GY-63_MS5611/libraries/MCP_DAC/README.md

MCP_DAC

Arduino library for Microchip SPI DAC's: 8, 10, 12 bits, 1, 2 channel.

Description

The MCP_DAC is a library for DAC's from Microchip in the MCP48xx en MCP49xx series. The library is experimental as it is not tested with all different devices. Please post an issue if there are problems.

Type	Channels	Bits	MaxValue	Voltage reference
MCP4801	1	8	255	internal 2.048 V
MCP4802	2	8	255	internal 2.048 V
MCP4811	1	10	1023	internal 2.048 V
MCP4812	2	10	1023	internal 2.048 V
MCP4821	1	12	4095	internal 2.048 V
MCP4822	2	12	4095	internal 2.048 V
MCP4901	1	8	255	external
MCP4902	2	8	255	external
MCP4911	1	10	1023	external
MCP4912	2	10	1023	external
MCP4921	1	12	4095	external
MCP4922	2	12	4095	external

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

Interface

#include "MCP_DAC.h"

Constructor

• MCP_DAC(uint8_t dataOut = 255, uint8_t clock = 255, SPIClassRP2040 *mySPI = &SPI) Constructor base class for RP2040.
• MCP_DAC(uint8_t dataOut = 255, uint8_t clock = 255, SPIClass *mySPI = &SPI) Constructor base class. Other devices just use their name as class object e.g. MCP4801 with same parameters.
• begin(uint8_t select) defines the select pin. The select pin is used for device selection in case of multiple SPI devices.
• uint8_t channels() returns the number of channels, 1 or 2. (note channel numbers are 0 or 1).
• uint16_t maxValue() returns the maximum value that can be set. This relates to the number of bits, see table above.

Gain

• bool setGain(uint8_t gain = 1) gain is 1 (default) or 2.
• uint8_t getGain() returns gain set, default 1.

The analog output cannot go beyond the supply voltage. So if Vref is connected to 5V, gain=2 will not output 10 Volts.

Write

• bool analogWrite(uint16_t value, uint8_t channel = 0) writes value to channel. Default for channel 0 as that works for the single DAC devices. The value is limited to maxValue. Returns false in case of an invalid channel.
• uint16_t lastValue(uint8_t channel = 0) returns last written value. Default for channel 0 as that works for the single DAC devices.
• void setPercentage(float percentage, uint8_t channel = 0) percentage = 0..100.0%.
  Wrapper around analogWrite().
• float getPercentage(uint8_t channel = 0) returns percentage. Reads from cache.
• void fastWriteA(uint16_t value) faster version to write to channel 0. Does not check flags and does not update lastValue()
• void fastWriteB(uint16_t value) faster version to write to channel 1. Does not check flags and does not update lastValue()
• bool increment(uint8_t channel = 0) returns true if channel is incremented, false otherwise.
• bool decrement(uint8_t channel = 0) returns true if channel is decremented, false otherwise.

For fastest speed there is an example added MCP4921_standalone.ino. That squeezes the most performance out of it for now. Code for the other MCP4xxx can be written in same way.

Shutdown

• void shutDown() shuts down the device, optional one might need to triggerLatch().
• bool isActive() returns false if device is in shutdown mode. Note: any write() operation will set active to true again.

Hardware SPI

To be used only if one needs a specific speed. Check datasheet for details.

• void setSPIspeed(uint32_t speed) set SPI transfer rate.
• uint32_t getSPIspeed() returns SPI transfer rate.

LDAC

• void setLatchPin(uint8_t latchPin) defines the latchPin, this is optional. The latchPin is used for simultaneous setting a value in both DAC registers. It can also be used to synchronize the setting of multiple devices. Note the latchPin must be the same for all instances that need to be triggered together.
• triggerLatch() toggles the defined latchPin, and all devices that are connected to it.

Note: pre 0.2.0 versions have the LDAC signal incorrectly inverted.

