/** * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include <stdio.h> #include <string.h> #include "pico/stdlib.h" #include "pico/binary_info.h" #include "hardware/spi.h" /* 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 therefore 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 36) -> 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 */ #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 in these 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); } #ifdef PICO_DEFAULT_SPI_CSN_PIN static inline void cs_select() { asm volatile("nop \n nop \n nop"); gpio_put(PICO_DEFAULT_SPI_CSN_PIN, 0); // Active low asm volatile("nop \n nop \n nop"); } static inline void cs_deselect() { asm volatile("nop \n nop \n nop"); gpio_put(PICO_DEFAULT_SPI_CSN_PIN, 1); asm volatile("nop \n nop \n nop"); } #endif #if defined(spi_default) && defined(PICO_DEFAULT_SPI_CSN_PIN) 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_default, 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_default, &reg, 1); sleep_ms(10); spi_read_blocking(spi_default, 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, 26); 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]; // 0xA1 read_registers(0xE1, buffer, 8); dig_H2 = buffer[0] | (buffer[1] << 8); // 0xE1 | 0xE2 dig_H3 = (int8_t) buffer[2]; // 0xE3 dig_H4 = buffer[3] << 4 | (buffer[4] & 0xf); // 0xE4 | 0xE5[3:0] dig_H5 = (buffer[4] >> 4) | (buffer[5] << 4); // 0xE5[7:4] | 0xE6 dig_H6 = (int8_t) buffer[6]; // 0xE7 } 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]; } #endif int main() { stdio_init_all(); #if !defined(spi_default) || !defined(PICO_DEFAULT_SPI_SCK_PIN) || !defined(PICO_DEFAULT_SPI_TX_PIN) || !defined(PICO_DEFAULT_SPI_RX_PIN) || !defined(PICO_DEFAULT_SPI_CSN_PIN) #warning spi/bme280_spi example requires a board with SPI pins puts("Default SPI pins were not defined"); #else printf("Hello, bme280! Reading raw data from registers via SPI...\n"); // This example will use SPI0 at 0.5MHz. spi_init(spi_default, 500 * 1000); gpio_set_function(PICO_DEFAULT_SPI_RX_PIN, GPIO_FUNC_SPI); gpio_set_function(PICO_DEFAULT_SPI_SCK_PIN, GPIO_FUNC_SPI); gpio_set_function(PICO_DEFAULT_SPI_TX_PIN, GPIO_FUNC_SPI); // Make the SPI pins available to picotool bi_decl(bi_3pins_with_func(PICO_DEFAULT_SPI_RX_PIN, PICO_DEFAULT_SPI_TX_PIN, PICO_DEFAULT_SPI_SCK_PIN, GPIO_FUNC_SPI)); // Chip select is active-low, so we'll initialise it to a driven-high state gpio_init(PICO_DEFAULT_SPI_CSN_PIN); gpio_set_dir(PICO_DEFAULT_SPI_CSN_PIN, GPIO_OUT); gpio_put(PICO_DEFAULT_SPI_CSN_PIN, 1); // Make the CS pin available to picotool bi_decl(bi_1pin_with_name(PICO_DEFAULT_SPI_CSN_PIN, "SPI CS")); // 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 temperature = compensate_temp(temperature); pressure = compensate_pressure(pressure); 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); } #endif }

This firmware image was imported from the pico-examples repository. 


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