adc+rand

include/adc.c

@@ -10,9 +10,9 @@ void adc_init() {
 	ADMUX = (1<<REFS0);
 }
 uint16_t adc_read(uint8_t channel) {
-    ADMUX &= 0xf0;
-    ADMUX |= (channel & 0x0f);
-    ADCSRA |= (1<<ADSC);
-    while((ADCSRA&(1<<ADIF))==0);
-    return ADCL + (ADCH << 8);
+    ADMUX &= 0xf0; // max channel?
+    ADMUX |= (channel & 0x0f); // select channel
+    ADCSRA |= (1<<ADSC); // interrupt enable
+    while((ADCSRA&(1<<ADIF))==0); // wait for something
+    return ADCL + (ADCH << 8); // read
 }

include/rand.c

@@ -1,5 +1,7 @@
+#include "adc.h"
 int rand() {
     static unsigned int seed = 1337191337;
+    seed *= adc_read(3);
     unsigned int buf[] = {
         (seed*31832)%677,
         (seed*32932)%2332

print/main.c

@@ -17,7 +17,6 @@ int main (void)
     adc_init();
     sei();
 
-    char buf[10];
     uint16_t sensor[2] = { 0, 1 };
 
     while (1)
@@ -28,6 +27,8 @@ int main (void)
         // we want to print this, so we store the ascii repr in our buffer
         uart_printi("sensor 0: ", sensor[0]);
         uart_printi("sensor 1: ", sensor[1]);
+        uart_printi("sensor 2 (noise): ", adc_read(2));
+        uart_printi("rand: ", rand());
         _delay_ms(1000);
     }
 }