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sensor_max1247: add library to read ADC values from MAX1247

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King Kévin 2020-12-07 19:11:07 +01:00
parent fb088e6057
commit 974ca75027
2 changed files with 102 additions and 0 deletions
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lib/sensor_max1247.c Normal file
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/** library to communication with Maxim MAX1247 12-bit 4-channel ADC using SPI
* @file
* @author King Kévin <kingkevin@cuvoodoo.info>
* @copyright SPDX-License-Identifier: GPL-3.0-or-later
* @date 2020
* @note peripherals used: SPI @ref sensor_max1247_spi
*/
/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdlib.h> // general utilities
#include <stdbool.h> // boolean utilities
/* STM32 (including CM3) libraries */
#include <libopencmsis/core_cm3.h> // Cortex M3 utilities
#include <libopencm3/stm32/rcc.h> // real-time control clock library
#include <libopencm3/stm32/gpio.h> // general purpose input output library
#include <libopencm3/stm32/spi.h> // SPI library
/* own libraries */
#include "global.h" // common methods
#include "sensor_max1247.h" // own definitions
/** @defgroup sensor_max1247_spi SPI peripheral used to communicate with the AS3935
* @{
*/
#define SENSOR_MAX1247_SPI 2 /**< SPI peripheral */
/** @} */
void sensor_max1247_setup(void)
{
// setup SPI
rcc_periph_clock_enable(RCC_SPI_SCK_PORT(SENSOR_MAX1247_SPI)); // enable clock for GPIO peripheral for clock signal
gpio_set_mode(SPI_SCK_PORT(SENSOR_MAX1247_SPI), GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, SPI_SCK_PIN(SENSOR_MAX1247_SPI)); // set SCK as output (clock speed will be negotiated later)
rcc_periph_clock_enable(RCC_SPI_MOSI_PORT(SENSOR_MAX1247_SPI)); // enable clock for GPIO peripheral for MOSI signal
gpio_set_mode(SPI_MOSI_PORT(SENSOR_MAX1247_SPI), GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, SPI_MOSI_PIN(SENSOR_MAX1247_SPI)); // set MOSI as output
rcc_periph_clock_enable(RCC_SPI_MISO_PORT(SENSOR_MAX1247_SPI)); // enable clock for GPIO peripheral for MISO signal
gpio_set_mode(SPI_MISO_PORT(SENSOR_MAX1247_SPI), GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, SPI_MISO_PIN(SENSOR_MAX1247_SPI)); // set MISO as input
rcc_periph_clock_enable(RCC_SPI_NSS_PORT(SENSOR_MAX1247_SPI)); // enable clock for GPIO peripheral for NSS (CS) signal
gpio_set_mode(SPI_NSS_PORT(SENSOR_MAX1247_SPI), GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, SPI_NSS_PIN(SENSOR_MAX1247_SPI)); // set NSS (CS) as output
rcc_periph_clock_enable(RCC_AFIO); // enable clock for SPI alternate function
rcc_periph_clock_enable(RCC_SPI(SENSOR_MAX1247_SPI)); // enable clock for SPI peripheral
spi_reset(SPI(SENSOR_MAX1247_SPI)); // clear SPI values to default
spi_init_master(SPI(SENSOR_MAX1247_SPI), SPI_CR1_BAUDRATE_FPCLK_DIV_64, SPI_CR1_CPOL_CLK_TO_0_WHEN_IDLE, SPI_CR1_CPHA_CLK_TRANSITION_1, SPI_CR1_DFF_8BIT, SPI_CR1_MSBFIRST); // initialise SPI as master, divide clock by 64 (72E6/64=1125 kHz, max MAX1247 SCK is 2 MHz, maximum SPI PCLK clock is 72 MHz, depending on which SPI is used), set clock polarity to idle low, set clock phase to do bit change on falling edge (polarity depends on clock phase), use 8 bits frames (the control is 8-bit long, and the conversion response 16-bit), use MSb first
