#include <stdio.h>
#include "pico/stdlib.h"
#include "pico/binary_info.h"
#include "hardware/i2c.h"

const int SDA_PIN = 8;
const int SCL_PIN = 9;

// I2C reserves some addresses for special purposes. We exclude these from the scan.
// These are any addresses of the form 000 0xxx or 111 1xxx
bool reserved_addr(uint8_t addr) {
    return (addr & 0x78) == 0 || (addr & 0x78) == 0x78;
}

int main() {
  // Enable UART so we can print status output
  stdio_init_all();
  // This example will use I2C0 on the default SDA and SCL pins (GP4, GP5 on a Pico)
  i2c_init(i2c_default, 100 * 1000);
  gpio_set_function(SDA_PIN, GPIO_FUNC_I2C);
  gpio_set_function(SCL_PIN, GPIO_FUNC_I2C);
  gpio_pull_up(SDA_PIN);
  gpio_pull_up(SCL_PIN);
  // Make the I2C pins available to picotool
  bi_decl(bi_2pins_with_func(SDA_PIN, SCL_PIN, GPIO_FUNC_I2C));

  printf("\nI2C Bus Scan\n");

  for (int addr = 0; addr < (1 << 7); ++addr) {
    // if 1-byte dummy read is possible on the address, 
    //    the function returns the number of bytes available (>0)
    // If the address byte is ignored, the function returns -1

    int ret;
    uint8_t rxdata;

    // Skip over any reserved addresses.
    if (reserved_addr(addr))
        ret = PICO_ERROR_GENERIC;
    else
        ret = i2c_read_blocking(i2c_default, addr, &rxdata, 1, false);

    if (ret > 0 ) printf("00x%x\n", addr);
  }
  printf("Done.\n");
  return 0;
}