79 satır
2.9 KiB
C++
79 satır
2.9 KiB
C++
#include "Port_MCP23S17.h"
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/* transfer() writes data to registerAddr, reads portSate from registerAddr, and returns portState.
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MCP23S17 SPI interface is 10 MHz max.
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The electrical limitation to bus speed is bus capacitance and the length of the wires involved.
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Longer wires require lower clock speeds.
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*/
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uint8_t Port_MCP23S17::transfer(const uint8_t command, const uint8_t registerAddr,
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const uint8_t data)
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{
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uint8_t portState; //bit pattern
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SPI.beginTransaction( SPISettings(5000000, MSBFIRST, SPI_MODE0) ); //control SPI bus, 5 MHz
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digitalWrite(slaveSelect, LOW); //enable Slave Select
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SPI.transfer(command); //write or read command
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SPI.transfer(registerAddr); //register address to write data to
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portState = SPI.transfer(data); //write data, read portState
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digitalWrite(slaveSelect, HIGH); //disable Slave Select
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SPI.endTransaction();
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return portState;
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}
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/* beginProtocol() is called from Scanner_IOE::begin(). Initiates SPI bus.
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*/
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void Port_MCP23S17::beginProtocol()
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{
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pinMode(slaveSelect, OUTPUT); //configure controller's Slave Select pin to output
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digitalWrite(slaveSelect, HIGH); //disable Slave Select
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SPI.begin();
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}
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/* begin() is called from Scanner_IOE::begin().
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activeState is logic level of strobe on, HIGH or LOW
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configure IODIR and GPPU.
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*/
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void Port_MCP23S17::begin(const uint8_t activeState)
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{
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uint8_t pullUp; //bits, GPPU 0=pull-up disabled, 1=pull-up enabled
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if (activeState == LOW) //if active low
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{
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pullUp = readPins; //0=pull-up disabled (for LED), 1=pull-up enabled (for read)
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}
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else //if active high
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{
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pullUp = 0; //0=pull-up disabled (for external pull-down resistors)
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}
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transfer(deviceAddr << 1, portNum, readPins); //configure IODIR
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transfer(deviceAddr << 1, portNum + 0x0C, pullUp); //configure GPPU
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}
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/* writeLow() sets pin output LOW.
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pin is bit pattern, where pin being set is 1.
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*/
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void Port_MCP23S17::writeLow(const uint8_t pin)
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{
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outputVal &= ~pin; //set pin output to low
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transfer(deviceAddr << 1, portNum + 0x12, outputVal); //set GPIO port to outputVal
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}
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/* writeHigh() sets pin output HIGH.
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pin is bit pattern, where pin being set is 1.
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*/
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void Port_MCP23S17::writeHigh(const uint8_t pin)
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{
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outputVal |= pin; //set pin output to high
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transfer(deviceAddr << 1, portNum + 0x12, outputVal); //set GPIO port to outputVal
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}
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/* read() returns portState. Only portState pins with pull resistors are valid.
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*/
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uint8_t Port_MCP23S17::read()
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{
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return transfer( (deviceAddr << 1) | 1, portNum + 0x12, 0); //read from GPIO
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}
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