spi_set_full_duplex_mode(SPI(SENSOR_MAX1247_SPI)); // ensure we are in full duplex mode
spi_enable_software_slave_management(SPI(SENSOR_MAX1247_SPI)); // control NSS (CS) manually
spi_set_nss_high(SPI(SENSOR_MAX1247_SPI)); // set NSS high (internally) so we can output
spi_disable_ss_output(SPI(SENSOR_MAX1247_SPI)); // disable NSS output since we control CS manually
gpio_set(SPI_NSS_PORT(SENSOR_MAX1247_SPI), SPI_NSS_PIN(SENSOR_MAX1247_SPI)); // set CS high to unselect device
// sadly we can't use the interrupts as events to sleep (WFE) since sleep disables also communication (e.g. going to sleep until Rx buffer is not empty prevents transmission)
spi_enable(SPI(SENSOR_MAX1247_SPI)); // enable SPI
}
void sensor_max1247_release(void)
{
spi_reset(SPI(SENSOR_MAX1247_SPI));
spi_disable(SPI(SENSOR_MAX1247_SPI));
rcc_periph_clock_disable(RCC_SPI(SENSOR_MAX1247_SPI));
gpio_set_mode(SPI_NSS_PORT(SENSOR_MAX1247_SPI), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, SPI_NSS_PIN(SENSOR_MAX1247_SPI));
gpio_set_mode(SPI_MISO_PORT(SENSOR_MAX1247_SPI), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, SPI_MISO_PIN(SENSOR_MAX1247_SPI));
gpio_set_mode(SPI_MOSI_PORT(SENSOR_MAX1247_SPI), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, SPI_MOSI_PIN(SENSOR_MAX1247_SPI));
gpio_set_mode(SPI_SCK_PORT(SENSOR_MAX1247_SPI), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, SPI_SCK_PIN(SENSOR_MAX1247_SPI));
}
uint16_t sensor_max1247_read(uint8_t channel)
{
if (channel > 3) { // ensure we read only from one of the 4 available channels
return UINT16_MAX;
}
gpio_clear(SPI_NSS_PORT(SENSOR_MAX1247_SPI), SPI_NSS_PIN(SENSOR_MAX1247_SPI)); // set CS low to select device
const uint8_t channels[4] = { 1, 5, 2, 6 }; // SEL bits corresponding to channel (in single ended mode)
uint8_t spi_in = spi_xfer(SPI(SENSOR_MAX1247_SPI), 0x8e | (channels[channel] << 4)); // send conversion control (START bit set, unipolar, single ended, internal clock mode)
sleep_us(8); // wait for conversion to finish (max. 7.5 µs using internal clock)
spi_in = spi_xfer(SPI(SENSOR_MAX1247_SPI), 0); // read first conversion bytes
const uint16_t value = (spi_in << 8) + spi_xfer(SPI(SENSOR_MAX1247_SPI), 0); // read second conversion byte
gpio_set(SPI_NSS_PORT(SENSOR_MAX1247_SPI), SPI_NSS_PIN(SENSOR_MAX1247_SPI)); // set CS high to select device
if ((value & 0x8000) || (value & 0x0007)) { // ensure it has one leading and 3 trailing zeros
return UINT16_MAX;
}
return value >> 3;
}

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lib/sensor_max1247.h Normal file
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/** library to communication with Maxim MAX1247 12-bit 4-channel ADC using SPI
* @file
* @author King Kévin <kingkevin@cuvoodoo.info>
* @copyright SPDX-License-Identifier: GPL-3.0-or-later
* @date 2020
* @note peripherals used: SPI @ref sensor_max1247_spi
*/
#pragma once
/** setup peripherals to communicate with sensor
* @note the sensor configuration will be set to default and powered down
*/
void sensor_max1247_setup(void);
/** release peripherals used to communicate with sensor */
void sensor_max1247_release(void);
/** read conversion from channel
* @param[in] channel which of the 4 channels to convert
* @return 12-bit conversion value (0xffff if error)
*/
uint16_t sensor_max1247_read(uint8_t channel);