5.0 KiB
MCP4725
Arduino library for 12 bit I2C DAC - MCP4725.
Description
The MCP4725 is an I2C single channel 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)
RP2040 specific
There are different RP2040 board files. This library works with RP2040 pico - https://github.com/earlephilhower/arduino-pico Will give an error on setSDA() and setSCL() with the "Arduino MBED OS" version.
See remark PR #21.
- bool begin(int sda, int scl) begin communication with the DAC. It has the parameter for selecting on which pins the communication should happen. Check RP2040 Pinout for compatible pins. When Wire1 is used, it needs to be specified in the constructor with "&Wire1"
Operation
See examples
Future
Must
- update documentation
Should
- test the powerDown modes / functions.
Could
- extend unit tests