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mpl3115a2_i2c
for Raspberry Pi Picoโ„ข 2 W, submitted by flashmypico

Fetching config...

/**
* Copyright (c) 2021 Raspberry Pi (Trading) Ltd.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <stdio.h>
#include "pico/stdlib.h"
#include "pico/binary_info.h"
#include "hardware/gpio.h"
#include "hardware/i2c.h"
/* Example code to talk to an MPL3115A2 altimeter sensor via I2C
See accompanying documentation in README.adoc or the C++ SDK booklet.
Connections on Raspberry Pi Pico board, other boards may vary.
GPIO PICO_DEFAULT_I2C_SDA_PIN (On Pico this is 4 (pin 6)) -> SDA on MPL3115A2 board
GPIO PICO_DEFAULT_I2C_SCK_PIN (On Pico this is 5 (pin 7)) -> SCL on MPL3115A2 board
GPIO 16 -> INT1 on MPL3115A2 board
3.3v (pin 36) -> VCC on MPL3115A2 board
GND (pin 38) -> GND on MPL3115A2 board
*/
// 7-bit address
#define ADDR 0x60
#define INT1_PIN _u(16)
// following definitions only valid for F_MODE > 0 (ie. if FIFO enabled)
#define MPL3115A2_F_DATA _u(0x01)
#define MPL3115A2_F_STATUS _u(0x00)
#define MPL3115A2_F_SETUP _u(0x0F)
#define MPL3115A2_INT_SOURCE _u(0x12)
#define MPL3115A2_CTRLREG1 _u(0x26)
#define MPL3115A2_CTRLREG2 _u(0x27)
#define MPL3115A2_CTRLREG3 _u(0x28)
#define MPL3115A2_CTRLREG4 _u(0x29)
#define MPL3115A2_CTRLREG5 _u(0x2A)
#define MPL3115A2_PT_DATA_CFG _u(0x13)
#define MPL3115A2_OFF_P _u(0x2B)
#define MPL3115A2_OFF_T _u(0x2C)
#define MPL3115A2_OFF_H _u(0x2D)
#define MPL3115A2_FIFO_DISABLED _u(0x00)
#define MPL3115A2_FIFO_STOP_ON_OVERFLOW _u(0x80)
#define MPL3115A2_FIFO_SIZE 32
#define MPL3115A2_DATA_BATCH_SIZE 5
#define MPL3115A2_ALTITUDE_NUM_REGS 3
#define MPL3115A2_ALTITUDE_INT_SIZE 20
#define MPL3115A2_TEMPERATURE_INT_SIZE 12
#define MPL3115A2_NUM_FRAC_BITS 4
#define PARAM_ASSERTIONS_ENABLE_I2C 1
volatile uint8_t fifo_data[MPL3115A2_FIFO_SIZE * MPL3115A2_DATA_BATCH_SIZE];
volatile bool has_new_data = false;
struct mpl3115a2_data_t {
// Q8.4 fixed point
float temperature;
// Q16.4 fixed-point
float altitude;
};
void copy_to_vbuf(uint8_t buf1[], volatile uint8_t buf2[], uint buflen) {
for (size_t i = 0; i < buflen; i++) {
buf2[i] = buf1[i];
}
}
#ifdef i2c_default
void mpl3115a2_read_fifo(volatile uint8_t fifo_buf[]) {
// drains the 160 byte FIFO
uint8_t reg = MPL3115A2_F_DATA;
uint8_t buf[MPL3115A2_FIFO_SIZE * MPL3115A2_DATA_BATCH_SIZE];
i2c_write_blocking(i2c_default, ADDR, &reg, 1, true);
// burst read 160 bytes from fifo
i2c_read_blocking(i2c_default, ADDR, buf, MPL3115A2_FIFO_SIZE * MPL3115A2_DATA_BATCH_SIZE, false);
copy_to_vbuf(buf, fifo_buf, MPL3115A2_FIFO_SIZE * MPL3115A2_DATA_BATCH_SIZE);
}
uint8_t mpl3115a2_read_reg(uint8_t reg) {
uint8_t read;
i2c_write_blocking(i2c_default, ADDR, &reg, 1, true); // keep control of bus
i2c_read_blocking(i2c_default, ADDR, &read, 1, false);
return read;
}
void mpl3115a2_init() {
// set as altimeter with oversampling ratio of 128
uint8_t buf[] = {MPL3115A2_CTRLREG1, 0xB8};
i2c_write_blocking(i2c_default, ADDR, buf, 2, false);
// set data refresh every 2 seconds, 0 next bits as we're not using those interrupts
buf[0] = MPL3115A2_CTRLREG2, buf[1] = 0x00;
i2c_write_blocking(i2c_default, ADDR, buf, 2, false);
// set both interrupts pins to active low and enable internal pullups
buf[0] = MPL3115A2_CTRLREG3, buf[1] = 0x01;
i2c_write_blocking(i2c_default, ADDR, buf, 2, false);
// enable FIFO interrupt
buf[0] = MPL3115A2_CTRLREG4, buf[1] = 0x40;
i2c_write_blocking(i2c_default, ADDR, buf, 2, false);
// tie FIFO interrupt to pin INT1
buf[0] = MPL3115A2_CTRLREG5, buf[1] = 0x40;
i2c_write_blocking(i2c_default, ADDR, buf, 2, false);
// set p, t and h offsets here if needed
// eg. 2's complement number: 0xFF subtracts 1 meter
//buf[0] = MPL3115A2_OFF_H, buf[1] = 0xFF;
