70 lines
2.6 KiB
Arduino
70 lines
2.6 KiB
Arduino
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/* simulate one scan of a key martix, on source active-high I/O expander
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BREADBOARD SETUP *******************************
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Teensy LC connected to MCP23017 I/O expander via I2C
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10k Ohm external pulldown resistors on port A
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4.7k Ohm pullup resistors on SDA and SCL
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use volt meter to measure pin voltages
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MCP23017 PIN DIAGRAM ***************************
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write port B read port A
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jumper0 GPB0 1 26 GPA7 pulldown
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GPB1 2 25 GPA6 pulldown
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GPB2 3 24 GPA5 pulldown
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GPB3 4 23 GPA4 pulldown jumper4
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jumper4 GPB4 5 22 GPA3 pulldown
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GPB5 6 21 GPA2 pulldown
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GPB6 7 20 GPA1 pulldown
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GPB7 8 19 GPA0 pulldown jumper0
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power VDD 9 18 INTA
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GND VSS 10 28 INTB
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NC 11 27 RESET power
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SCL SCL 12 17 A2 gnd
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SDA SDA 13 16 A1 gnd
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NC 14 15 A0 gnd
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*/
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#include "Wire.h"
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const uint8_t ADDR = 0x20; //MCP23017 I2C address with all ADDR pins grounded
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void setup()
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{
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delay(1000); //time for Serial print to work
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// ================= configure ================
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Serial.print("config ");
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Wire.begin();
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Wire.beginTransmission(ADDR);
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Wire.write(0x01); //IODIRB Configure
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Wire.write(0); //as output
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Wire.endTransmission();
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Wire.beginTransmission(ADDR);
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Wire.write(0x00); //IODIRA Configuration
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Wire.write(~0); //as input
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Wire.endTransmission();
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Wire.beginTransmission(ADDR);
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Wire.write(0x0C); //GPPUA pull-up
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Wire.write(0); //pull-up disabled
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Wire.endTransmission();
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// =================== scan ===================
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Serial.println("scan");
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Wire.beginTransmission(ADDR);
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Wire.write(0x13); //GPIOB output
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Wire.write(B11110000); //pins 0-3 ground, pins 4-7 power (strobe, LED on)
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Wire.endTransmission();
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Wire.beginTransmission(ADDR);
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Wire.write(0x12); //GPIOA (immediately before requestFrom)
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Wire.endTransmission();
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Wire.requestFrom(ADDR, static_cast<uint8_t>(1)); //request one byte from GPIOA read
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Serial.print("portA=");
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Serial.println(Wire.read(), BIN); //prints portA=00010000
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}
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void loop() { }
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