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Hardware details
The board can be connected to the I2C bus which is available on testpads around the debug connector.
The compass chip is directly connected to the I2C bus. The gyroscopes have an analog output which is digitized using a 16-bit A/D converter ADS1115 from Texas Instruments.
Additional features which were planned but are not implemented yet: The board contains the footprint to add an additional MSP430 microcontroller from TI. It would be used to control the offset compensation features of the gyroscopes, read their internal temperature sensors and switch them off when not used. Latter can actually be done using a GPIO line which is available at a testpoint H-TP1516.
Board Pictures
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Top side: two gyroscopes from InvenSense and a voltage regulator |
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Bottom side: the digital compass chip, space for a MSP430 microcontroller, and two ADCs. |
Installation
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Make sure that the shield or the GPS connector can't cause short circuits. |
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Insert the board into the empty space under the GPS connector. It fits thightly. |
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Solder the I2C-Wires to the testpoints at the debug connector. Refer to I2C for the pinout. The white wire is used to control the power supply of the gyroscopes. It connects to H-TP1516, or directly to 3.3V if this functionality is not needed. Power can be stolen from the AUX-Switch or, in this case, from the decoupling capacitor of the accelerometer. This power source will be disabled when the device suspends. |
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Reassemble the phone and stuff the remaining wires into the hole. |
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That's it! |
