
// ****************************************************************************
//
//                                 Main code
//
// ****************************************************************************
/* Example code to talk to a bme280 humidity/temperature/pressure sensor.

   NOTE: Ensure the device is capable of being driven at 3.3v NOT 5v. The Pico
   GPIO (and therefor SPI) cannot be used at 5v.

   You will need to use a level shifter on the SPI lines if you want to run the
   board at 5v.

   Connections on Raspberry Pi Pico board and a generic bme280 board, other
   boards may vary.

   GPIO 16 (pin 21) MISO/spi0_rx-> SDO/SDO on bme280 board
   GPIO 17 (pin 22) Chip select -> CSB/!CS on bme280 board
   GPIO 18 (pin 24) SCK/spi0_sclk -> SCL/SCK on bme280 board
   GPIO 19 (pin 25) MOSI/spi0_tx -> SDA/SDI on bme280 board
   3.3v (pin 3;6) -> VCC on bme280 board
   GND (pin 38)  -> GND on bme280 board

   Note: SPI devices can have a number of different naming schemes for pins. See
   the Wikipedia page at https://en.wikipedia.org/wiki/Serial_Peripheral_Interface
   for variations.

   This code uses a bunch of register definitions, and some compensation code derived
   from the Bosch datasheet which can be found here.
   https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bme280-ds002.pdf
*/

#include "include.h"

#define PIN_MISO 16
#define PIN_CS   17
#define PIN_SCK  18
#define PIN_MOSI 19

#define SPI_PORT spi0
#define READ_BIT 0x80

int32_t t_fine;

uint16_t dig_T1;
int16_t dig_T2, dig_T3;
uint16_t dig_P1;
int16_t dig_P2, dig_P3, dig_P4, dig_P5, dig_P6, dig_P7, dig_P8, dig_P9;
uint8_t dig_H1, dig_H3;
int8_t dig_H6;
int16_t dig_H2, dig_H4, dig_H5;

/* The following compensation functions are required to convert from the raw ADC
data from the chip to something usable. Each chip has a different set of
compensation parameters stored on the chip at point of manufacture, which are
read from the chip at startup and used inthese routines.
*/
int32_t compensate_temp(int32_t adc_T)
{
	int32_t var1, var2, T;
	var1 = ((((adc_T >> 3) - ((int32_t) dig_T1 << 1))) * ((int32_t) dig_T2)) >> 11;
	var2 = (((((adc_T >> 4) - ((int32_t) dig_T1)) * ((adc_T >> 4) - ((int32_t) dig_T1))) >> 12) * ((int32_t) dig_T3)) >> 14;

	t_fine = var1 + var2;
	T = (t_fine * 5 + 128) >> 8;
	return T;
}

uint32_t compensate_pressure(int32_t adc_P)
{
	int32_t var1, var2;
	uint32_t p;
	var1 = (((int32_t) t_fine) >> 1) - (int32_t) 64000;
	var2 = (((var1 >> 2) * (var1 >> 2)) >> 11) * ((int32_t) dig_P6);
	var2 = var2 + ((var1 * ((int32_t) dig_P5)) << 1);
	var2 = (var2 >> 2) + (((int32_t) dig_P4) << 16);
	var1 = (((dig_P3 * (((var1 >> 2) * (var1 >> 2)) >> 13)) >> 3) + ((((int32_t) dig_P2) * var1) >> 1)) >> 18;
	var1 = ((((32768 + var1)) * ((int32_t) dig_P1)) >> 15);
	if (var1 == 0) return 0;

	p = (((uint32_t) (((int32_t) 1048576) - adc_P) - (var2 >> 12))) * 3125;
	if (p < 0x80000000)
		p = (p << 1) / ((uint32_t) var1);
	else
		p = (p / (uint32_t) var1) * 2;

	var1 = (((int32_t) dig_P9) * ((int32_t) (((p >> 3) * (p >> 3)) >> 13))) >> 12;
	var2 = (((int32_t) (p >> 2)) * ((int32_t) dig_P8)) >> 13;
	p = (uint32_t) ((int32_t) p + ((var1 + var2 + dig_P7) >> 4));

	return p;
}

uint32_t compensate_humidity(int32_t adc_H)
{
	int32_t v_x1_u32r;
	v_x1_u32r = (t_fine - ((int32_t) 76800));
	v_x1_u32r = (((((adc_H << 14) - (((int32_t) dig_H4) << 20) - (((int32_t) dig_H5) * v_x1_u32r)) +
		((int32_t) 16384)) >> 15) * (((((((v_x1_u32r * ((int32_t) dig_H6)) >> 10) * 
		(((v_x1_u32r *  ((int32_t) dig_H3)) >> 11) + ((int32_t) 32768))) >> 10) + 
		((int32_t) 2097152)) * ((int32_t) dig_H2) + 8192) >> 14));
	v_x1_u32r = (v_x1_u32r - (((((v_x1_u32r >> 15) * (v_x1_u32r >> 15)) >> 7) * ((int32_t) dig_H1)) >> 4));
	v_x1_u32r = (v_x1_u32r < 0 ? 0 : v_x1_u32r);
	v_x1_u32r = (v_x1_u32r > 419430400 ? 419430400 : v_x1_u32r);

