129 lines
4.2 KiB
C
129 lines
4.2 KiB
C
/**
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* Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include <stdio.h>
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#include <string.h>
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#include "pico/stdlib.h"
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#include "pico/binary_info.h"
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#include "hardware/i2c.h"
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/* Example code to talk to a MMA8451 triple-axis accelerometer.
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This reads and writes to registers on the board.
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Connections on Raspberry Pi Pico board, other boards may vary.
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GPIO PICO_DEFAULT_I2C_SDA_PIN (On Pico this is GP4 (physical pin 6)) -> SDA on MMA8451 board
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GPIO PICO_DEFAULT_I2C_SCK_PIN (On Pico this is GP5 (physcial pin 7)) -> SCL on MMA8451 board
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VSYS (physical pin 39) -> VDD on MMA8451 board
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GND (physical pin 38) -> GND on MMA8451 board
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*/
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const uint8_t ADDRESS = 0x1D;
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//hardware registers
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const uint8_t REG_X_MSB = 0x01;
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const uint8_t REG_X_LSB = 0x02;
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const uint8_t REG_Y_MSB = 0x03;
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const uint8_t REG_Y_LSB = 0x04;
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const uint8_t REG_Z_MSB = 0x05;
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const uint8_t REG_Z_LSB = 0x06;
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const uint8_t REG_DATA_CFG = 0x0E;
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const uint8_t REG_CTRL_REG1 = 0x2A;
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// Set the range and precision for the data
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const uint8_t range_config = 0x01; // 0x00 for ±2g, 0x01 for ±4g, 0x02 for ±8g
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const float count = 2048; // 4096 for ±2g, 2048 for ±4g, 1024 for ±8g
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uint8_t buf[2];
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float mma8451_convert_accel(uint16_t raw_accel) {
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float acceleration;
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// Acceleration is read as a multiple of g (gravitational acceleration on the Earth's surface)
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// Check if acceleration < 0 and convert to decimal accordingly
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if ((raw_accel & 0x2000) == 0x2000) {
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raw_accel &= 0x1FFF;
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acceleration = (-8192 + (float) raw_accel) / count;
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} else {
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acceleration = (float) raw_accel / count;
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}
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acceleration *= 9.81f;
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return acceleration;
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}
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#ifdef i2c_default
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void mma8451_set_state(uint8_t state) {
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buf[0] = REG_CTRL_REG1;
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buf[1] = state; // Set RST bit to 1
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i2c_write_blocking(i2c_default, ADDRESS, buf, 2, false);
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}
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#endif
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int main() {
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stdio_init_all();
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#if !defined(i2c_default) || !defined(PICO_DEFAULT_I2C_SDA_PIN) || !defined(PICO_DEFAULT_I2C_SCL_PIN)
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#warning i2c/mma8451_i2c example requires a board with I2C pins
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puts("Default I2C pins were not defined");
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#else
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printf("Hello, MMA8451! Reading raw data from registers...\n");
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// This example will use I2C0 on the default SDA and SCL pins (4, 5 on a Pico)
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i2c_init(i2c_default, 400 * 1000);
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gpio_set_function(PICO_DEFAULT_I2C_SDA_PIN, GPIO_FUNC_I2C);
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gpio_set_function(PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C);
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gpio_pull_up(PICO_DEFAULT_I2C_SDA_PIN);
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gpio_pull_up(PICO_DEFAULT_I2C_SCL_PIN);
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// Make the I2C pins available to picotool
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bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C));
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float x_acceleration;
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float y_acceleration;
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float z_acceleration;
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// Enable standby mode
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mma8451_set_state(0x00);
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// Edit configuration while in standby mode
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buf[0] = REG_DATA_CFG;
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buf[1] = range_config;
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i2c_write_blocking(i2c_default, ADDRESS, buf, 2, false);
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// Enable active mode
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mma8451_set_state(0x01);
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while (1) {
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// Start reading acceleration registers for 2 bytes
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i2c_write_blocking(i2c_default, ADDRESS, ®_X_MSB, 1, true);
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i2c_read_blocking(i2c_default, ADDRESS, buf, 2, false);
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x_acceleration = mma8451_convert_accel(buf[0] << 6 | buf[1] >> 2);
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i2c_write_blocking(i2c_default, ADDRESS, ®_Y_MSB, 1, true);
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i2c_read_blocking(i2c_default, ADDRESS, buf, 2, false);
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y_acceleration = mma8451_convert_accel(buf[0] << 6 | buf[1] >> 2);
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i2c_write_blocking(i2c_default, ADDRESS, ®_Z_MSB, 1, true);
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i2c_read_blocking(i2c_default, ADDRESS, buf, 2, false);
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z_acceleration = mma8451_convert_accel(buf[0] << 6 | buf[1] >> 2);
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// Display acceleration values
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printf("ACCELERATION VALUES: \n");
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printf("X acceleration: %.6fms^-2\n", x_acceleration);
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printf("Y acceleration: %.6fms^-2\n", y_acceleration);
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printf("Z acceleration: %.6fms^-2\n", z_acceleration);
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sleep_ms(500);
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// Clear terminal
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printf("\e[1;1H\e[2J");
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}
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#endif
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}
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