Digilent Pmod CMPS2 Referenzhandbuch - Seite 7

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Pmod CMPS2™ Reference Manual

I2CReadMultiple(6); //read six bytes, sending an ACK to the slave device betwe

en each byte received and a NACK after the last byte

20. Convert the readings into usable data. More details are available in the Data Conversion section.

21. Wait 1/3 of the acquisition time (by default 2.64 ms) before performing another measurement.

2.4

Applications Information

The Pmod CMPS2 is an ideal Pmod to use as a compass. Like all compasses, it is recommended that the Pmod

CMPS2 is calibrated before using the module.

To calibrate the magnetometer, the offset associated with the magnetic sensors and the environment needs to be

calculated and removed from future measurements.

The internal offset can be calculated and accounted for through the following method:

1. Power on the Pmod CMPS2 and wait for 10 mS before further operation.

2. Provide a START condition and call the device ID with a write bit

I2CBegin(0xA0); //device ID 0x30 with a write (0) bit

3. Wait to receive an ACK from the Pmod CMPS2.

4. Send the Internal Control Register 0 (address 0x07) as the register to communicate with

I2CWrite(0x07); //address 0x07 corresponds to Control Register 0

5. Wait to receive an ACK from the Pmod CMPS2.

6. Write the command to recharge the capacitor to prepare for the SET action.

I2CWrite(0x80); //0x80 refills the capacitor

7. Wait to receive an ACK from the Pmod CMPS2.

8. Delay at least 50 mS to allow the Pmod CMPS2 to finish preparing.

9. Provide a START condition and call the device ID with a write bit

I2CBegin(0xA0); //device ID 0x30 with a write (0) bit

10. Wait to receive an ACK from the Pmod CMPS2.

11. Send the Internal Control Register 0 (address 0x07) as the register to communicate with

I2CWrite(0x07); //address 0x07 corresponds to Control Register 0

12. Wait to receive an ACK from the Pmod CMPS2.

13. Write the command to start a SET action.

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