1 files changed, 53 insertions, 0 deletions
diff --git a/keyboard/preonic/analog.c b/keyboard/preonic/analog.c
new file mode 100644
index 000000000..49b84ee0e
--- /dev/null
+++ b/keyboard/preonic/analog.c
@@ -0,0 +1,53 @@
+// Simple analog to digitial conversion
+
+#include <avr/io.h>
+#include <avr/pgmspace.h>
+#include <stdint.h>
+#include "analog.h"
+
+
+static uint8_t aref = (1<<REFS0); // default to AREF = Vcc
+
+
+void analogReference(uint8_t mode)
+{
+	aref = mode & 0xC0;
+}
+
+
+// Arduino compatible pin input
+int16_t analogRead(uint8_t pin)
+{
+#if defined(__AVR_ATmega32U4__)
+	static const uint8_t PROGMEM pin_to_mux[] = {
+		0x00, 0x01, 0x04, 0x05, 0x06, 0x07,
+		0x25, 0x24, 0x23, 0x22, 0x21, 0x20};
+	if (pin >= 12) return 0;
+	return adc_read(pgm_read_byte(pin_to_mux + pin));
+#elif defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB1286__)
+	if (pin >= 8) return 0;
+	return adc_read(pin);
+#else
+	return 0;
+#endif
+}
+
+// Mux input
+int16_t adc_read(uint8_t mux)
+{
+#if defined(__AVR_AT90USB162__)
+	return 0;
+#else
+	uint8_t low;
+
+	ADCSRA = (1<<ADEN) | ADC_PRESCALER;		// enable ADC
+	ADCSRB = (1<<ADHSM) | (mux & 0x20);		// high speed mode
+	ADMUX = aref | (mux & 0x1F);			// configure mux input
+	ADCSRA = (1<<ADEN) | ADC_PRESCALER | (1<<ADSC);	// start the conversion
+	while (ADCSRA & (1<<ADSC)) ;			// wait for result
+	low = ADCL;					// must read LSB first
+	return (ADCH << 8) | low;			// must read MSB only once!
+#endif
+}
+
+