81 lines
2.6 KiB
C++
81 lines
2.6 KiB
C++
#include "Port_MCP23018.h"
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/* beginProtocol() is called from Scanner_IOE::begin(). Initiates I2C bus.
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MCP23018 supports I2C SCL Clock Frequencies: 100 kHz, 400 kHz, 1000 kHz (Datasheet page 1 & 6)
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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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http://playground.arduino.cc/Main/WireLibraryDetailedReference > Wire.setclock()
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*/
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void Port_MCP23018::beginProtocol()
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{
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Wire.begin(); //initiate I2C bus to 100 kHz
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}
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/* begin() is called from Scanner_IOE::begin().
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Configures port's IODIR and GPPU.
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*/
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void Port_MCP23018::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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Wire.beginTransmission(deviceAddr);
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Wire.write(portNum); //IODIR
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Wire.write(readPins); //0=output (for strobe and LED), 1=input (for read)
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Wire.endTransmission();
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Wire.beginTransmission(deviceAddr);
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Wire.write(portNum + 0x0C); //GPPU
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Wire.write(pullUp);
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Wire.endTransmission();
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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_MCP23018::writeLow(const uint8_t pin)
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{
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outputVal &= ~pin; //set pin output to low
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Wire.beginTransmission(deviceAddr);
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Wire.write(portNum + 0x12); //GPIO
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Wire.write(outputVal);
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Wire.endTransmission();
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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_MCP23018::writeHigh(const uint8_t pin)
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{
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outputVal |= pin; //set pin output to high
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Wire.beginTransmission(deviceAddr);
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Wire.write(portNum + 0x12); //GPIO
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Wire.write(outputVal);
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Wire.endTransmission();
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}
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/* read() returns portState.
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Only portState bits of readPins are valid.
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*/
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uint8_t Port_MCP23018::read()
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{
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Wire.beginTransmission(deviceAddr);
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Wire.write(portNum + 0x12); //GPIO
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Wire.endTransmission(false); //MCP23018 needs false to send a restart ??really?
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Wire.requestFrom(deviceAddr, 1u); //request one byte from input port
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return Wire.read();
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}
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