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In the documentation for the CC1101 RF radio chip it is advised :
In order to ensure reliable operation, CC1101 includesfrequency synthesizer self-calibration circuitry.This calibration should be done regularly, andmust be performed after turning on power andbefore using a new frequency (or channel).
Currently I have the chip doing AUTOCAL avery time it comes out of IDLE mode into RX or TX mode. This is set-up using then MCSM0 register.
My question relates to the frequency of autocalibration that needs to be done, that is, how often really ? Is it necessary to do the calibration every time the chip transmits or receives ?? What is "should be done regularly" in milliseconds/seconds ??There is no advice in the documentation on how often it is required, other than what is stated in the above paragraph.
I do a calibration after turning on power, but I always use the same frequency of transmission and reception once the frequency is set-up at the start.
This self-PLL-calibration does take some time, and I'd rather not do it unless it is really required.
Refer to CC1101 RF Calibration - Optimal interval : http://e2e.ti.com/support/low_power_rf/f/155/t/16238.aspx
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In reply to RGW:
Thanks, I did come across that discussion, and according to Sverre, and I quote :
"The calibration is done to make the PLL lock to the programmed RF
frequency (i.e get the correct VCO current, VCO capacitance and charge
pump current). If there is no significant change in temperature (e.g
more than +/-20C) or supply voltage there is no need to do a
Not sure what you mean by "doing manual calibration to maximise RX
time". Doing an automatic calibration when going from IDLE to RX is
easier and you only have to issue one strobe command as opposed to two
if you do the calibration manually before putting the device into RX."
However, in our case, there is a significant change in temperature (say from 0 to 50 deg. Celsius), so I would like to do regular calibrations, but not every ms - that is overdoing it in my opinion.
There is a strobe command to perform a manual calibration, so NOT doing automatic calibration when changing from IDLE to RX is possible. Currently I do automatic calibration and it is too often as I do not have a choice other than every 12,178ms for instance.
It this case, where temperature variation is large and automatic calibration is NOT possible because the 800us delay to do it is significant enough to cause problems with existing code timing constraints.
What is the recommended or optimal, maximum period between calibrations during normal operation (0 to 50 Celsius) in TX / RX modes for the CC1101 chip radio, so that the sensitivity is optimal ??
In reply to citizen:
It is perfectly alright to do a manual calibration as opposed to automatic calibration. The automatic calibration does the IDLE - CALIBRATE - RX (say) transition automatically when SRX strobe is issued and AUTO CAL is enabled. Doing IDLE - SCAL - SRX (i.e manual calibration) with AUTO CAL disabled will give the same result.
If your temperature changes from 0C to 50C you can calibrate at 25C (say) and the PLL will still be in lock at the extreme temperatures. Still, I would recommend you calibrate at regular intervals. Once every 1 minute will be ok. Doing a calibration every 1 minute will not add much to the average current if you enter active mode every 12.178 ms.
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