Reverse engineered and wired up R455 timer

misc/reverse_engineered_hardware/r455_timer/r455_timer.ino

@@ -0,0 +1,86 @@
+#include "PCF8575.h"
+
+#define RESET_BUTTON_PIN A3
+#define START_BUTTON_PIN A0
+#define STOP_BUTTON_PIN A2
+#define MODE_SWITCH A1
+
+// These are IO expanders, connected to the LED display
+PCF8575 pcf_0(0x20);
+PCF8575 pcf_1(0x22);
+
+// Goes from 0-9, then a blocky 8, -, then blank
+uint8_t display_value[7] = {11, 11, 11, 11, 11, 11, 11};
+
+// Arduino pins the dials are connected to
+uint8_t dial_pins[6] = {2, 3, 5, 6, 9, 10};
+
+// Values for analogRead() for the dials. Maps dial position to expected value.
+int16_t dial_analog_values[10] = {6, 85, 160, 214, 280, 314, 353, 382, 410, 430};
+
+// warning, the "5"-position is broken on two of the dials and sometimes only retuns some of the bits it's composed of
+uint8_t dial_readout[6] = {0};
+
+void setup()
+{
+  Serial.begin(115200);
+  pcf_0.begin();
+	pcf_1.begin();
+	Serial.print("Connected? : ");
+	Serial.println(pcf_0.isConnected());
+	Serial.println(pcf_1.isConnected());
+	delay(1000);
+	for (int i = 0; i < 6; i++) {
+		pinMode(dial_pins[i], OUTPUT);
+		digitalWrite(dial_pins[i], LOW);
+	}
+	pinMode(RESET_BUTTON_PIN, INPUT_PULLUP);
+	pinMode(STOP_BUTTON_PIN, INPUT_PULLUP);
+	pinMode(START_BUTTON_PIN, INPUT_PULLUP);
+	pinMode(MODE_SWITCH, INPUT_PULLUP);
+}
+
+void updateDisplay() {
+	uint8_t shift_to_pin[4] = {2, 0, 1, 3};
+	for (uint8_t display = 0; display < 7; display++) {
+		for (uint8_t shift = 0; shift < 4; shift++) {
+			uint8_t pin = shift_to_pin[shift];
+			if (display >= 4) {
+				pcf_1.write((display - 4) * 4 + pin, 0 < (display_value[display] & (1 << shift)));
+			} else {
+				pcf_0.write(display * 4 + pin, 0 < (display_value[display] & (1 << shift)));
+			}
+		}
+	}
+}
+
+void readDial() {
+	// Reads all dials by turning on dial pins one by one, then measuring the
+	//  voltage in the resistor network
+	for (int dial = 0; dial < 6; dial++) {
+		digitalWrite(dial_pins[dial], HIGH);
+		delay(1);
+		int16_t measured = analogRead(A7);
+		digitalWrite(dial_pins[dial], LOW);
+		int16_t minimal_difference = 1024;
+		uint8_t best_candidate = 0;
+		for (uint8_t i = 0; i < 10; i++) {
+			int16_t difference = abs(measured - dial_analog_values[i]);
+			if (difference < minimal_difference) {
+				minimal_difference = difference;
+				best_candidate = i;
+			}
+		}
+		dial_readout[dial] = best_candidate;
+	}
+}
+
+
+void loop()
+{
+	readDial();
+	for (int i = 0; i < 6; i++) {
+		display_value[6 - i] = dial_readout[i];
+	}
+	updateDisplay();
+}