altos/attiny: Add ADC implementation

It's primitive, but might serve to read ADC values. Untested.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/src/attiny/ao_adc_attiny.c b/src/attiny/ao_adc_attiny.c
new file mode 100644 (file)
index 0000000..3a835d1
--- /dev/null
+++ b/src/attiny/ao_adc_attiny.c
@@ -0,0 +1,48 @@
+/*
+ * Copyright © 2017 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include <ao.h>
+
+/*
+ * ATtiny ADC interface
+ */
+
+uint16_t
+ao_adc_read(uint8_t mux)
+{
+       uint8_t low, high;
+
+       /* Set the mux */
+       ADMUX = mux;
+
+       /* Start conversion */
+       ADCSRA = ((1 << ADEN) |
+                 (1 << ADSC) |
+                 (0 << ADATE) |
+                 (0 << ADIF) |
+                 (0 << ADIE) |
+                 (0 << ADPS2) |
+                 (0 << ADPS1) |
+                 (0 << ADPS0));
+
+       /* Await conversion complete */
+       while ((ADCSRA & (1 << ADSC)) != 0)
+               ;
+
+       /* Read low first */
+       low = ADCL;
+       high = ADCH;
+
+       return (((uint16_t) high) << 8) | low;
+}

diff --git a/src/attiny/ao_arch.h b/src/attiny/ao_arch.h
index 3a34f417c9cf844099b37ef7a4d528e03f233042..68f5702d78e104293bf0b853b91dcf383f768035 100644 (file)
--- a/src/attiny/ao_arch.h
+++ b/src/attiny/ao_arch.h
@@ -85,4 +85,7 @@ ao_eeprom_read(uint16_t addr, void *buf, uint16_t len);
 void
 ao_eeprom_write(uint16_t addr, void *buf, uint16_t len);
 
 void
 ao_eeprom_write(uint16_t addr, void *buf, uint16_t len);
 

+uint16_t
+ao_adc_read(uint8_t mux);
+

 #endif /* _AO_ARCH_H_ */
 #endif /* _AO_ARCH_H_ */