ao-bringup-avr: Make LED PWM from ADC0 value

Test ADC inputs by adjusting the waveform using the ADC0 input.

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

diff --git a/ao-bringup-avr/ao-blink.c b/ao-bringup-avr/ao-blink.c
index fa95831529bb84a4ce5dd31ddfb8ba89c40951f2..e41bc91834b5af4d7b258f86ff140880987688ea 100644 (file)
--- a/ao-bringup-avr/ao-blink.c
+++ b/ao-bringup-avr/ao-blink.c
@@ -17,7 +17,12 @@
 
 #include <avr/io.h>
 #include <avr/interrupt.h>
+#define TEENSY 1
+#if TEENSY
 #define F_CPU 16000000UL       // 16 MHz
+#else
+#define F_CPU  8000000UL       // 8 MHz
+#endif
 #include <util/delay.h>
 
 #define LEDOUT         PORTB7
@@ -25,18 +30,16 @@
 #define LEDDDR         DDRB
 #define LEDDDRPIN      DD7
 
+static void
+adc_start(void);
+
 ISR(TIMER1_COMPA_vect)
 {
-       static int      x;
-
-       if (++x > 50) {
-               x = 0;
-               LEDPORT ^= (1 << LEDOUT);
-       }
+       adc_start();
 }
 
 static void
-timer_init(void)
+timer1_init(void)
 {
        TCCR1A = ((0 << WGM11) |        /* CTC mode, OCR1A */
                  (0 << WGM10));        /* CTC mode, OCR1A */
@@ -46,8 +49,11 @@ timer_init(void)
                  (1 << WGM12) |        /* CTC mode, OCR1A */
                  (3 << CS10));         /* clk/64 from prescaler */
 
+#if TEENSY
        OCR1A = 2500;                   /* 16MHz clock */
-       // OCR1A = 1250;                /* 8MHz clock */
+#else
+       OCR1A = 1250;                   /* 8MHz clock */
+#endif
 
        TIMSK1 = (1 << OCIE1A);         /* Interrupt on compare match */
 }
@@ -86,8 +92,11 @@ clock_init(void)
                  (0x4 << PDIV0));      /* 48MHz PLL clock */
 
        /* Set the frequency of the crystal */
+#if TEENSY
        PLLCSR |= (1 << PINDIV);        /* For 16MHz crystal on Teensy board */
-       // PLLCSR &= ~(1 << PINDIV);    /* For 8MHz crystal on TeleScience board */
+#else
+       PLLCSR &= ~(1 << PINDIV);       /* For 8MHz crystal on TeleScience board */
+#endif
 
        /* Enable the PLL */
        PLLCSR |= (1 << PLLE);
@@ -95,21 +104,66 @@ clock_init(void)
                ;
 }
 
+static void
+timer0_init(void)
+{
+       TCCR0A = ((1 << COM0A1) |
+                 (0 << COM0A0) |
+                 (1 << WGM01) |
+                 (1 << WGM00));
+
+       OCR0A = 0x10;
+       OCR0B = 0;
+       TIMSK0 = 0;
+
+       TCCR0B = ((0 << WGM02) |
+                 (5 << CS00));
+}
+
+ISR(ADC_vect)
+{
+       OCR0A = ADCH;
+}
+
+static void
+adc_start(void)
+{
+       ADMUX = ((0 << REFS1) |
+                (1 << REFS0) |
+                (1 << ADLAR) |
+                (0 << MUX0));
+       ADCSRB &= ~(1 << MUX5);
+
+       ADCSRA = ((1 << ADEN) |
+                 (1 << ADSC) |
+                 (0 << ADATE) |
+                 (1 << ADIE) |
+                 (6 << ADPS0));
+}
+
+static void
+adc_init(void)
+{
+       ADCSRA = ((1 << ADEN) |
+                 (0 << ADSC) |
+                 (0 << ADATE) |
+                 (1 << ADIE) |
+                 (6 << ADPS0));
+       ADCSRB = ((0 << ADHSM) |
+                 (0 << MUX5) |
+                 (0 << ADTS0));
+       DIDR0 |= (1 << 0);
+}
+
 int main(void)
 {
        clock_init();
-       timer_init();
+       adc_init();
+       timer1_init();
+       timer0_init();
 
        LEDDDR |= (1 << LEDDDRPIN);
 
-       for (;;) {
-       }
-#if 0
-       while (1) {
-               LEDPORT |= (1 << LEDOUT);
-               _delay_ms(1000);
-               LEDPORT &= ~(1 << LEDOUT);
-               _delay_ms(1000);
-       }
-#endif
+       for (;;)
+               ;
 }