice.

Address Notes

The address of the MCP4725 in the demo sketches is set to 0x62 as that was the address of the sensor I had during writing. According to the datasheet the address has the following bit pattern:

address 011000FFU (so 0x6?)

     F = Factory set bit
     U = User configurable bit

This means you can have at most 8 MCP4725 in one I2C bus (without multiplexing). You have to specify the factory bits in your order, but not all shops might provide all versions of the MCP4725.

MCP4725A0T-E/CH:  0110 000U   0x60 - 0x61
MCP4725A1T-E/CH:  0110 001U   0x62 - 0x63
MCP4725A2T-E/CH:  0110 010U   0x64 - 0x65
MCP4725A3T-E/CH:  0110 011U   0x66 - 0x67

If one need more DAC's one might have a look at the MCP4728 It has 4 channels per chip (no experience /library yet)

Operation

See examples

Future

update documentation
test the powerDown modes / functions.
write a sketch to measure the writeDac() timing if possible.
extend unit tests

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