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- #include "Port_MCP23S17.h"
-
- /* transfer() writes data to registerAddr, reads portSate from registerAddr, and returns portState.
-
- MCP23S17 SPI interface is 10 MHz max.
- The electrical limitation to bus speed is bus capacitance and the length of the wires involved.
- Longer wires require lower clock speeds.
- */
- uint8_t Port_MCP23S17::transfer(const uint8_t command, const uint8_t registerAddr,
- const uint8_t data)
- {
- uint8_t portState; //bit pattern
-
- SPI.beginTransaction( SPISettings(5000000, MSBFIRST, SPI_MODE0) ); //control SPI bus, 5 MHz
- digitalWrite(SS, LOW); //enable Slave Select
- SPI.transfer(command); //write or read command
- SPI.transfer(registerAddr); //register address to write data to
- portState = SPI.transfer(data); //write data, read portState
- digitalWrite(SS, HIGH); //disable Slave Select
- SPI.endTransaction();
-
- return portState;
- }
-
- /* begin() is called from Scanner_IOE::begin(). Initiates SPI bus.
- */
- void Port_MCP23S17::beginProtocol()
- {
- pinMode(SS, OUTPUT); //configure controller's Slave Select pin to output
- digitalWrite(SS, HIGH); //disable Slave Select
- SPI.begin();
- }
-
- /* begin() is called from Scanner_IOE::begin().
- strobeOn is logic level of strobe on, HIGH or LOW
- configure IODIR and GPPU.
- */
- void Port_MCP23S17::begin(const uint8_t strobeOn)
- {
- uint8_t pullUp; //bits, GPPU 0=pull-up disabled, 1=pull-up enabled
-
- if (strobeOn == LOW) //if active low, use internal pull-up resistors
- {
- pullUp = readPins;
- }
- else //active high requires external pull-down resistors
- {
- pullUp = 0;
- }
-
- transfer(deviceAddr << 1, portNum, readPins); //configure IODIR
- transfer(deviceAddr << 1, portNum + 0x0C, pullUp); //configure GPPU
- }
-
- /* write() sets pin output to logicLevel (useful for strobePin, one LED pin, or multiple pins).
- pin is bit pattern, where pin being set is 1.
- logicLevel is HIGH or LOW.
- write() does not overwrite the other pins.
- */
- void Port_MCP23S17::write(const uint8_t pin, const bool logicLevel)
- {
- if (logicLevel == LOW)
- {
- outputVal &= ~pin; //set pin output to low
- }
- else
- {
- outputVal |= pin; //set pin output to high
- }
-
- transfer(deviceAddr << 1, portNum + 0x12, outputVal); //set GPIO port to outputVal
- }
-
- /* read() returns portState. Only portState pins with pull resistors are valid.
- */
- uint8_t Port_MCP23S17::read()
- {
- return transfer( (deviceAddr << 1) | 1, portNum + 0x12, 0); //read from GPIO
- }
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