CC1310: Relation between RAT RX timestamp and ClockP_timestamp() to calculate ClockP_setTimeout()?

Pieter Conradie

Part Number: CC1310

Hi there!

I'm using CCS 11.0.0.00012 and SimpleLink CC13x0 SDK 4.20.01.03 to develop a NoRTOS app for the CC1310.

In my case the received packet contains info when to expect the next beacon packet (up to 20 seconds later). I want to use the ClockP FW module to wake up a few milliseconds in advance, do some housekeeping, and start RX just in time to receive the beacon packet.

The received packet is timestamped by the RAT (4 MHz) but the ClockP module has a 100 kHz timebase. Both are using the RTC for synchronization(?).

Is there a way to convert the RAT timestamp into a ClockP timestamp so that I can calculate the appropriate delay for ClockP_setTimeout()?

Or should I rather save a ClockP timestamp when I get an RF_EventRxEntryDone event (which is cruder and not the most accurate)?

Thanks in advance,

Pieter

https://piconomix.com

over 3 years ago

0 Marie H over 3 years ago

TI__Guru* 81261 points

Hi Pieter,

If you were using an RTOS, you would not need to set up a separate clock for this. As long as your radio is aware of when to expect the next packet, the device would wake up in time to receive it.

Since you're using nortos, I'm not sure whether you do need to set up a separate clock. You can do a test without. (E.g. use Energy trace to see when the device is waking up.)

We have some advice about working with the RAT and the RTC in the RF driver documentation: https://dev.ti.com/tirex/explore/content/simplelink_cc13x0_sdk_4_20_01_03/docs/tidrivers/doxygen/html/_r_f_8h.html

See e.g. "Deferred dispatching of commands with absolute timing", and the following APIs: RF_getCurrentTime(), RF_convertRatTicksToMs etc.

Cheers,

Marie H

0 Pieter Conradie over 3 years ago in reply to Marie H

Prodigy 170 points

Hi Marie,

Apologies for the late reply. I had to try a few things first and it seems to be working now.

If I understand correctly, the RAT @ 4 MHz stops running when the RF core is powered down but it resynchronised with the RTC when the RF core is powered up again.

The ClockP module @ 100 kHz is also synchronised with the RTC.

All I had to do was take the RAT timestamp and divide it by 40 to convert it to a ClockP_getSystemTicks() value. Will this always work and is it a good solution?

EDIT / UPDATE:

So my two pseudo code options are:

uint32_t clockp_timestamp = rat_timestamp / 40;

or:

uint32_t clockp_timestamp = ClockP_getSystemTicks() - (RF_getCurrentTime() - rat_timestamp) / 40;

Thanks in advance,

Pieter

+1 Marie H over 3 years ago in reply to Pieter Conradie

TI__Guru* 81261 points

Hi Pieter,

Yes this sounds like a good solution.

If you search here on E2E you will find many threads on the topic of converting between RAT and RTC. E.g.:

https://e2e.ti.com/support/wireless-connectivity/sub-1-ghz-group/sub-1-ghz/f/sub-1-ghz-forum/935741/ccs-lpstk-cc1352r-implementing-timestamp-in-collector-ui/3457001?tisearch=e2e-sitesearch&keymatch=rat%25252525252520rtc%25252525252520timestamp#3457001

Cheers,

Marie H

Sub-1 GHz

Sub-1 GHz forum

CC1310: Relation between RAT RX timestamp and ClockP_timestamp() to calculate ClockP_setTimeout()?