MIKROE 3D Hall 7 click is a very accurate, magnetic field sensing Click board™, used to measure the intensity of the magnetic field across three perpendicular axes. It is equipped with the AK09970N, a high sensitivity 3D magnetic sensor IC, from AsahiKASEI.
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MIKROE 3D Hall 7 click is a very accurate, magnetic field sensing Click board™, used to measure the intensity of the magnetic field across three perpendicular axes. It is equipped with the AK09970N, a high sensitivity 3D magnetic sensor IC, from AsahiKASEI. This IC has a separate Hall sensing element on each axis, which allows a very accurate and reliable measurement of the magnetic field intensity in a 3D space, offering a basis for accurate positional calculations. The AK09970N magnetic sensor IC offers two industry-standard interfaces: both I2C and SPI communication protocols are supported by this IC. This sensor IC also features a powerful programmable interrupt engine with configurable polarity, switch event, and more.
The features such as the support for the 16-bit data output, high sensitivity and wide measurement range all make this sensor a perfect choice for various IoT applications. The internal 16-bit ADC, voltage reference and signal processing units makes the Click board™ a very accurate spatial magnetic sensor, perfectly suited for the development of various position sensing applications, contactless knobs, encoders, switches, and potentiometers, or some other type of magnetic field measuring application, based on an accurate spatial sensing.
3D Hall 7 click carries the AK09970N, a low power 3D magnetic sensor, from AsahiKASEI (AKM). This sensor relies on a Hall effect to accurately sense magnetic field changes on three perpendicular axes. The internal magnetic field sensing elements are multiplexed and connected to a pre-amplifier and then to a 16bit low noise Analogue to Digital Converter (ADC), which sequentially samples each sensor, providing 16-bit spatial data over the digital interface.
The magnetic sensor has a very low pin count. Therefore, SPI and I2C lines are multiplexed on the same pins. In order to allow functionality for both SPI and I2C interfaces, 3D Hall 7 click have onboard jumpers for communication interface selection. Thus, the communication interface selection procedure relies on switching the appropriate SMD jumpers, named COMM SEL. Note that all of the I2C/SPI group jumpers need to be switched at the same side: all three should either be soldered as I2C or SPI. If one of them shows in the opposite position from the rest, the communication with the IC might not be possible.
The power consumption is a big concern as of lately, with the introduction of the IoT. The ability to work in a low power mode is a must for every device which is to be used for any type of IoT networking. The AK09970N magnetic sensor features power down mode, single measurement mode and seven continuous measurement modes, allowing the user to make a perfect balance between sampling frequency, measurement accuracy and power consumption. The power consumption is in a close relationship with the data output refresh rate (ODR).
The AK09970N magnetic sensor also features a powerful programmable interrupt engine, which allows many event sources to be signalled via the two interrupt pins (INT and ODINT), which are routed from the sensor to the mikroBUS™ INT and AN pins respectively. A very useful function of the interrupt engine is the signalling of the data ready event. That way, the host MCU does not have to poll the sensor for the data acquisition. The sensor can simply trigger an interrupt when the data is ready for reading. The interrupt engine allows some other customizations of the interrupt signal, such as the magnetic sensor overflow, ADC overflow and Switch event.
The sensor provides raw data output, based on a strength of the magnetic field. The measurement is affected by many factors: slight manufacturing differences between ICs affect the readings, even the slight differences between Hall plates within the same IC might affect the accuracy, although the IC contains highly matched sensing elements. Also, the altitude might affect the readings, as well as temperature changes. Therefore, the IC is equipped with the temperature independent reference voltage, thus minimising the influence the mentioned unwanted factors.
The power mode, output data rate, interrupt thresholds for each axis, and other working parameters, including the availability of the I2C interface, are contained within the configuration registers of the AK09970N magnetic sensor. The sensor is highly configurable, with many configuration options. The AK09970N datasheet contains an in-depth explanation of all the registers and their functionality. However, 3D Hall 7 software library contains simplified functions that allow straight-forward readings to be performed, reducing the steps needed for a proper initialisation and configuration of the device.
The Click board™ can operate with 3.3V MCUs only, it is set to work over the I2C by default, and it is already equipped with the pull-up resistors. It is ready to be used as soon as it is inserted into a mikroBUS™ socket of the development system.