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125 lines
4.8 KiB
Markdown
125 lines
4.8 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/MCP4725/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/MCP4725/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/MCP4725/blob/master/LICENSE)
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[](https://github.com/RobTillaart/MCP4725/releases)
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# MCP4725
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Arduino library for 12 bit I2C DAC - MCP4725.
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## Description
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The MCP4725 is an I2C 12 bit Digital to Analog Converter (DAC).
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It is possible to have up to 8 MCP4725 on one I2C bus.
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The MCP4725 supports 100 KHz 400 KHz and 3.4 MHz bus speeds.
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The output of the MCP4725 depends on the voltage supplied, which is in the range
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of 2.7V .. 5.5V. Check datasheet for the details.
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## Interface
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### Constructor
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- **MCP4725(uint8_t deviceAddress, TwoWire \*wire = &Wire)** Constructor, needs I2C address, optional set Wire bus
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- **bool begin(uint8_t dataPin, uint8_t clockPin)** for ESP32. Returns true if connected.
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- **bool begin()** for UNO and other boards with hard wired I2C pins.
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Returns true if deviceAddress can be found on the I2C bus.
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- **bool isConnected()** returns true if device (address) can be seen on the I2C bus.
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### base
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- **int setValue(uint16_t value = 0)** value = 0 .. 4095.
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Uses writeFastMode and does not write to EEPROM.
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Therefore it does not update the lastWriteEEPROM timestamp.
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The default value is 0.
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Returns 0 on success
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- **uint16_t getValue()** returns last value set from cache, this is much faster than readDAC().
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This latter gives the real value from the MCP4725.
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Note: a difference can be caused by power outage a reset etc.
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- **int setPercentage(float percentage)** percentage = 0..100.0%.
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Convenience wrapper around setValue().
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- **float getPercentage()** returns percentage. Wrapper around getValue().
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- **int writeDAC(value, bool EEPROM = false)** Writes to DAC and conditionally to EEPROM.
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This latter is for startup / reset behaviour. Check datasheet for the detail behaviour.
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- **bool ready()** returns true if a new value can be written to the MCP4725.
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Return false if recently was written to EEPROM.
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- **uint16_t readDAC()** reads the current value set in the MCP4725.
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- **uint16_t readEEPROM()** reads the current value in the EEPROM of the MCP4725.
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- **uint32_t getLastWriteEEPROM()** returns time in millis() when last value was written to EEPROM.
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Page 3 of datasheet states it takes **25 - 50 ms** before values are written to EEPROM.
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So the exact timing of a sensor can differ quite a lot.
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When writing to EEPROM with **writeDAC()** one should check it is at least 50 ms ago.
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If one know the specific timing of a sensor one can tune this or even make it adaptive.
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## Experimental
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Check datasheet for these functions, (not tested enough yet).
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- **int writePowerDownMode(uint8_t PDM, bool EEPROM = false)**
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- **uint8_t readPowerDownModeEEPROM()**
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- **uint8_t readPowerDownModeDAC()**
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- **int powerOnReset()**
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- **int powerOnWakeUp()**
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More investigations needed for:
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- Writing to EEPROM, **ready()** and **getLastWriteEEPROM()**
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checking when and how long the sensor blocks needs to be verified in detail in practice.
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## Address Notes
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The address of the MCP4725 in the demo sketches is set to 0x62 as that
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was the address of the sensor I had during writing.
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According to the datasheet the address has the following bit pattern:
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address 011000FFU (so 0x6?)
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F = Factory set bit
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U = User configurable bit
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This means you can have at most 8 MCP4725 in one I2C bus (without multiplexing).
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You have to specify the factory bits in your order, but not all shops might
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provide all versions of the MCP4725.
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```
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MCP4725A0T-E/CH: 0110 000U 0x60 - 0x61
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MCP4725A1T-E/CH: 0110 001U 0x62 - 0x63
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MCP4725A2T-E/CH: 0110 010U 0x64 - 0x65
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MCP4725A3T-E/CH: 0110 011U 0x66 - 0x67
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```
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If one need more DAC's one might have a look at the MCP4728
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It has 4 channels per chip (no experience /library yet)
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### RP2040 specific
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- **bool begin(int sda, int scl)** begin communication with the DAC.
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It has the parameter for selecting on which pins the communication should happen.
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Check RP2040 Pinout for compatible pins.
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When Wire1 is used, it needs to be specified in the constructor with "&Wire1"
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## Operation
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See examples
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## Future
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- update documentation
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- test the powerDown modes / functions.
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- write a sketch to measure the **writeDac()** timing if possible.
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- extend unit tests
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-
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