69 lines
2.5 KiB
Arduino
69 lines
2.5 KiB
Arduino
|
/* simulate one scan of a key martix, on source active-low I/O expander
|
||
|
|
|
||
|
|
BREADBOARD SETUP *******************************
|
||
|
|
Teensy LC connected to MCP23017 I/O expander via I2C
|
||
|
|
4.7k Ohm pullup resistors on SDA and SCL
|
||
|
|
use volt meter to measure pin voltages
|
||
|
|
|
||
|
|
MCP23017 PIN DIAGRAM ***************************
|
||
|
|
write port B read port A
|
||
|
|
jumper0 GPB0 1 26 GPA7
|
||
|
|
GPB1 2 25 GPA6
|
||
|
|
GPB2 3 24 GPA5
|
||
|
|
GPB3 4 23 GPA4 jumper4
|
||
|
|
jumper4 GPB4 5 22 GPA3
|
||
|
|
GPB5 6 21 GPA2
|
||
|
|
GPB6 7 20 GPA1
|
||
|
|
GPB7 8 19 GPA0 jumper0
|
||
|
|
power VDD 9 18 INTA
|
||
|
|
GND VSS 10 28 INTB
|
||
|
|
NC 11 27 RESET power
|
||
|
|
SCL SCL 12 17 A2 gnd
|
||
|
|
SDA SDA 13 16 A1 gnd
|
||
|
|
NC 14 15 A0 gnd
|
||
|
|
*/
|
||
|
|
#include "Wire.h"
|
||
|
|
|
||
|
|
const uint8_t ADDR = 0x20; //MCP23017 I2C address with all ADDR pins 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 power (strobe, LED on), pins 4-7 ground
|
||
|
|
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() { }
|