balcony_weather_station/pms5003.c

#include "pms5003.h"
#include "hardware/uart.h"
#include "pico/stdlib.h"
#include <hardware/gpio.h>
#include <hardware/regs/intctrl.h>
#include <stdint.h>
#include <stdio.h>
#include <hardware/watchdog.h>

/**
Lib for Plantower PMS5003 Particulate Matter (PM) Sensor

Detects PM1, PM2.5, PM10 particulates

Sourcces:
    -
https://shop.pimoroni.com/products/pms5003-particulate-matter-sensor-with-cable
    - https://github.com/pimoroni/pms5003-python/blob/main/pms5003/__init__.py
    - https://github.com/vogelrh/pms5003c/tree/master
    -
https://github.com/raspberrypi/pico-examples/blob/master/uart/hello_uart/hello_uart.c
*/

#define MAX_READINGS 100

static bool read = false;
static uint16_t reading_i = 0;
static pms5003_reading readings[MAX_READINGS];

static uint8_t rx_buf[32] = {0};
static uint8_t rx_i = 0;

static pms5003_reading extract_pm_values_from_rx_buf() {
  uint8_t pm1_low = rx_buf[9];
  uint8_t pm1_high = rx_buf[10];
  uint16_t pm1 = ((uint16_t)pm1_high << 8) | pm1_low;

  uint8_t pm2_5_low = rx_buf[11];
  uint8_t pm2_5_high = rx_buf[12];
  uint16_t pm2_5 = ((uint16_t)pm2_5_high << 8) | pm2_5_low;

  uint8_t pm10_low = rx_buf[13];
  uint8_t pm10_high = rx_buf[14];
  uint16_t pm10 = ((uint16_t)pm10_high << 8) | pm10_low;

  pms5003_reading reading = {
      .pm1 = (float)pm1, .pm2_5 = (float)pm2_5, .pm10 = (float)pm10};

  return reading;
}

static void on_uart_rx() {
  // TODO: make the uart1 dynamic
  watchdog_update();
  while (read && reading_i < MAX_READINGS && uart_is_readable(uart1)) {
    uint8_t ch = uart_getc(uart1);
    // start of a message
    if (ch == 0x42) {
      printf("pms5003 reading received\n");
      rx_i = 0;
    }

    // Bounds check before accessing array
    if (rx_i >= 32) {
      rx_i = 0;
      continue;
    }

    rx_buf[rx_i] = ch;
    rx_i++;
    // end of message
    if (rx_i == 31) {
      readings[reading_i] = extract_pm_values_from_rx_buf();
      printf("pm1: %f, pm2.5: %f, pm10: %f\n", readings[reading_i].pm1, readings[reading_i].pm2_5, readings[reading_i].pm10);
      reading_i++;
    }
  }
}

static unsigned char pms5003_command_prefix[] = {0x42, 0x4D};
void pms5003_init(pms5003_config *new_config, uart_inst_t *uart, uint8_t tx_pin,
                  uint8_t rx_pin, uint8_t enable_pin, uint8_t reset_pin) {
  gpio_set_function(tx_pin, UART_FUNCSEL_NUM(uart, tx_pin));
  gpio_set_function(rx_pin, UART_FUNCSEL_NUM(uart, rx_pin));
  uart_init(uart, 9600);
  uart_set_format(uart, 8, 1, UART_PARITY_NONE);
  irq_set_exclusive_handler(UART1_IRQ, on_uart_rx);
  irq_set_enabled(UART1_IRQ, true);
  uart_set_irq_enables(uart, false, false);

  // high level or suspending is normal working status, while low level is
  // sleeping mode.
  gpio_init(enable_pin);
  gpio_set_dir(enable_pin, GPIO_OUT);
  gpio_put(enable_pin, 0);

  // TODO: add hourly reset?
  // low resets
  // gpio_init(reset_pin);
  // gpio_set_dir(reset_pin, GPIO_OUT);
  // gpio_set_pulls(enable_pin, true, false); // pull up
  // gpio_put(enable_pin, 1);

  new_config->uart = uart;
  new_config->enable_pin = enable_pin;
  new_config->reset_pin = reset_pin;
}

static pms5003_reading compute_avarage_reading() {
  extern uint16_t reading_i;
  extern pms5003_reading readings[MAX_READINGS];

  float pm1_sum = 0;
  float pm2_5_sum = 0;
  float pm10_sum = 0;

  for (int i = 0; i < reading_i; i++) {
    pm1_sum += readings[i].pm1;
    pm2_5_sum += readings[i].pm2_5;
    pm10_sum += readings[i].pm10;
  }
  pms5003_reading average_reading = {.pm1 = pm1_sum / reading_i,
                                     .pm2_5 = pm2_5_sum / reading_i,
                                     .pm10 = pm10_sum / reading_i};
  return average_reading;
}

void pms5003_warmup(pms5003_config *config) { gpio_put(config->enable_pin, 1); }

void pms5003_start_reading(pms5003_config *config) {
  reading_i = 0;
  read = true;
  uart_set_irq_enables(config->uart, true, false);
}

pms5003_reading pms5003_finish_reading(pms5003_config *config) {
  printf("readings_i: %d\n", reading_i);
  read = false;
  uart_set_irq_enables(config->uart, false, false);
  gpio_put(config->enable_pin, 0);
  pms5003_reading average_reading = compute_avarage_reading();
  reading_i = 0;
  rx_i = 0;
  return average_reading;
}