tinyTemp

tinyTemp started as an ATmega328P prototype so the sensor, OLED display, and temperature conversion flow could be validated quickly. After the core behavior worked, the design was iterated onto an ATtiny85 for a smaller final PCB and tighter embedded constraints. The finished firmware reads temperature from an analog sensor on ADC channel 2 (1.1 V ref), averages 25 samples, converts to °C and °F, and displays on a 0.96" 128×64 SSD1306 OLED. Display alternates °F (3 s) and °C (3 s) and shows "TOO HOT!!!" above 70 °F. ECE 304 project; all logic on the MCU, no host PC. I2C to the OLED is bit-banged (ATtiny85 has no hardware I2C). Demonstrates embedded C: ADC, timing, PROGMEM, bit-banged I2C, PCB-level iteration, and display driver integration on a resource-constrained MCU.

main() and ADC main() disables the watchdog, then calls adc_init(), OLED_init(), and OLED_clear(). The ADC uses internal 1.1 V ref and channel 2; 25 samples are summed via get_adc() (start conversion, wait for ADIF, read ADCL then ADCH for 10-bit value). Temperature is computed from the averaged reading with a linear formula to °C and then °F.

display_temp and main loop display_temp(value, unit) formats the value to one decimal and prints either " Deg C " or " Deg F " from PROGMEM. The main loop shows °F, and if above 70 °F prints "TOO HOT!!!" at a fixed position; waits 3 s; clears; shows °C with the same logic; then enables the watchdog (8 s) and spins in while(1).

tinyOLED.c driver SSD1306 driver: PROGMEM init sequence (multiplex, addressing, charge pump, display on), 5×8 font, and OLED_cursor / OLED_printC / OLED_printP for positioning and text. Bit-banged I2C on GPIO. Build: make for tinyTemp.c + tinyOLED.c; make flash uses avrdude and USBtinyISP to program the ATtiny85.