m05e01 done

module05/ex01/adc.c

@@ -1,25 +1,34 @@
 #include "header.h"
 
-// Table 14-6. Port C Pins Alternate Functions
-// - PC0 -> ADC0 (ADC Input Channel 0)
-//       -> PCINT8 (Pin Change Interrupt 8)
-//
 // 24.2 : The ADC generates a 10-bit result which is presented in the ADC Data Registers, ADCH and ADCL
-//
-// START A CONVERSTION in single conversion mode :
-// - disabling the Power Reduction ADC bit, PRADC
-// - writing a logical one to the ADC Start Conversion bit, ADSC
 
 void adc_init(uint8_t prescaler_value) {
-    ADMUX = (1 << REFS0);								// Table 24-3 : set voltage reference, AVCC with external capacitor at AREF pin
+    ADMUX = (1 << REFS0);									// Table 24-3 : set voltage reference, AVCC with external capacitor at AREF pin
-    ADCSRA = (1 << ADEN); 								// 24.9.2 : enable ADC
+    ADCSRA = (1 << ADEN); 									// 24.9.2 : enable ADC
-    ADCSRA |= ADC_PRESCALE_SET(prescaler_value);		// Table 24-5 : prescaler ADC
+	ADCSRA |= (1 << ADATE); 								// 24.9.2 : enable Auto Trigger -> it will start a conversion on the selected channel in ADMUX when the selected source (in ADCSRB) is triggered
+	ADCSRA |= (1 << ADIE);								 	// 24.9.2 : enable ADC Interrupt
+    ADCSRA |= ADC_PRESCALE_SET(prescaler_value);			// Table 24-5 : prescaler ADC
+
+	ADCSRB = ADC_TRIGGER_TIMER_1_COMPARE_B;					// Table 24-6 : ADC Auto Trigger Source
+	ADMUX = (ADMUX & 0b11110000) | (adc_channel & 0b1111);	// Table 24-4 : Select ADC channel 0
 }
 
-uint16_t adc_read(uint8_t channel) {
+
-	CLEAR(PRR, PRADC);									// 24.3 : ensure power reduction is disabled for ADC, (10.11.3 : PRR – Power Reduction Register)
+void adc_print_hex(uint8_t value) {
-    ADMUX = (ADMUX & 0b11110000) | (channel & 0b1111);	// Table 24-4 : Select ADC channel, (Table 14-6 : alternate function for RV1 on PC0 -> ADC0)
+	char buffer[3] = {0};
-    ADCSRA |= (1 << ADSC);								// 24.9.2 : Start conversion, ADSC: ADC Start Conversion
+	int_to_hex_string(value, buffer, 2);
-    while (ADCSRA & (1 << ADSC));						// Wait for completion
+	uart_printstr(buffer);
-    return ADC;
+}
+
+ISR(ADC_vect) {												// Table 12-6 : interrupt vector for ADC Conversion Complete
+	uint16_t value = ADC;
+	adc_print_hex(value);
+	adc_channel = (adc_channel + 1) % 3;					// loop through channels
+	ADMUX = (ADMUX & 0b11110000) | (adc_channel & 0b1111);	// Table 24-4 : Select ADC channel
+	if (adc_channel != 0) {
+		uart_printstr(", ");
+		ADCSRA |= (1 << ADSC);								// 24.9.2 : start next conversion
+	} else {
+		uart_printstr("\r\n");
+	}
 }

module05/ex01/header.h

@@ -16,6 +16,9 @@
 // PROTOTYPES
 //
 // main.c
+// timer.c
+void timer_1B_init();
+// math.c
 void int_to_hex_string(uint64_t value, char *out, uint8_t num_digits);
 // adc.c
 void adc_init(uint8_t prescaler_value);

