ab135622cf
The TMP105 datasheet says that in Interrupt Mode (when TM==1) the device signals an alert when the temperature equals or exceeds the T_high value and then remains high until a device register is read or the device responds to the SMBUS Alert Response address, or the device is put into Shutdown Mode. Thereafter the Alert pin will only be re-signalled when temperature falls below T_low; alert can then be cleared in the same set of ways, and the device returns to its initial "alert when temperature goes above T_high" mode. (If this textual description is confusing, see figure 3 in the TI datasheet at https://www.ti.com/lit/gpn/tmp105 .) We were misimplementing this as a simple "always alert if temperature is above T_high or below T_low" condition, which gives a spurious alert on startup if using the "T_high = 80 degrees C, T_low = 75 degrees C" reset limit values. Implement the correct (hysteresis) behaviour by tracking whether we are currently looking for the temperature to rise over T_high or for it to fall below T_low. Our implementation of the comparator mode (TM==0) wasn't wrong, but rephrase it to match the way that interrupt mode is now handled for clarity. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Cédric Le Goater <clg@kaod.org> Message-id: 20201110150023.25533-3-peter.maydell@linaro.org
56 lines
1.3 KiB
C
56 lines
1.3 KiB
C
/*
|
|
* Texas Instruments TMP105 Temperature Sensor
|
|
*
|
|
* Browse the data sheet:
|
|
*
|
|
* http://www.ti.com/lit/gpn/tmp105
|
|
*
|
|
* Copyright (C) 2012 Alex Horn <alex.horn@cs.ox.ac.uk>
|
|
* Copyright (C) 2008-2012 Andrzej Zaborowski <balrogg@gmail.com>
|
|
*
|
|
* This work is licensed under the terms of the GNU GPL, version 2 or
|
|
* later. See the COPYING file in the top-level directory.
|
|
*/
|
|
#ifndef QEMU_TMP105_H
|
|
#define QEMU_TMP105_H
|
|
|
|
#include "hw/i2c/i2c.h"
|
|
#include "hw/misc/tmp105_regs.h"
|
|
#include "qom/object.h"
|
|
|
|
#define TYPE_TMP105 "tmp105"
|
|
OBJECT_DECLARE_SIMPLE_TYPE(TMP105State, TMP105)
|
|
|
|
/**
|
|
* TMP105State:
|
|
* @config: Bits 5 and 6 (value 32 and 64) determine the precision of the
|
|
* temperature. See Table 8 in the data sheet.
|
|
*
|
|
* @see_also: http://www.ti.com/lit/gpn/tmp105
|
|
*/
|
|
struct TMP105State {
|
|
/*< private >*/
|
|
I2CSlave i2c;
|
|
/*< public >*/
|
|
|
|
uint8_t len;
|
|
uint8_t buf[2];
|
|
qemu_irq pin;
|
|
|
|
uint8_t pointer;
|
|
uint8_t config;
|
|
int16_t temperature;
|
|
int16_t limit[2];
|
|
int faults;
|
|
uint8_t alarm;
|
|
/*
|
|
* The TMP105 initially looks for a temperature rising above T_high;
|
|
* once this is detected, the condition it looks for next is the
|
|
* temperature falling below T_low. This flag is false when initially
|
|
* looking for T_high, true when looking for T_low.
|
|
*/
|
|
bool detect_falling;
|
|
};
|
|
|
|
#endif
|