How to minimize the time required for a RX warmup on a Kinetis KW41Z?

[lukaskrupp]

Hello, I would like to know if there is any information on how to minimize the time required for a RX warmup between 2 RX sequences on a Kinetis KW41Z. Could this be done by disabling AuxPLL Frequency Calibration and DC Offset Correction? Are there any known values of warmup times which where already reached in the past?

[mario_castaneda]

Hi Lukas,

Could you please be more specific? what do you want to do? What do you mean by warm-up?

The time from a command being written to the GENFSK command register to the time when bits can be received by the PHY?

Or do they mean the mode change and startup time overall?  

Mode change time might have some opportunities for improvement as it is a software-driven time. The time from writing an RX_START_NOW command into SEQCMD field of the GENFSK->XCVR_CTRL register is a hardware determined the time for any type of RX and should be around 105usec. 

Internally, you could look at ANTGENRX and GENSTATE DTEST pages on external pins to see the ANT/GENFSK RX and state machine signals. You can look at RXWARMUP page to see the complete receive warmup time from LDO regulator startup to rx_init signal (almost the end of warmup).

The TSM timing for RX warmup is pretty much fixed by the hardware requirements and not open to changes. You should look at the software layers that are being wrapped around the GENFSK to see how much overhead they are adding.  Set a GPIO when the app layer asks for RX, then another GPIO when the RX_START_NOW sequence command is written into the register and finally observe one of the DTEST signals showing the end of RX warmup. This will give you a complete picture.

Best Regards,

Mario

[lukaskrupp]

Hello Mario,

thank you for your answer and the information. I was already able to eliminate all the overhead added by software. My problem is that I need a really fast transition between two RX ON phases (a complete RX sequence consists of a 105 us warmup, the ON phase and the 1 or 2 us warmdown according to the reference manual). I would like to have an enlarged RX sequence comprised of one RX warmup at the beginning, several ON phases and one warmdown at the end i.e. I somehow have to eliminate or shorten the warmup time of the ON phases in the middle of my RX sequence.

Is it possible to achieve this by using LPPS mode in which you can recycle back to any point in the RX warmup after complete packet reception?

Best regards,

Lukas