GY-63_MS5611/libraries/MCP_ADC/README.md
2022-11-17 13:00:17 +01:00

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# 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.
```cpp
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).
## Operations
See examples.
## Future
#### must
- documentation
- testing, a lot ...
#### should
#### could
- 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 => multimap