//i2c_write_blocking(i2c_default, ADDR, buf, 2, false);
// do not accept more data on FIFO overflow
buf[0] = MPL3115A2_F_SETUP, buf[1] = MPL3115A2_FIFO_STOP_ON_OVERFLOW;
i2c_write_blocking(i2c_default, ADDR, buf, 2, false);
// set device active
buf[0] = MPL3115A2_CTRLREG1, buf[1] = 0xB9;
i2c_write_blocking(i2c_default, ADDR, buf, 2, false);
}
void gpio_callback(uint gpio, __unused uint32_t events) {
// if we had enabled more than 2 interrupts on same pin, then we should read
// INT_SOURCE reg to find out which interrupt triggered
// we can filter by which GPIO was triggered
if (gpio == INT1_PIN) {
// FIFO overflow interrupt
// watermark bits set to 0 in F_SETUP reg, so only possible event is an overflow
// otherwise, we would read F_STATUS to confirm it was an overflow
printf("FIFO overflow!\n");
// drain the fifo
mpl3115a2_read_fifo(fifo_data);
// read status register to clear interrupt bit
mpl3115a2_read_reg(MPL3115A2_F_STATUS);
has_new_data = true;
}
}
#endif
void mpl3115a2_convert_fifo_batch(uint8_t start, volatile uint8_t buf[], struct mpl3115a2_data_t *data) {
// convert a batch of fifo data into temperature and altitude data
// 3 altitude registers: MSB (8 bits), CSB (8 bits) and LSB (4 bits, starting from MSB)
// first two are integer bits (2's complement) and LSB is fractional bits -> makes 20 bit signed integer
int32_t h = (int32_t) buf[start] << 24;
h |= (int32_t) buf[start + 1] << 16;
h |= (int32_t) buf[start + 2] << 8;
data->altitude = ((float)h) / 65536.f;
// 2 temperature registers: MSB (8 bits) and LSB (4 bits, starting from MSB)
// first 8 are integer bits with sign and LSB is fractional bits -> 12 bit signed integer
int16_t t = (int16_t) buf[start + 3] << 8;
t |= (int16_t) buf[start + 4];
data->temperature = ((float)t) / 256.f;
}
int main() {
stdio_init_all();
#if !defined(i2c_default) || !defined(PICO_DEFAULT_I2C_SDA_PIN) || !defined(PICO_DEFAULT_I2C_SCL_PIN)
#warning i2c / mpl3115a2_i2c example requires a board with I2C pins
puts("Default I2C pins were not defined");
return 0;
#else
printf("Hello, MPL3115A2. Waiting for something to interrupt me!...\n");
// use default I2C0 at 400kHz, I2C is active low
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);
gpio_init(INT1_PIN);
gpio_pull_up(INT1_PIN); // pull it up even more!
// add program information for picotool
bi_decl(bi_program_name("Example in the pico-examples library for the MPL3115A2 altimeter"));
bi_decl(bi_1pin_with_name(16, "Interrupt pin 1"));
bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C));
mpl3115a2_init();
gpio_set_irq_enabled_with_callback(INT1_PIN, GPIO_IRQ_LEVEL_LOW, true, &gpio_callback);
while (1) {
// as interrupt data comes in, let's print the 32 sample average
if (has_new_data) {
float tsum = 0, hsum = 0;
struct mpl3115a2_data_t data;
for (int i = 0; i < MPL3115A2_FIFO_SIZE; i++) {
mpl3115a2_convert_fifo_batch(i * MPL3115A2_DATA_BATCH_SIZE, fifo_data, &data);
tsum += data.temperature;
hsum += data.altitude;
}
printf("%d sample average -> t: %.4f C, h: %.4f m\n", MPL3115A2_FIFO_SIZE, tsum / MPL3115A2_FIFO_SIZE,
hsum / MPL3115A2_FIFO_SIZE);
has_new_data = false;
}
sleep_ms(10);
};
#endif
}
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This firmware image was imported from the pico-examples repository. 


Copyright 2020 (c) 2020 Raspberry Pi (Trading) Ltd.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following
   disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
   disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products
   derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Homepage: https://github.com/raspberrypi/pico-examples
Repository: https://github.com/raspberrypi/pico-examples/tree/master/i2c/mpl3115a2_i2c

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