/** * 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/i2c.h" /* Example code to talk to a MMA8451 triple-axis accelerometer. This reads and writes to registers on the board. Connections on Raspberry Pi Pico board, other boards may vary. GPIO PICO_DEFAULT_I2C_SDA_PIN (On Pico this is GP4 (physical pin 6)) -> SDA on MMA8451 board GPIO PICO_DEFAULT_I2C_SCK_PIN (On Pico this is GP5 (physical pin 7)) -> SCL on MMA8451 board VSYS (physical pin 39) -> VDD on MMA8451 board GND (physical pin 38) -> GND on MMA8451 board */ const uint8_t ADDRESS = 0x1D; //hardware registers const uint8_t REG_X_MSB = 0x01; const uint8_t REG_X_LSB = 0x02; const uint8_t REG_Y_MSB = 0x03; const uint8_t REG_Y_LSB = 0x04; const uint8_t REG_Z_MSB = 0x05; const uint8_t REG_Z_LSB = 0x06; const uint8_t REG_DATA_CFG = 0x0E; const uint8_t REG_CTRL_REG1 = 0x2A; // Set the range and precision for the data const uint8_t range_config = 0x01; // 0x00 for ±2g, 0x01 for ±4g, 0x02 for ±8g const float count = 2048; // 4096 for ±2g, 2048 for ±4g, 1024 for ±8g uint8_t buf[2]; float mma8451_convert_accel(uint16_t raw_accel) { float acceleration; // Acceleration is read as a multiple of g (gravitational acceleration on the Earth's surface) // Check if acceleration < 0 and convert to decimal accordingly if ((raw_accel & 0x2000) == 0x2000) { raw_accel &= 0x1FFF; acceleration = (-8192 + (float) raw_accel) / count; } else { acceleration = (float) raw_accel / count; } acceleration *= 9.81f; return acceleration; } #ifdef i2c_default void mma8451_set_state(uint8_t state) { buf[0] = REG_CTRL_REG1; buf[1] = state; // Set RST bit to 1 i2c_write_blocking(i2c_default, ADDRESS, buf, 2, false); } #endif int main() { stdio_init_all(); #if !defined(i2c_default) || !defined(PICO_DEFAULT_I2C_SDA_PIN) || !defined(PICO_DEFAULT_I2C_SCL_PIN) #warning i2c/mma8451_i2c example requires a board with I2C pins puts("Default I2C pins were not defined"); #else printf("Hello, MMA8451! Reading raw data from registers...\n"); // This example will use I2C0 on the default SDA and SCL pins (4, 5 on a Pico) i2c_init(i2c_default, 400 * 1000); gpio_set_function(PICO_DEFAULT_I2C_SDA_PIN, GPIO_FUNC_I2C); gpio_set_function(PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C); gpio_pull_up(PICO_DEFAULT_I2C_SDA_PIN); gpio_pull_up(PICO_DEFAULT_I2C_SCL_PIN); // Make the I2C pins available to picotool bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C)); float x_acceleration; float y_acceleration; float z_acceleration; // Enable standby mode mma8451_set_state(0x00); // Edit configuration while in standby mode buf[0] = REG_DATA_CFG; buf[1] = range_config; i2c_write_blocking(i2c_default, ADDRESS, buf, 2, false); // Enable active mode mma8451_set_state(0x01); while (1) { // Start reading acceleration registers for 2 bytes i2c_write_blocking(i2c_default, ADDRESS, &REG_X_MSB, 1, true); i2c_read_blocking(i2c_default, ADDRESS, buf, 2, false); x_acceleration = mma8451_convert_accel(buf[0] << 6 | buf[1] >> 2); i2c_write_blocking(i2c_default, ADDRESS, &REG_Y_MSB, 1, true); i2c_read_blocking(i2c_default, ADDRESS, buf, 2, false); y_acceleration = mma8451_convert_accel(buf[0] << 6 | buf[1] >> 2); i2c_write_blocking(i2c_default, ADDRESS, &REG_Z_MSB, 1, true); i2c_read_blocking(i2c_default, ADDRESS, buf, 2, false); z_acceleration = mma8451_convert_accel(buf[0] << 6 | buf[1] >> 2); // Display acceleration values printf("ACCELERATION VALUES: \n"); printf("X acceleration: %.6fms^-2\n", x_acceleration); printf("Y acceleration: %.6fms^-2\n", y_acceleration); printf("Z acceleration: %.6fms^-2\n", z_acceleration); sleep_ms(500); // Clear terminal printf("\033[1;1H\033[2J"); } #endif }

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


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