module05/ex01/main.c

@@ -2,31 +2,28 @@
 
 // 1.1.7 : AVCC is the supply voltage pin for the A/D Converter, PC3:0, and ADC7:6
 // 1.1.8 : AREF is the analog reference pin for the A/D Converter
+// 24.4 : frequency needs to be between 50kHz and 200kHz, for less than 10bits accuracy it can be >200kHz
+//  -> Frequence_ADC = Frequance_CPU / Prescaler (Fadc = Fcpu/P):
+//     - P = 2   -> Fadc = 16,000,000 / 2   = 8,000,000 = 8MHz
+//     - P = 4   -> Fadc = 16,000,000 / 4   = 4,000,000 = 4MHz
+//     - P = 8   -> Fadc = 16,000,000 / 8   = 2,000,000 = 2MHz
+//     - P = 16  -> Fadc = 16,000,000 / 16  = 1,000,000 = 1MHz
+//     - P = 32  -> Fadc = 16,000,000 / 32  =   500,000 = 500KHz
+//     - P = 64  -> Fadc = 16,000,000 / 64  =   250,000 = 250KHz -> OK
+//     - P = 128 -> Fadc = 16,000,000 / 128 =   125,000 = 125KHz -> OK
 
-#define ADC_PRESCALER	8
+#define ADC_PRESCALER	64						// Table 24-5 : can only be 2, 4, 8, 16, 32, 64, or 128
 
-void int_to_hex_string(uint64_t value, char *out, uint8_t num_digits) {				// num_digits : number of digit of the output, ex 2 for 3FF (1023) -> FF
+volatile uint8_t adc_channel = 0;				// Table 14-6 : alternate function for RV1 on PC0 -> ADC0, LDR on PC1 -> ADC1, NTC on PC2 -> ADC2 ...
-    for (uint8_t i = 0; i < num_digits; ++i) {
-        uint8_t shift = (num_digits - 1 - i) * 4;
-        out[i] = INT_TO_HEX_CHAR((value >> shift) & 0x0F);
-    }
-    out[num_digits] = '\0';
-}
 
-// description
+// read 3 analog values and print them in uart as hexadecimal 2-number : potentiometer RV1 (Variable Resistor), photoresistor LDR (Light Dependent Resistor), thermistor NTC (Negative Temperature Coefficient)
 int main() {
     char buffer[4];
-	SREG |= ENABLE_GLOBAL_INTERRUPT;												// 7.3.1 : Status Register, bit 7 : I – Global Interrupt Enable
+	SREG |= ENABLE_GLOBAL_INTERRUPT;			// 7.3.1 : Status Register, bit 7 : I – Global Interrupt Enable
 	uart_init();
 	adc_init(ADC_PRESCALER);
 
-	while(1) {
+	timer_1B_init();
-        uint16_t value = adc_read(0);												// Read from ADC0 (A0)
-		int_to_hex_string(value, buffer, 3);
-        uart_printstr_endl(buffer);
-        _delay_ms(20);																// Wait 20ms
-	}
-}
 
-// ISR(ADC_vect) {		// Table 12-6 : interrupt vector for ADC Conversion Complete
+	while(1);
-// }
+}

module05/ex01/timer.c

@@ -0,0 +1,22 @@
+#include "header.h"
+
+// Set up Timer1 in CTC mode to trigger every 20ms
+// With 16MHz clock and prescaler of 64, and OCR1A = 49999:
+// 16000000/64/50000 = 20ms period
+
+#define T1B_PRESCALE_VALUE	64
+
+void timer_1B_init() {
+	TCCR1A = 0;											// 16.11.1 : Normal operation, OC1A/OC1B disconnected
+	TCCR1B = CTC_TOP_OCR1A_IN_TCCR1B;					// 16.11.2 : CTC mode top OCR1A
+	TCCR1B |= T1_PRESCALE_SET(T1B_PRESCALE_VALUE);		// 16.11.2 : prescaler
+
+	OCR1A = TIME_MS(20, T1B_PRESCALE_VALUE);			// 16.11.5 : Compare match value for register A
+	OCR1B = 0;											// 16.11.6 : Compare match value for register B, if not defined, should default to 0
+
+	TIMSK1 = (1 << OCIE1B);								// 16.11.8 : Enable Timer1 Compare B Match Interrupt
+}
+
+ISR(TIMER1_COMPB_vect) {
+    // Empty ISR to ensure proper flag clearing or something like that (p145 : "OCF1B is automatically cleared when the Output Compare Match B Interrupt Vector is executed")
+}