Debugging and Testing Embedded Code

See what the device is really doing

Serial logging is the first tool: print state changes and key values with timestamps, behind a debug flag so you can turn it off. Remember printing takes time and can change timing-sensitive behaviour. A multimeter checks voltages and continuity; a logic analyser captures digital signals over time and can decode UART, I2C and SPI, which is invaluable when a bus misbehaves; an oscilloscope shows analog detail such as noise or slow edges. Some boards support hardware debuggers with breakpoints. For correctness, separate pure logic (parsing, filtering, state transitions, unit conversions) from hardware access so it can be compiled and unit-tested on your PC with a normal compiler; test hardware-touching code on the device. Tools such as PlatformIO include unit-test runners; check their docs.

Logic separated from hardware, tested on the host

Plain C: the conversion function has no hardware dependencies, so it compiles both for the board and for a PC test program.

/* temp.h / temp.c: pure logic, shared by firmware and tests */
#include <stdint.h>

/* TMP36 on a 10-bit, 5 V ADC: returns tenths of a degree C */
int16_t tmp36_tenths_c(uint16_t raw) {
    int32_t millivolts = (int32_t)raw * 5000 / 1023;
    return (int16_t)(millivolts - 500);   /* 10 mV per degC = 1 mV per 0.1 degC */
}

/* test_temp.c: built with a desktop compiler, not uploaded */
#include <assert.h>
int main(void) {
    assert(tmp36_tenths_c(0) == -500);    /* 0 V    -> -50.0 C */
    assert(tmp36_tenths_c(153) == 247);   /* ~0.748 V -> about 24.7 C */
    return 0;
}

Compile and run the host test

Shown, not run; any desktop C compiler works.

gcc -Wall -Wextra -o test_temp test_temp.c temp.c
./test_temp && echo "all tests passed"

Debug macros that compile away

Wrap logging in a macro such as DEBUG_PRINT that expands to nothing when a DEBUG flag is off, so release builds pay no flash, RAM or timing cost.

त्वरित जाँच: Which tool is best for seeing why an I2C transaction fails?

• A thermometer on the chip
• Adding a longer delay() at random places
• A logic analyser that captures and decodes SDA and SCL
• Recompiling with a different baud rate