How to use GPIO5/6 as Switch reference in DWM1000

Wireless Connectivity Ultra-Wideband
, , ,
1

I need to add LNA to DWM1000 to extend the range.
However, when I use GPIO5 as EXTTXE and connect to the switch, it doesn’t work.
Unlike GPIO5, the GPIO6/EXTRXE works well.
I’m sure the control pins are right, and the waveform from EXTTXE and EXTRXE are complementary in oscilloscope. How’s that going?
Did someone do the same thing before?
Dennis

2

Hi Denis

First of all, could I ask you what range you actually get? I’m asking as sometimes customers just use an LNA to extend the range, because the range is disappointing for reasons like software and or hardware.

For example, for the best results when using the DWM1000 using our example API you will need to adjust the default transmit power value programmed into the DWM1000 in software by approximately 3 dB. This because the example code is geared towards the EVB1000 board (EVK1000 and TREK1000) which has a different RF path compared to the DWM1000.

Anyways, see (latest) APS014 Revision 1.4 in which it is explained that some code adjustments need to be applied.
https://www.decawave.com/application-notes/ (the doc can be found under Regulations and Certification) .

Other sources of information can be found in APS004 on increasing range and of ofcourse our DW1000 user manual and DWM1000 datasheet.

/Leo

3

Thank you, Leo, for the detailed explanation.
We finally find out some settings are not correct so that
there are some tiny gaps read by oscilloscope in EXTTXE.

Then, we fix the problem by setting correct code.
However, there is still one 1.5 ms gap in EXTRXE which we dont want.

By the way, the range we get is over 400 m by adding two switch and PA, LNA in the front end.
Also changing the channel into channel 1 and the DA/mixer to 15 dB.
but the range shows by DWM1000 will be negative over 327 m. (In the beginning, -328 m)
We use the range measured by DWM1000 and add 655 m to make it positive and over 327 m.

Is that right? or is there a correct number to be add for changing the range into positive?

Dennis

4

Hi Denis,
400m is quite some distance, Would you have tried to calibrate / fine tune the antenna delay? Having unreasonable values will give you unreasonable distances.
The range inaccuracy could possibly also be caused by clockdrift and the power you’re applying. Please se APS011, attached. APS011 Sources of error in TWR.pdf (961.7 KB)

5

How about just use gpio 6 to control ext PA and ext lna ? Is there any problem ？

6

Hi Leo,
We have calibrated the antenna delay by setting a reference range.
I guess the range measured by DWM1000 is designed to be below 300 m,
so the data would be wrong when the real range is over 327 m.
We’ll read APS011 to find out the solution, thank you!

7

It is OK to just use GPIO 6.
We just want to find out the reason of gaps and make sure the operation is fine.

8

Thanks a lot。 Is there any detailed design references for ext PA and lna ? where can I get?