Merge branch 'main' of le-potato

src/main.cpp

@@ -27,6 +27,11 @@
 #define MIDI_NOTE_OFFSET 24
 #define MIDI_NOTE_LENGTH 61
 
+// NOTE: the max output from the MCP4921 DAC is 5.5V, but we have enough DAC
+// 	resolution to use a voltage amplifier with a gain of 2 to extend the range
+// 	to a full 10V. this gives us a range of 121 notes, most of the full MIDI
+// 	range
+#define USE_10V_MAX_CV true
 #define MAX_DAC_INPUT 4095 // 2^12 - 1
 #define TEST_DELAY 5 // seconds to sleep in the test loop
 
@@ -48,11 +53,15 @@ showUsage(const char* prog_name)
 u32
 convertNoteToDACInput(u8 midi_note)
 {
+#if USE_10V_MAX_CV
+	u32 dac = midi_note * 68 / 2;
+#else
 	// NOTE: assuming
 	// 	DAC: 5V = 4080 / 4095 * Vref, Vref ~= 5.0184
 	// 	1 half step/note = 1/12V = dac 68
 	// 	1 octave = 1V = dac 816
 	u32 dac = midi_note * 68;
+#endif
 	(dac > MAX_DAC_INPUT) ? dac = MAX_DAC_INPUT : dac;
 
 	return dac;
@@ -120,12 +129,15 @@ loopMIDI(alsa_sequencer* seq, spi_connection* spi, gpio_info* gpio)
 void
 loopTestVoltages(spi_connection* spi)
 {
-	u32 zero_volts = 0;
-	u32 one_volt = 816;
+	u32 one_volt = 408;
 
 	for (u32 i = 0;; i++) {
-		u32 volts = (i % 2 == 0) ? zero_volts : one_volt;
+#if 0
+		u32 volts = (i % 2 == 0) ? 0 : one_volt;
 		spiSendVoltage(spi, volts);
+#else
+		spiSendVoltage(spi, 10 * one_volt);
+#endif
 		sleep(TEST_DELAY);
 	}
 }