123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869 |
- /* simulate one scan of a key martix, on open-drain active-low I/O expander
-
- BREADBOARD SETUP *******************************
- Teensy LC connected to MCP23018 I/O expander via I2C
- 4.7k Ohm pullup resistors on SDA and SCL
- use volt meter to measure pin voltages
- MCP23018 has open-drain outputs (open-drain can only sink current)
-
- MCP23018 PIN DIAGRAM ***************************
- write port B read port A
- GND VSS 1 28 NC
- NC 2 27 GPA7
- jumper0 GPB0 3 26 GPA6
- GPB1 4 25 GPA5
- GPB2 5 24 GPA4 jumper4
- GPB3 6 23 GPA3
- jumper4 GPB4 7 22 GPA2
- GPB5 8 21 GPA1
- GPB6 9 20 GPA0 jumper0
- GPB7 10 19 INTA
- power VDD 11 18 INTB
- SCL SCL 12 17 NC
- SDA SDA 13 16 RESET power
- NC 14 15 ADDR GND
- */
- #include "Wire.h"
-
- const uint8_t ADDR = 0x20; //MCP23018 I2C address with ADDR pin grounded
-
- void setup()
- {
- delay(1000); //time for Serial print to work
-
- // ================= configure ================
- Serial.print("config ");
- Wire.begin();
-
- Wire.beginTransmission(ADDR);
- Wire.write(0x01); //IODIRB Configure
- Wire.write(0); //as output
- Wire.endTransmission();
-
- Wire.beginTransmission(ADDR);
- Wire.write(0x00); //IODIRA Configuration
- Wire.write(~0); //as input
- Wire.endTransmission();
-
- Wire.beginTransmission(ADDR);
- Wire.write(0x0C); //GPPUA pull-up
- Wire.write(~0); //pull-up enabled
- Wire.endTransmission();
-
- // =================== scan ===================
- Serial.println("scan");
-
- Wire.beginTransmission(ADDR);
- Wire.write(0x13); //GPIOB output
- Wire.write(B00001111); //pins 0-3 off, pins 4-7 sink on (strobe, LED on)
- Wire.endTransmission();
-
- Wire.beginTransmission(ADDR);
- Wire.write(0x12); //GPIOA (immediately before requestFrom)
- Wire.endTransmission();
-
- Wire.requestFrom(ADDR, static_cast<uint8_t>(1)); //request one byte from GPIOA read
- Serial.print("portA=");
- Serial.println(Wire.read(), BIN); //prints portA=11101111
- }
- void loop() { }
|