scan keyboard

src/key.c

@@ -0,0 +1,62 @@
+/*
+ * key.c
+ *
+ *  Created on: Mar 20, 2019
+ */
+
+#include <stdint.h>
+#include "stc15.h"
+
+
+static uint8_t keys[5];
+
+void KeyInit(void){
+	//set column drivers bits 7:4 to quasi-bidirectional w/ pullup M[1:0]=b00
+	//and row inputs bits 3:0 to quasi-bidirectional w/ pullup M[1:0]=b00
+	P1M1 = 0x00;
+	P1M0 = 0x00;
+	//all initially pulled up
+	P1 = 0xff;
+
+	//read top row input buttons using quasi-bidirectional w/ pullup M[1:0]=b00
+	//P3[1:0]
+	P3M1 &= ~(0x3);
+	P3M0 &= ~(0x3);
+	P3 |= 0x3; //pull up
+	//P5[5:4]
+	P5M1 &= ~(0x30);
+	P5M0 &= ~(0x30);
+	P5 |= 0x30; //pull up
+}
+
+
+void KeyScan(void){
+	//top row not part of matrix
+	static const uint8_t M_ROWS = 4;
+	static const uint8_t M_COLS = 4;
+	uint8_t i, j;
+
+	//scan top row
+	keys[0] = 0; //initially
+	keys[0] += (P3_0 ? 0 : (1<<0)); //on
+	keys[0] += (P3_1 ? 0 : (1<<1));
+	keys[0] += (P5_4 ? 0 : (1<<2));
+	keys[0] += (P5_5 ? 0 : (1<<3));
+	//scan matrix
+	for (i = 0; i < M_ROWS; i++){
+		keys[i+1] = 0; //initially
+		for (j = 0; j < M_COLS; j++){
+			uint8_t read;
+			P1 = (~(1 << (j+4))); //pulldown column (all others pull up)
+			read = (P1 & (1<<i)); //read button
+			read = (read == 0 ? 1 : 0); //pressed if grounded by column driver
+			keys[i+1] += (read << j);
+			P1 = 0xff; //reset all as pullups
+		}
+	}
+}
+
+uint8_t* GetKeys(void){
+	return keys;
+}
+