Buffered

MCP49xxx series only, see page 20 ==> not functional for MCP48xx series.

• void setBufferedMode(bool mode = false) set buffered mode on/off. The default mode == false == unbuffered.
• bool getBufferedMode() returns set value.

Debug

• void reset() resets internal variables to initial value. (use with care!).
• bool usesHWSPI() returns true if HW SPI is used.

ESP32 specific

SPI port selection

This functionality is new in 0.1.2 and it is expected that the interface will change in the future.

• void selectHSPI() in case hardware SPI, the ESP32 has two options HSPI and VSPI.
• void selectVSPI() see above.
• bool usesHSPI() returns true if HSPI is used.
• bool usesVSPI() returns true if VSPI is used.

The selectVSPI() or the selectHSPI() needs to be called BEFORE the begin() function.

Experimental

• void setGPIOpins(uint8_t clk, uint8_t miso, uint8_t mosi, uint8_t select) overrule GPIO pins of ESP32 for hardware SPI. Needs to be called AFTER the begin() function.

void setup()
{
  MCP.selectVSPI();
  MCP.begin(15);
  MCP.setGPIOpins(CLK, MISO, MOSI, SELECT);  // SELECT should match the param of begin()
}

This interface can change in the future as the select pin is known in the code.

ESP32 connections to MCP4922 (example)

ESP32 has four SPI peripherals from which two can be used.

SPI0 and SPI1 are used to access flash memory. SPI2 and SPI3 are "user" SPI controllers a.k.a. HSPI and VSPI.

MCP4922	HSPI = SPI2	VSPI = SPI3
CS	SELECT = 15	SELECT = 5
SCK	SCLK = 14	SCLK = 18
SDI	MOSI = 13	MOSI = 23
not used	MISO = 12	MISO = 19

By using different SELECT pins multiple DAC's can be controlled over one SPI bus.

RP2040 specific

SPI port selection

The SPI Port selections happens in the constructor with e.g. &SPI or &SPI1. For the pin swap, you need the call the experimental feature void setGPIOpins. In the constructor you need to call the parameter dataOut and clock both with 255 (0xff) or otherwise it will use SoftSPI.

Experimental

• void setGPIOpins(uint8_t clk, uint8_t miso, uint8_t mosi, uint8_t select) overrule GPIO pins of RP2040 for different SPI pins. Needs to be called AFTER the begin() function. Selected pins must match the RP2040 pinout!

Warning! This command changes the Pins of the bus not only of a specific device, but all devices, that are connected on that bus!

MCP4822 MCP(255, 255, &SPI1)

void setup()
{
  MCP.setGPIOpins(CLK, MISO, MOSI, SELECT);  // SELECT should match the param of begin()
  MCP.begin(17);
}

Pico connections to MCP4922 (example)

The RP2040 has two SPI peripherals from which two can be used.

SPI (SPI0) and SPI1 can both be used to connect devices.

MCP4922	SPI / SPI0	SPI1
CS	SELECT = 17	SELECT = 13
SCK	SCLK = 18	SCLK = 14
SDI	MOSI = 19	MOSI = 15
not used	MISO = 16	MISO = 12

By using different SELECT pins multiple DAC's can be controlled over one SPI bus.

Operation

See examples

Future

Must

• test test test and ....
• improve documentation.

Should

Could

• functional names for magic masks.
• refactor the API (how).
• minimize conditional in code if possible.
  • would this work?

#if defined(ARDUINO_ARCH_RP2040)
  #define _mySPIClass SPIClassRP2040
#else
  #define _mySPIClass SPIClass
#endif

Wont

• useSPI1 and useHSPI are functional identical indicators.
  • how to refactor to a generic model? Should work for all libraries.
  • int8_t HWSPIport = 0, 1, 2, 3, 4, .... (-1 == SW SPI ?).
    • numbers are not self-documenting.
    • selectSPIport(int) ?
  • would reduce conditional code.
  • does not improve library

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Thank you,