From: Michel Pollet <buserror@gmail.com>
Date: Wed, 14 Apr 2010 17:15:23 +0000 (+0100)
Subject: test: Add a test/example for the ADC subsystem
X-Git-Url: http://git.rot13.org/?a=commitdiff_plain;h=6b34bedf4f80f155bee3c3a2fe7b542ee875fbc1;p=simavr

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
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();
+
+}
+