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[LTD noup] drivers: sensor: add stm32f401x temperature driver
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There is an issue with this driver.

At present, there's no good way for board-level
configuration (specifically, the voltages on the V_REF- and V_REF+
external pins, which are needed to convert ADC values to volts) to be
made available portably to drivers.

Hack around this here by hard-coding reasonable defaults of 0V for
V_REF- and 3.3V for V_REF+.

Signed-off-by: Marti Bolivar <[email protected]>
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@rsalveti
Marti Bolivar authored and rsalveti committed Jun 1, 2017
1 parent 52ce7ab commit e97c7b6
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Showing 2 changed files with 223 additions and 6 deletions.
26 changes: 26 additions & 0 deletions drivers/sensor/stm32/temp_stm32.h
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@@ -0,0 +1,26 @@
/*
* Copyright (c) 2017 Linaro Limited.
*
* SPDX-License-Identifier: Apache-2.0
*/

#ifndef _STM32_TEMP_H_
#define _STM32_TEMP_H_

#include <stdint.h>

#include <device.h>
#include <soc.h>

struct temp_stm32_config {
ADC_TypeDef *adc;
ADC_Common_TypeDef *adc_common;
u8_t adc_channel;
struct stm32_pclken pclken;
};

struct temp_stm32_data {
struct device *clock;
};

#endif /* _STM32_TEMP_H_ */
203 changes: 197 additions & 6 deletions drivers/sensor/stm32/temp_stm32f401x.c
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Expand Up @@ -15,22 +15,166 @@
* as 45 degrees C.
*/

#include <device.h>
#define SYS_LOG_DOMAIN "TEMPSTM32F401"
#define SYS_LOG_LEVEL CONFIG_SYS_LOG_SENSOR_LEVEL

#include <drivers/clock_control/stm32_clock_control.h>
#include <errno.h>
#include <logging/sys_log.h>
#include <misc/__assert.h>
#include <sensor.h>

/* TODO */
#include "temp_stm32.h"

#define DEV_CFG(dev) \
((const struct temp_stm32_config*)(dev)->config->config_info)
#define DEV_DATA(dev) ((struct temp_stm32_data *)(dev)->driver_data)

/*
* HACK: absent a better way to learn the analog voltage reference on
* the board we are running on, hard-code V_REF+ to 3.3V, and assume
* V_REF- = 0V.
*/
#define VREF_MILLIVOLTS 3300
#define VREF_VOLTS ((float)VREF_MILLIVOLTS / 1000.0f)

/*
* See STM32F401xD, STM32F401xE datasheet 6.3.21 and chip
* reference manual and ST RM0368 chapter 11.
*/
#define STM32F401_V25 0.76f /* volts */
#define STM32F401_AVG_SLOPE 0.0025f /* volts / (degree C) */

#define ADC_RESOLUTION_12BIT 0x00
#define ADC_TO_VOLTS(adc_val) ((float)(adc_val) * VREF_VOLTS / 4095.0f)
#define ADC_PRESCALER_PCLK_DIV_8 0x03
#define ADC_SAMPLE_480_CYCLES 0x07
#define ADC_ONE_CONVERSION 0x00

/* This is valid for STM32F401x. */
#define ADC_TEMP_CHANNEL 18
#define ADC_TEMP_SMPR(adc) (adc)->SMPR1
#define ADC_TEMP_SMPR_SMP ADC_SMPR1_SMP18
#define ADC_TEMP_SMPR_POS ADC_SMPR1_SMP18_Pos

static int temp_stm32f401x_sample_fetch(struct device *dev,
enum sensor_channel chan)
{
const struct temp_stm32_config *cfg = DEV_CFG(dev);
ADC_TypeDef *adc = cfg->adc;
u32_t tmp;

__ASSERT(cfg->adc_channel == ADC_TEMP_CHANNEL,
"Expected temperature sensor channel %d", ADC_TEMP_CHANNEL);

/*
* Configure ADC for polled conversion of temperature sensor.
*
* TODO: this configuration could be improved (timing, etc.).
*/

/*
* CR1:
*
* - 12 bit resolution (the maximum).
*
* - Software initiated, polled conversion only (no
* interrupts, injected groups, scan mode, etc.).
*/

tmp = adc->CR1;
tmp &= ~(ADC_CR1_RES | ADC_CR1_JDISCEN | ADC_CR1_DISCEN |
ADC_CR1_JAUTO | ADC_CR1_SCAN | ADC_CR1_JEOCIE |
ADC_CR1_AWDIE | ADC_CR1_EOCIE);
tmp |= (ADC_RESOLUTION_12BIT << ADC_CR1_RES_Pos);
adc->CR1 = tmp;

/*
* CR2:
*
* - Software initiated, polled conversion of a single channel
* only (no external triggers, DMA, continuous conversion).
*
* - Right-aligned data in DR.
*
* - EOC bit in SR should be set at end of conversion.
*/

adc->CR2 &= ~(ADC_CR2_EXTEN | ADC_CR2_JEXTEN | ADC_CR2_ALIGN |
ADC_CR2_EOCS | ADC_CR2_DDS | ADC_CR2_DMA |
ADC_CR2_CONT);

