mirror of
https://github.com/zephyrproject-rtos/zephyr
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f05cbb421d
Correct handling of device encoded temperature values, which combine a 12-bit 2s complement signed value with a separate sign bit. Rework conversion between device and sensor temperature representations to support negative temperatures in both domains. Use a much simpler trigger configuration where the alert is driven by comparator output, rather than as an interrupt that requires a pair of I2C transactions to read and clear the flag. Refactor the trigger infrastructure to use the setup/handle/process idiom, which reduces duplicated code and to correctly detect alerts present when the triggers are set. Completely replace the sample with something that demonstrates updating upper and lower threshold values to track moving temperatures. Signed-off-by: Peter A. Bigot <pab@pabigot.com>
135 lines
3.6 KiB
C
135 lines
3.6 KiB
C
/*
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* Copyright (c) 2019 Peter Bigot Consulting, LLC
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* Copyright (c) 2016 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef ZEPHYR_DRIVERS_SENSOR_MCP9808_MCP9808_H_
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#define ZEPHYR_DRIVERS_SENSOR_MCP9808_MCP9808_H_
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#include <errno.h>
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#include <zephyr/types.h>
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#include <device.h>
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#include <drivers/sensor.h>
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#include <sys/util.h>
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#include <drivers/gpio.h>
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#define MCP9808_REG_CONFIG 0x01
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#define MCP9808_REG_UPPER_LIMIT 0x02
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#define MCP9808_REG_LOWER_LIMIT 0x03
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#define MCP9808_REG_CRITICAL 0x04
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#define MCP9808_REG_TEMP_AMB 0x05
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/* 16 bits control configuration and state.
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*
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* * Bit 0 controls alert signal output mode
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* * Bit 1 controls interrupt polarity
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* * Bit 2 disables upper and lower threshold checking
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* * Bit 3 enables alert signal output
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* * Bit 4 records alert status
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* * Bit 5 records interrupt status
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* * Bit 6 locks the upper/lower window registers
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* * Bit 7 locks the critical register
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* * Bit 8 enters shutdown mode
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* * Bits 9-10 control threshold hysteresis
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*/
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#define MCP9808_CFG_ALERT_MODE_INT BIT(0)
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#define MCP9808_CFG_ALERT_ENA BIT(3)
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#define MCP9808_CFG_ALERT_STATE BIT(4)
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#define MCP9808_CFG_INT_CLEAR BIT(5)
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/* 16 bits are used for temperature and state encoding:
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* * Bits 0..11 encode the temperature in a 2s complement signed value
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* in Celsius with 1/16 Cel resolution
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* * Bit 12 is set to indicate a negative temperature
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* * Bit 13 is set to indicate a temperature below the lower threshold
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* * Bit 14 is set to indicate a temperature above the upper threshold
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* * Bit 15 is set to indicate a temperature above the critical threshold
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*/
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#define MCP9808_TEMP_SCALE_CEL 16 /* signed */
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#define MCP9808_TEMP_SIGN_BIT BIT(12)
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#define MCP9808_TEMP_ABS_MASK ((u16_t)(MCP9808_TEMP_SIGN_BIT - 1U))
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#define MCP9808_TEMP_LWR_BIT BIT(13)
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#define MCP9808_TEMP_UPR_BIT BIT(14)
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#define MCP9808_TEMP_CRT_BIT BIT(15)
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struct mcp9808_data {
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struct device *i2c_master;
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u16_t reg_val;
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#ifdef CONFIG_MCP9808_TRIGGER
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struct device *alert_gpio;
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struct gpio_callback alert_cb;
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struct device *dev;
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struct sensor_trigger trig;
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sensor_trigger_handler_t trigger_handler;
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#endif
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#ifdef CONFIG_MCP9808_TRIGGER_OWN_THREAD
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struct k_sem sem;
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#endif
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#ifdef CONFIG_MCP9808_TRIGGER_GLOBAL_THREAD
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struct k_work work;
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#endif
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};
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struct mcp9808_config {
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const char *i2c_bus;
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u16_t i2c_addr;
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#ifdef CONFIG_MCP9808_TRIGGER
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u8_t alert_pin;
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u8_t alert_flags;
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const char *alert_controller;
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#endif /* CONFIG_MCP9808_TRIGGER */
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};
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int mcp9808_reg_read(struct device *dev, u8_t reg, u16_t *val);
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#ifdef CONFIG_MCP9808_TRIGGER
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int mcp9808_attr_set(struct device *dev, enum sensor_channel chan,
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enum sensor_attribute attr,
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const struct sensor_value *val);
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int mcp9808_trigger_set(struct device *dev,
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const struct sensor_trigger *trig,
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sensor_trigger_handler_t handler);
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int mcp9808_setup_interrupt(struct device *dev);
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#endif /* CONFIG_MCP9808_TRIGGER */
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/* Encode a signed temperature in scaled Celsius to the format used in
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* register values.
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*/
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static inline u16_t mcp9808_temp_reg_from_signed(int temp)
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{
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/* Get the 12-bit 2s complement value */
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u16_t rv = temp & MCP9808_TEMP_ABS_MASK;
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if (temp < 0) {
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rv |= MCP9808_TEMP_SIGN_BIT;
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}
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return rv;
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}
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/* Decode a register temperature value to a signed temperature in
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* scaled Celsius.
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*/
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static inline int mcp9808_temp_signed_from_reg(u16_t reg)
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{
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int rv = reg & MCP9808_TEMP_ABS_MASK;
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if (reg & MCP9808_TEMP_SIGN_BIT) {
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/* Convert 12-bit 2s complement to signed negative
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* value.
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*/
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rv = -(1U + (rv ^ MCP9808_TEMP_ABS_MASK));
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}
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return rv;
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}
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#endif /* ZEPHYR_DRIVERS_SENSOR_MCP9808_MCP9808_H_ */
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