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API Description

/*
 * Author: Jon Trulson <jtrulson@ics.com>
 * Copyright (c) 2016 Intel Corporation.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <upm_utilities.h>
#include <otp538u.h>
bool shouldRun = true;
// analog voltage, usually 3.3 or 5.0
#define OTP538U_AREF   5.0
void sig_handler(int signo)
{
    if (signo == SIGINT)
        shouldRun = false;
}
int main()
{
    signal(SIGINT, sig_handler);
    // Instantiate a OTP538U on analog pins A0 and A1
    // A0 is used for the Ambient Temperature and A1 is used for the
    // Object temperature.
    otp538u_context temps = otp538u_init(0, 1, OTP538U_AREF);
    // enable debugging if you would like
    // otp538u_set_debug(temps, true);
    // Output ambient and object temperatures
    while (shouldRun)
    {
        float ambient = 0, object = 0;
        if (otp538u_get_ambient_temperature(temps, &ambient))
            printf("otp538u_get_ambient_temperature() failed\n");
        else if (otp538u_get_object_temperature(temps, &object))
            printf("otp538u_get_object_temperature() failed\n");
        else
            printf("Ambient temp: %f C, Object temp: %f C\n",
                   ambient, object);
        printf("\n");
        upm_delay(1);
    }
    printf("Exiting\n");
    otp538u_close(temps);
    return 0;
}

Go to the source code of this file.

Data Structures
struct	_otp538u_context

Functions
otp538u_context	otp538u_init (int pinA, int pinO, float aref)

void	otp538u_close (otp538u_context dev)

upm_result_t	otp538u_get_ambient_temperature (const otp538u_context dev, float *temperature)

upm_result_t	otp538u_get_object_temperature (const otp538u_context dev, float *temperature)

void	otp538u_set_voltage_offset (const otp538u_context dev, float offset)

void	otp538u_set_output_resistence (const otp538u_context dev, int resistance)

void	otp538u_set_ivref (const otp538u_context dev, float vref)

void	otp538u_set_debug (const otp538u_context dev, bool enable)

Typedefs
typedef struct _otp538u_context *	otp538u_context

Function Documentation

otp538u_context otp538u_init	(	int	pinA,
		int	pinO,
		float	aref
	)

OTP538U constructor

Parameters

pinA	Analog pin to use for the ambient temperature
pinO	Analog pin to use for the object temperature
aref	Analog reference voltage

Returns: intialized context, or NULL if error

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void otp538u_close ( otp538u_context dev )

OTP538U destructor

Parameters

dev	Device context

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upm_result_t otp538u_get_ambient_temperature	(	const otp538u_context	dev,
		float *	temperature
	)

Gets the ambient temperature in Celsius

Parameters

dev	Device context
temp	Ambient temperature

Returns: UPM status

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upm_result_t otp538u_get_object_temperature	(	const otp538u_context	dev,
		float *	temperature
	)

Gets the object temperature in Celsius

Parameters

dev	Device context
temp	Object temperature

Returns: UPM status

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void otp538u_set_voltage_offset	(	const otp538u_context	dev,
		float	offset
	)

Sets the offset voltage

The Seeed Studio wiki gives an example of calibrating the sensor and calculating the offset voltage to apply. Currently, the default value is set, but you can use the function to set one of your own.

Parameters

dev	Device context
vOffset	Desired offset voltage

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void otp538u_set_output_resistence	(	const otp538u_context	dev,
		int	resistance
	)

Sets the output resistance value

The Seeed Studio wiki example uses a value of 2,000,000 in one of the equations used to calculate voltage. The value is the resistance of a resistor they use in the output stage of their SIG2 output. This was 'decoded' by looking at the EAGLE* files containing their schematics for this device.

Parameters

dev	Device context
outResistance	Value of the output resistor; default is 2M Ohm

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void otp538u_set_ivref	(	const otp538u_context	dev,
		float	vref
	)

Sets the reference voltage of the internal Seeed Studio voltage regulator on the sensor board.

The Seeed Studio wiki example uses a value of 2.5 in one of the equations used to calculate the resistance of the ambient thermistor. The value is the voltage of an internal voltage regulator used on the sensor board. This was 'decoded' by looking at the EAGLE files containing their schematics for this device.

Parameters