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

MCP_ADC

Arduino library for MCP3002 MCP3004 MCP3008 MCP3202 MCP3204 MCP3208 and compatibles.

Description

This library reads the ADC ports of the MCP ADC convertors. The chips are communicates with SPI and support both hardware SPI or optional software SPI.

type	bits	channels	notes
MCP3002	10	2
MCP3004	10	4
MCP3008	10	8
MCP3202	12	2
MCP3204	12	4
MCP3208	12	8

Current version allows manual override of the hardware SPI clock as the speed is not optimized per ADC type.

The MCP ADC allow single mode which compares voltage of a single channel against GND. Furthermore they allow a differential mode which compares two channels IN+ and IN- to each other. if the IN+ is equal or below IN- the ADC will return 0.

Build into the library is a delta mode which is a software enhanced differential mode. This delta mode can return negative values too.

Interface

If the pins are not set in the constructor, the class will automatically use the hardware SPI, otherwise it will use a software SPI.

• MCP3002(uint8_t dataIn, uint8_t dataOut, uint8_t clock) constructor 10 bit ADC 2 channel.
• MCP3004(uint8_t dataIn, uint8_t dataOut, uint8_t clock) constructor 10 bit ADC 4 channel.
• MCP3008(uint8_t dataIn, uint8_t dataOut, uint8_t clock) constructor 10 bit ADC 8 channel.
• MCP3202(uint8_t dataIn, uint8_t dataOut, uint8_t clock) constructor 12 bit ADC 2 channel.
• MCP3204(uint8_t dataIn, uint8_t dataOut, uint8_t clock) constructor 12 bit ADC 4 channel.
• MCP3208(uint8_t dataIn, uint8_t dataOut, uint8_t clock) constructor 12 bit ADC 8 channel.
• void begin(uint8_t select) set select pin.
• uint8_t channels() returns the number of channels.
• int16_t maxValue() returns maxReading of adc, e.g. 1023. This makes it easy to calculate relative measurements.
• int16_t analogRead(uint8_t channel) reads the value of a single channel.
• int16_t differentialRead(uint8_t channel) reads differential between two channels.
  Check datasheet for details.
  Note if the IN+ is equal or below IN- this function will return 0.
• int16_t deltaRead(uint8_t channel) reads differential like above however it will return a negative value if IN+ is below IN-.
• void setSPIspeed(uint32_t speed) sets SPI clock in Hz, please read datasheet of the ADC first to get optimal speed.
• uint32_t getSPIspeed() gets current speed in Hz.

Differential channel table:

Channel	diff IN+	diff IN-	MCP
0	0	1	3x02/3x04/3x08
1	1	0	3x02/3x04/3x08
2	2	3	3x04/3x08
3	3	2	3x04/3x08
4	4	5	3x08
5	5	4	3x08
6	6	7	3x08
7	7	6	3x08

debug

• bool usesHWSPI() returns true if HW SPI is used.

ESP32 specific

• 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 parameter of begin()
}

This implementation might change in the future, e.g. leave out the select pin as it is already known in the code.

About SPI Speed

See https://github.com/RobTillaart/MCP_ADC/issues/3

The default SPI speed is reduced to 1 MHz. This is the value recommended in the datasheet for 2.7V.

In a test with an ESP32 (3.3V) the library showed stable results at 4 MHz and at 6 MHz it was almost good.

The max value read at 6 MHz was 1020 instead of 1023 (MCP3008) which indicates that the last 2 bits got lost due to signal deformation.

Board	Voltage	safe	max
ESP32	2.7V	1 MHz	4 MHz
UNO	5.0V	2 MHz	4 MHz

For hardware SPI the ESP32 uses the VSPI pins. (see ESP examples).

Future

• documentation
• testing, a lot ...
• analogRead (mask, int array[8] ) read ports (set in mask) in an array in one call. would this save time?

wont

• get / setF(float A, float B) => float readF(channel) output = A*value + B; it actually does float mapping. As it implies the same mapping for all it might not be that useful => multmap

Operations

See examples.