test adc external connection

src/adc_probe_ext.c

@@ -0,0 +1,39 @@
+#include <avr/io.h>
+#include "adc_probe_ext.h"
+
+void adc_init(void)
+{
+    // Vcc as reference, select ADC2 (MUX = 0b010)
+    ADMUX = (0 << REFS1) | (0 << REFS0) | // VCC as reference
+            (0 << ADLAR) |                // Right adjust result
+            (0b010);                      // ADC2
+
+    // Enable ADC, prescaler = 64 (assuming 8 MHz → ADC freq = 125 kHz)
+    ADCSRA = (1 << ADEN) |                // Enable ADC
+             (1 << ADPS2) | (1 << ADPS1); // Prescaler = 64
+}
+
+uint16_t adc_read(uint8_t channel)
+{
+    // Set channel (0–7), keeping the other bits in ADMUX
+    ADMUX = (ADMUX & 0xF8) | (channel & 0x07);
+
+    ADCSRA |= (1 << ADSC); // Start conversion
+    while (ADCSRA & (1 << ADSC))
+        ; // Wait for conversion to finish
+
+    return ADC; // Return 10-bit result
+}
+
+uint8_t is_device_connected(void)
+{
+    uint16_t value = adc_read(2); // ADC2 = PA2
+
+    // Zakładamy 5V Vcc → 2.5V = około 512
+    if (value > 400 && value < 600)
+    {
+        return 1; // Podłączone (w granicach tolerancji)
+    }
+
+    return 0; // Odłączone (napięcie bliskie 0 lub 5V)
+}