Regarding RawCount spike noise at CapSense Tuner(Asynchronized mode)

[YuMa_1534086]

Hello Cypress.

I sometimes see RawCount spike noise(about 250 counts) like attached PNG file at CapSense Tuner(Asynchronized mode).

Such spike noise does not occur in Synchronized mode.

Q1)

Spike noise seems to be occurred due to read RawCount(2byte) during updating(RawCount update is not complete).

For example, spike noise occurs when reading RawCount data at below timing.

===============================================

RawCount MSB was updated, but LSB was not updated yet(LSB is previous data)

Or

RawCount LSB was updated, but MSB was not updated yet(MSB is previous data)

===============================================

Is my understanding correct?

Attached file is log file of CapSense Tuner.

Q2)

If Q1 is yes, which will be updated first, MSB or LSB of CapSense data?

Is LSB updated first because Cortex M0 uses little-endian format?(LSB -> MSB?)

Or MSB first?(MSB -> LSB?)

Best Regards.

Yutaka Matsubara

[Hari · Accepted solution]

Hi YuMa_1534086​

The explanation for Q1 is correct. The random noise that you are observing is due to timing mismatch between the tuner reads and the CapSense processing. The data is read while it is being updated.

Q2)

-> The data is written with LSB updated first, that is, LSB->MSB

Thanks and regards

Hari

[YuMa_1534086]

Dear Hari-san.

Thank you for your response.

I understand.

Best Regards.

Matsubara / Macnica