SPIRIT1 VCO autocalibrate errata

[kzkaram]

Posted on August 14, 2015 at 19:20

So if I want to hop to various frequencies I need to calibrate the VCO each time. That's fine and expected. The SPIRIT1 has a fantastic auto calibration time of only around 50us - one of the features that make it attractive relative to other contenders. EXCEPT you can't use auto calibrate because it fails every so often according to the errata sheet!!. So it may as well not be there. Instead you have to go through an onerous manual calibration process for each possible frequency you wish to use (store the values and then load them in from the MCU each time later on) and worse still you need to repeat this entire process if the temperature changes significantly (think outdoor devices) or at reasonably regular intervals in any case.

Someone please tell me I am wrong... or better still when will the next revision of the SPIRIT1 become available?

[Nickname4815_O]

Posted on August 24, 2015 at 15:21

Hello,

as reported by the errata sheet that is a safe way of calibrating the device.In the most cases, performing the VCO calibration using that procedure is acceptable.As mentioned in previous posts, the SDK GUI exports that calibration proc and it is also available in the SPIRIT1_Libraries provided with the SDK.There won't be a new revision for SPIRIT1.Regards,F.

[kzkaram]

Posted on August 25, 2015 at 01:39

I guess you guys may have been on holiday as I can now see a bunch of answers which I'm grateful for.

However.... what I am trying to ask here is: Is the autocalibrate function on the SPIRIT1 effectively pointless? In other words, if it cannot be trusted then is there ever any point to use it? Should this function be crossed out of the SPIRIT1 feature list or is there a situation where it can be used? I'm not complaining about not having procedures for performing the manual calibration. I already wrote these myself so I don't need the SDK code. My problem is that I forsee that when we use the device in an outdoor environment with significant temperature changes in one day then we will need to keep measuring temperature regularly and repeat the manual calibration process probably several times. And since we intend to hop across several frequencies (though not so often) then we still have to perform this for each frequency every time and also store the results and download to the SPIRIT1 for each hop. I have not sat down to calculate it yet but I'm thinking that this is going to waste a whole lot of time and power compared to the occasional autocalibrate. If you think there is a better way please let me know. So if not a bug fixed revision of SPIRIT1, are we looking at seeing a less buggy and less picky SPIRIT2 shortly ;) ?

[Philippe SIMONNET]

Hi,

In case this post/answer is still useful :

- automatic VCO calibration is NOT recommended / this is aim of errata sheet

- it is highly recommended to perform manual calibration - using Workaround procedure

- if not doing any VCO calibration there is risk there are some Tx or Rx failures

- if you plan to use several frequencies I recommend to perform "one sequence" of calibration using all frequencies you plan to use and store outcome of calibration in RAM table - if temperature is not changing (+/-5°C range) you can use VCO calibration table.

Regards

Philippe