/*
* SMPR:
*
* Temperature sensor sample time is 480 ADC cycles (the
* maximum).
*/

tmp = ADC_TEMP_SMPR(adc);
tmp &= ~ADC_TEMP_SMPR_SMP;
tmp |= (ADC_SAMPLE_480_CYCLES << ADC_TEMP_SMPR_POS);
ADC_TEMP_SMPR(adc) = tmp;

/*
* SQRx: Convert channel. One channel is being converted.
*/

tmp = adc->SQR3;
tmp &= ~ADC_SQR3_SQ1;
tmp |= (ADC_TEMP_CHANNEL << ADC_SQR3_SQ1_Pos);
adc->SQR3 = tmp;

tmp = adc->SQR1;
tmp &= ~ADC_SQR1_L;
tmp |= (ADC_ONE_CONVERSION << ADC_SQR1_L_Pos);
adc->SQR1 = tmp;

/*
* Start the ADC conversion, and wait for it to complete.
*/

adc->SR = ~(ADC_SR_EOC | ADC_SR_STRT);
adc->CR2 |= ADC_CR2_SWSTART;

do {
} while (!(adc->SR & ADC_SR_EOC));
adc->SR = ~(ADC_SR_EOC | ADC_SR_STRT);

return 0;
}

/* TODO */
static inline float stm32f401x_temp_c(float v_sense)
{
/*
* The voltage read by the temperature sensor, v_sense, is a
* linear function of the temperature. The point-slope form of
* the line is:
*
* (Temperature - 25.0°C) * Avg_Slope = v_sense - V_25
*
* Where V_25 is the measured voltage at 25°C, and Avg_Slope
* is the slope of the line in V/°C.
*
* Use this formula to convert the voltage to a
* temperature. See ST RM0368 11.9 and the chip datasheet for
* more details.
*/
return ((v_sense - STM32F401_V25) / STM32F401_AVG_SLOPE + 25.0f);
}

static int temp_stm32f401x_channel_get(struct device *dev,
enum sensor_channel chan,
struct sensor_value *val)
{
val->val1 = 0;
const struct temp_stm32_config *cfg = DEV_CFG(dev);
ADC_TypeDef *adc = cfg->adc;
u32_t adc_dr = adc->DR;
float v_sense = ADC_TO_VOLTS(adc_dr);
float deg_c = stm32f401x_temp_c(v_sense);

/* TODO fractional part */
val->val1 = (int32_t)deg_c;
val->val2 = 0;
return 0;
}
Expand All @@ -40,12 +184,59 @@ static const struct sensor_driver_api temp_stm32f401x_driver_api = {
.channel_get = temp_stm32f401x_channel_get,
};

/* TODO */
static inline void __temp_stm32f401x_get_clock(struct device *dev)
{
struct temp_stm32_data *data = DEV_DATA(dev);
struct device *clk = device_get_binding(STM32_CLOCK_CONTROL_NAME);

__ASSERT_NO_MSG(clk);
data->clock = clk;
}

static int temp_stm32f401x_init(struct device *dev)
{
const struct temp_stm32_config *cfg = DEV_CFG(dev);
struct temp_stm32_data *data = DEV_DATA(dev);
ADC_TypeDef *adc = cfg->adc;
ADC_Common_TypeDef *adc_common = cfg->adc_common;
u32_t tmp;

/* Turn on digital clock. */
__temp_stm32f401x_get_clock(dev);
clock_control_on(data->clock,
(clock_control_subsys_t*)&cfg->pclken);

/* Turn on ADC. */
adc->CR2 |= ADC_CR2_ADON;

/* ADC configuration for temperature sensor.
*
* - ADC clock prescaler to slowest possible (HACK) to avoid
* reading data sheets to figure out fastest possible.
*
* - Select temperature sensor, deselect VBAT (they are
* mutually exclusive, and VBAT has precedence).
*/
tmp = adc_common->CCR;
tmp &= ~(ADC_CCR_VBATE | ADC_CCR_ADCPRE);
tmp |= ((ADC_PRESCALER_PCLK_DIV_8 << ADC_CCR_ADCPRE_Pos) |
ADC_CCR_TSVREFE);
adc_common->CCR = tmp;

return 0;
}

static struct temp_stm32_config temp_stm32f401x_config = {
.adc = ADC1,
.adc_common = ADC,
.adc_channel = ADC_TEMP_CHANNEL,
.pclken = { .bus = STM32_CLOCK_BUS_APB2,
.enr = LL_APB2_GRP1_PERIPH_ADC1 },
};

static struct temp_stm32_data temp_stm32f401x_data;

DEVICE_AND_API_INIT(temp_stm32f401x, CONFIG_TEMP_STM32F401X_NAME,
temp_stm32f401x_init, NULL, NULL, POST_KERNEL,
temp_stm32f401x_init, &temp_stm32f401x_data,
&temp_stm32f401x_config, POST_KERNEL,
CONFIG_SENSOR_INIT_PRIORITY, &temp_stm32f401x_driver_api);

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