984302_en-US

Yes

Can't start MMA6900 accelerometer

Hi,

I'm using MMA6900KQ accelerometer and can't read acceleration data. I'm using SPI to read it.

First I'm trying to init accelerometer. Here commands which I send via SPI and answers on it:

1) MOSI: 0x1410; MISO: 0xEA00; (Command: Set pointer to Device Status Register; answer: Critical/Reset Exception Response)

2) MOSI: 0x2000; MISO: 0xF281; (Command: DEVSTAT register data read; answer: 2 errors (IDE and DEVRES)

3) MOSI: 0x140E; MISO: 0xEA00; (Command: Set pointer to DEVCTL register; answer: Critical/Reset Exception Response)

4) MOSI: 0x3020; MISO: 0xFA0E; (Command: Register data write, data: Clear Error; answer: Critical/Reset Exception Response)

5) MOSI: 0x1410; MISO: 0xEA00; (Command: Set pointer to Device Status Register; answer: Critical/Reset Exception Response)

6) MOSI: 0x2000; MISO: 0xF680; (Command: DEVSTAT register data read; answer: 1 error (IDE)

And after it I'm trying to read acceleration data. As answer I've got 0x2047 acceleration always.

Help me, please, how to deal with this problem?

Accelerometers

Re: Can't start MMA6900 accelerometer

Thank you very much, Tomas! It helped me!

Re: Can't start MMA6900 accelerometer

Hi Mikhail,

The sequence for clearing errors looks correct, but we recommend using the soft reset sequence immediately after a power on to prevent issues due with the OTP readout after a power on.

Could you try the sequence below?

MOSI Expected MISO

0x1410 0xEA00

0x2000 0xF601

0x140E 0xEA00 // Set CE bit

0x3020 0xFA0E

0x1410 0x0800 // Read DEVSTAT

0x2000 0x1000

0x140E 0x0800 // Soft Reset

0x3080 0x180E

0x34C0 0x180E

0x3040 0x180E

// Delay 5ms Minimum

0x1410 0xEA00

0x2000 0xF601

0x140E 0xEA00 // Set CE bit

0x3020 0xFA0E

0x1410 0x0800 // Read DEVSTAT

0x2000 0x1000

0x4000 0x3806 // Read X-Axis

0x8000 0x4802 // Read Y-Axis

0x4000 0x380C

0x8000 0x47FE

0x4000 0x280E

0x8000 0x57FC

0x4000 0x280E

0x8000 0x47FE

0x4000 0x280E

0x8000 0x57FC

I hope it helps!

Best regards,

Tomas