Lime DVB Firmware

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M0PIT
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Joined: Fri Jun 07, 2019 8:12 pm

Lime DVB Firmware

Post by M0PIT » Mon Mar 30, 2020 3:11 pm

I’ve been trying out the new DVB firmware for the Lime mini and I’m experiencing a 25 second delay on the received signal on the Minitioune when streaming using IPTS. When using 1.30 Lime firmware I get about a 2.5 second delay.

Portsdown setyp:
Sym Rate 333
MOD DVB-S
FEC 7/8
FRQ 146.5
ENCODER IPTS

With such a long delay I’ve gone back to Lime version 1.30, has any seen this type of delay with the DVB firmware or is it finger problems on my part?

Phil
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G8GKQ
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Re: Lime DVB Firmware

Post by G8GKQ » Mon Mar 30, 2020 3:58 pm

Hi Phil

Thanks for pointing this out. I had not realised that the delay was so long for DVB-S. The delay for DVB-S2 (333 kS 9/10 FEC)is about 6 seconds, so a lot more acceptable, although still longer that the normal firmware (1.30) delay of 2 seconds.

The LimeDVB firmware was really intended to allow higher SRs on the LimeSDR Mini, and at the higher SRs the delay reduces (10 seconds on 1MS 7/8 FEC DVB-S).

So, you can either stick with Firmware 1.30, or switch to DVB-S2, or both. And it's not finger trouble - I have just reproduced the problem on my test rig.

I will look at whether I can reduce the delay for DVB-S (this might be in the code that I can edit). By coincidence, I e-mailed the author of the LimeDVB firmware this morning about whether there was any chance of reducing the extra delay (the 6 seconds vs 2 seconds for DVB-S2) that is in the really clever code that he has written.

Dave, G8GKQ

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Re: Lime DVB Firmware

Post by G8GKQ » Mon Mar 30, 2020 8:41 pm

Phil

I found some of the problem and have just issued a development release with a fix that reduces the delay that you reported from 25 seconds (unusable) to about 6 seconds (just usable). It only affects LimeDVB DVB-S transmissions, no others.

There is still about 4 seconds that I think can be pruned, but I think that is in the FPGA software, which is way beyond me, so I have asked Nats (who wrote that) to look at it.

If you want to try the development release, first update to the latest production version (202003280) and then try to update again. Press the "Dev Update" button.

Dave, G8GKQ

M0PIT
Posts: 13
Joined: Fri Jun 07, 2019 8:12 pm

Re: Lime DVB Firmware

Post by M0PIT » Tue Mar 31, 2020 2:48 pm

Hi Dave,

Thanks for the prompt response and action, now running the your development release.

Phil, M0PIT

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