CC1200: Lower data jitter in Transparent mode...

- Why do you only need 1 m range?

- Why do you want very small jitter? The recommended is to let the MCU do oversampling on the received signal to avoid the effect of the jitter

Hello Ghost...

Thanks for the reply...

The 1 meter of range is because the devices ( more than 1 device syncing with a single sync source ) are near when performing sync operations...

However, I can not enter in the details of the operations, it would be too complex, but this is what I need... And I want to evaluate the timings to see if it will fit the sync requirementes... If my calcuations are ok, that will fit...

Regards

Alex

Hi Alex,

Are you planning on using FSK or OOK modulation? What data rate are you planning on using?

Hi Diego,

tnx for the reply...

In my application, the sync phase is used to permit few  'client' timers to measure a 'host' timer period through RF pulses, so, no micro interaction with trasmitted data in this phase, only timers triggering on RF data pulses, the micro will stand aside and then use timers measurements...

Datarate will be up to the most I can get to have the higher time resolution in this phase and condition ( very short devices separation ), and that's why I am considering the cc1200, having it higher data rates and trasparent mode...

In transparent mode the host timer will emit long pulses as asyncronous TX data, the client timers would sync on the falling edge of such pulses with a capture... Also, for modulation to use, I am still not sure, I will check which one would give me better results, even if I think that syncing on the falling edge (end of the period) of a pulse may work fine also with 2/4GFSK...

So, that's why the expected jittering measure is the most important factor for me...

Kind regards

Alex

Hi Alex,

If I understand correctly you want to use a RF pulses from a 'host' to synchronize the timers in multiple 'client' devices?

How long is the pulse and would it only be one pulse or multiple pulses?

Transparent mode only supports 2'ary modulation formats. In the case of GFSK that would mean only 2-GFSK.

Hi Diego,

You understood correctly, or better, to let the cliets also to measure with a certain precision the period of the 'Host' timer...

How many or duration is not important, it may last seconds, I will decide based on the precision I need in the application, I already have done this with other RF devices ( analog ), I need just to get the possible lowest jitter on the outputted data in transparent mode...

if I know that the sampling resolution in the data output amounts to some delta time, I know that I will have such precision in the measure, precision that of course on a measure of one second has a meaning, but on a measure of 10 seconds period has another...

2GFSK would be good...

So, my question is simple, are my expectations, based on the CC1200 User guide, correct...? Did I misunderstood anything...?

Thanks

Alex

The UserGuide state "The rate on the GPIO is ((4 x receiver bandwidth) x interpolation factor). " meaning that the jitter will be less than what you calculate here, at least less than 1/8 of the rate. But not sure how well transparent mode will work with zero IF and wide open RX filter but most likely good enough for 1 m range. 

Hello,

well, thanks to all of you for the infos and confirmation...

I just sent away the schematics and will eventually tell you about my results once I start to work on it ( and with present chips shortages, I hope, within this year... )...

Regards

Alex