	return (uint32_t) (v_x1_u32r >> 12);
}

static inline void cs_select()
{
	asm volatile("nop \n nop \n nop");
	gpio_put(PIN_CS, 0);  // Active low
	asm volatile("nop \n nop \n nop");
}

static inline void cs_deselect()
{
	asm volatile("nop \n nop \n nop");
	gpio_put(PIN_CS, 1);
	asm volatile("nop \n nop \n nop");
}

static void write_register(uint8_t reg, uint8_t data)
{
	uint8_t buf[2];
	buf[0] = reg & 0x7f;  // remove read bit as this is a write
	buf[1] = data;
	cs_select();
	spi_write_blocking(SPI_PORT, buf, 2);
	cs_deselect();
	sleep_ms(10);
}

static void read_registers(uint8_t reg, uint8_t *buf, uint16_t len)
{
	// For this particular device, we send the device the register we want to read
	// first, then subsequently read from the device. The register is auto incrementing
	// so we don't need to keep sending the register we want, just the first.
	reg |= READ_BIT;
	cs_select();
	spi_write_blocking(SPI_PORT, &reg, 1);
	sleep_ms(10);
	spi_read_blocking(SPI_PORT, 0, buf, len);
	cs_deselect();
	sleep_ms(10);
}

/* This function reads the manufacturing assigned compensation parameters from the device */
void read_compensation_parameters()
{
	uint8_t buffer[26];

	read_registers(0x88, buffer, 24);

	dig_T1 = buffer[0] | (buffer[1] << 8);
	dig_T2 = buffer[2] | (buffer[3] << 8);
	dig_T3 = buffer[4] | (buffer[5] << 8);

	dig_P1 = buffer[6] | (buffer[7] << 8);
	dig_P2 = buffer[8] | (buffer[9] << 8);
	dig_P3 = buffer[10] | (buffer[11] << 8);
	dig_P4 = buffer[12] | (buffer[13] << 8);
	dig_P5 = buffer[14] | (buffer[15] << 8);
	dig_P6 = buffer[16] | (buffer[17] << 8);
	dig_P7 = buffer[18] | (buffer[19] << 8);
	dig_P8 = buffer[20] | (buffer[21] << 8);
	dig_P9 = buffer[22] | (buffer[23] << 8);

	dig_H1 = buffer[25];

	read_registers(0xE1, buffer, 8);

	dig_H2 = buffer[0] | (buffer[1] << 8);
	dig_H3 = (int8_t) buffer[2];
	dig_H4 = buffer[3] << 4 | (buffer[4] & 0xf);
	dig_H5 = (buffer[5] >> 4) | (buffer[6] << 4);
	dig_H6 = (int8_t) buffer[7];
}

static void bme280_read_raw(int32_t *humidity, int32_t *pressure, int32_t *temperature)
{
	uint8_t buffer[8];

	read_registers(0xF7, buffer, 8);
	*pressure = ((uint32_t) buffer[0] << 12) | ((uint32_t) buffer[1] << 4) | (buffer[2] >> 4);
	*temperature = ((uint32_t) buffer[3] << 12) | ((uint32_t) buffer[4] << 4) | (buffer[5] >> 4);
	*humidity = (uint32_t) buffer[6] << 8 | buffer[7];
}

int main()
{
	stdio_init_all();

	printf("Hello, bme280! Reading raw data from registers via SPI...\n");

	// This example will use SPI0 at 0.5MHz.
	spi_init(SPI_PORT, 500 * 1000);
	gpio_set_function(PIN_MISO, GPIO_FUNC_SPI);
	gpio_set_function(PIN_SCK, GPIO_FUNC_SPI);
	gpio_set_function(PIN_MOSI, GPIO_FUNC_SPI);

	// Chip select is active-low, so we'll initialise it to a driven-high state
	gpio_init(PIN_CS);
	gpio_set_dir(PIN_CS, GPIO_OUT);
	gpio_put(PIN_CS, 1);

	// See if SPI is working - interrograte the device for its I2C ID number, should be 0x60
	uint8_t id;
	read_registers(0xD0, &id, 1);
	printf("Chip ID is 0x%x\n", id);

	read_compensation_parameters();

	write_register(0xF2, 0x1); // Humidity oversampling register - going for x1
	write_register(0xF4, 0x27);// Set rest of oversampling modes and run mode to normal

	int32_t humidity, pressure, temperature;

	while (1)
	{
		bme280_read_raw(&humidity, &pressure, &temperature);

		// These are the raw numbers from the chip, so we need to run through the
		// compensations to get human understandable numbers
		pressure = compensate_pressure(pressure);
		temperature = compensate_temp(temperature);
		humidity = compensate_humidity(humidity);

		printf("Humidity = %.2f%%\n", humidity / 1024.0);
		printf("Pressure = %dPa\n", pressure);
		printf("Temp. = %.2fC\n", temperature / 100.0);

		sleep_ms(1000);
	}

	return 0;
}
