test: Add a test/example for the ADC subsystem

Loads ADC values, also reads the V1.1 reference voltage of an Atmega644

Signed-off-by: Michel Pollet <buserror@gmail.com>

diff --git a/tests/atmega644_adc_test.c b/tests/atmega644_adc_test.c
new file mode 100644 (file)
index 0000000..0a0c2b3
--- /dev/null
+++ b/tests/atmega644_adc_test.c
@@ -0,0 +1,106 @@
+/*
+       atmega644_adc_test.c
+
+       Copyright 2008, 2009 Michel Pollet <buserror@gmail.com>
+
+       This file is part of simavr.
+
+       simavr 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 3 of the License, or
+       (at your option) any later version.
+
+       simavr 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.
+
+       You should have received a copy of the GNU General Public License
+       along with simavr.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <avr/io.h>
+#include <stdio.h>
+#include <avr/interrupt.h>
+#include <avr/delay.h>
+#include <avr/sleep.h>
+
+/*
+ * This demonstrate how to use the avr_mcu_section.h file
+ * The macro adds a section to the ELF file with useful
+ * information for the simulator
+ */
+#include "avr_mcu_section.h"
+AVR_MCU(F_CPU, "atmega644");
+AVR_MCU_VOLTAGES(3300, 3300, 3300);    // 3.3V VCC, AVCC, VREF
+
+static int uart_putchar(char c, FILE *stream) {
+  if (c == '\n')
+    uart_putchar('\r', stream);
+  loop_until_bit_is_set(UCSR0A, UDRE0);
+  UDR0 = c;
+  return 0;
+}
+
+static FILE mystdout = FDEV_SETUP_STREAM(uart_putchar, NULL,
+                                         _FDEV_SETUP_WRITE);
+
+volatile uint16_t adc_val[8];
+
+ISR(ADC_vect)
+{
+       uint8_t mux = ADMUX, l = ADCL, h = ADCH;
+       uint8_t i = mux & 7;
+       adc_val[i] = l | (h << 8);
+       i = (i + 1) & 7;
+       ADMUX = (mux & 0xF0) | i;
+       if (i)
+               ADCSRA |= (1 << ADSC);          // restart one now on the new channel
+}
+
+void adc_init()
+{
+       // set ADC
+       ADMUX = (1 << REFS0);   // use internal AVCC (3.3)
+       // enable ADC, start a conversion, with the interrupt
+       // and with a /128 integration clock
+       ADCSRA = (1 << ADEN) | (1 << ADSC) | (1 << ADIE) | 0x5;
+       // doesn't do anything in simavr for now
+       DIDR0 = 3;      // disable digital on these 2 pins ADC0 and ADC1
+}
+
+int main(void)
+{
+       stdout = &mystdout;
+
+       sei();
+       printf("Read 8 ADC channels to test interrupts\n");
+
+       adc_init();
+
+       /*
+        * The interupt reads all 8 ADCs then stop...
+        * so this loop will eventually exits
+        */
+       while (ADCSRA & (1 << ADSC))
+               sleep_cpu();
+
+       printf("All done. Now reading the 1.1V value in pooling mode\n");
+       ADCSRA &= ~(1 << ADIE); // remove interrupt
+
+       // 1.1 reference voltage, left aligned
+       ADMUX = (ADMUX & ~0x1f)| (1 << ADLAR) | 0x1e;
+       ADCSRA |= (1 << ADSC) ; // start conversion
+       while (ADCSRA & (1 << ADSC))
+               ;
+       uint16_t v = ADCL | (ADCH << 8);
+       uint16_t volts = (v * 3300L) >> 10; // div 1024
+       printf("Read ADC value %04x = %d mvolts -- ought to be 1098\n", v, volts);
+
+       ADCSRA &= ~(1 << ADEN); // disable ADC...
+
+       cli();
+       sleep_cpu();
+
+}
+