Rasberry Pi, "PLL Not locked", do I need to worry?

[t...@quarendon.net]

When I run rtl_433 on my Pi, the output I get is

Found 1 device(s):

  0:  Realtek, RTL2838UHIDIR, SN: 00000001

Using device 0: Generic RTL2832U OEM

Detached kernel driver

Found Rafael Micro R820T tuner

Exact sample rate is: 250000.000414 Hz

[R82XX] PLL not locked!

Sample rate set to 250000.

Bit detection level set to 0.

Tuner gain set to 35.000000 dB.

Reading samples in async mode...

Tuned to 433500000 Hz.

Do I need to worry about the "PLL not locked" message?

With the -a option on, I do get output, but I'm looking for reasons why I'm not getting anything decoded (I get -a output, but nothing every gets decoded).

[Benjamin Larsson]

Hi,

On 04/10/2016 09:24 AM, t...@quarendon.net wrote:
> When I run rtl_433 on my Pi, the output I get is
>
> Found 1 device(s):
> 0: Realtek, RTL2838UHIDIR, SN: 00000001
>
> Using device 0: Generic RTL2832U OEM
> Detached kernel driver
> Found Rafael Micro R820T tuner
> Exact sample rate is: 250000.000414 Hz
> [R82XX] PLL not locked!
> Sample rate set to 250000.
> Bit detection level set to 0.
> Tuner gain set to 35.000000 dB.
> Reading samples in async mode...
> Tuned to 433500000 Hz.
>
>
> Do I need to worry about the "PLL not locked" message?

This is from librtlsdr:

https://github.com/librtlsdr/librtlsdr/blob/master/src/tuner_r82xx.c#L550

Do you get this every time or only once ?

>
> With the -a option on, I do get output, but I'm looking for reasons why
> I'm not getting anything decoded (I get -a output, but nothing every
> gets decoded).

If the PLL doesn't lock the output can't be trusted. Take the device to
your computer and run it there to ensure that it works.

MvH
Benjamin Larsson

[t...@quarendon.net]

Do you get this every time or only once ?

I get this every time I run when running on the raspberry pi.

Running with the same dongle plugged into my windows machine I don't get the message.

Not sure what you mean by taking my device to the computer and running it there. Do you mean putting the transmitter next to the aerial? 

I've tried all sorts of things to get a successful reading of something, with a couple of different devices, and the same dongle plugged into either a windows PC, or a raspberry pi, but no far I've yet to decode any kind of signal to something readable.

Any help would be appreciated!

Thanks.

[Benjamin Larsson]

Try running the dongle under linux. I have no idea why it doesn't work
under windows.

MvH
Benjamin Larsson

[t...@quarendon.net]

Try running the dongle under linux. I have no idea why it doesn't work
under windows.

No, I AM running it under Linux, on a Raspberry Pi. 

It works fine under Windows, but not under linux on the pi. It always gives me a "PLL not locked" message. 

[Benjamin Larsson]

I got that. I just meant that you should try running the rtl-sdr dongle
on some platform to verify that the hardware is ok. It it possible that
the RPi is not suitable for running your dongle.

MvH
Benjamin Larsson

[t...@quarendon.net]

I have no other platform.

I'm going to have to hack the rtl_sdr code to see whether this is just a spurious message from tuning to another frequency, or whether it is actually failing to tune to the desired frequency.

The post here: https://www.reddit.com/r/RTLSDR/comments/3fjk35/what_is_r82xx_pll_not_locked/ seems to suggest you could get these spuriously.

So far that bit is unclear.

[Iluta V]

Dear Tom,

I have the same "PLL not locked" message for rtl dongle while running on Ubuntu 14.04, and that far I haven't been able to find a solution on internet how to fix that.

So very likely it is rtl problem and not connected to a specific platform.

Rtl does RX and I'm not sure if it doen't drop packets / samples because of "PLL not locked" message, so I use HackRF  mostly instead.

Please let me know if you find a solution to fix it.

Sincerely,

Iluta

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[t...@quarendon.net]

I suspect that this is spurious output.

If I modify the rtl-sdr code, I get output like this:

Found Rafael Micro R820T tuner

[R82XX] PLL locked to freq 56000khz!

Exact sample rate is: 250000.000414 Hz

[R82XX] PLL not locked to freq 2125khz!

Sample rate set to 250000.

Bit detection level set to 0.

Tuner gain set to 35.000000 dB.

Reading samples in async mode...

[R82XX] PLL locked to freq 436045khz!

Tuned to 433920000 Hz.

So although it fails to lock at some point, it then subsequently does achieve a lock. I haven't delved too far into the logic to see why it's attempting locks at other frequencies, but on the face of it looks like this is a message that's safe to ignore.

I'll revisit this though if I get issues where I think it's not receiving as it should.

[t...@quarendon.net]

I can receive and decode valid signals from a Oregon temperature sensor, so I think this is working OK, despite the spurious message.

[Daryl Williams]

I get this all the time [R82XX] PLL not locked. On Linux Ubuntu 16.04

PLL stands for Phase Lock Loop which relates to a radio crystal oscillator locking a frequency. I remember this in my CB radio/Amateur radio days.

The way I look at it. If I'm getting pulse data, I'm happy.

 I'm using a cheap TV dongle. Cheap meaning you can't expect to have a PLL in the dongle. Because if it had PLL circuitry with crystals it would cost a lot more.

What you pay is what you get. But boy am I having fun with this dongle.

I wouldn't worry about it.

[Benjamin Larsson]

On 08/01/2016 03:22 PM, Daryl Williams wrote:

> I'm using a cheap TV dongle. Cheap meaning you can't expect to have a
> PLL in the dongle. Because if it had PLL circuitry with crystals it
> would cost a lot more.
>

For the record, the R820T tuner chip has a PLL.

MvH
Benjamin Larsson

[Daryl Williams]

[BLUSHING] - I stand corrected... Even though I'm sitting down.

[Alex Knuckles]

You guys probably aren't making the mistake but I saw the same error on my Pi. If I used decimals in the frequency argument like I use for rtl_fm (-f 343.966.000M) I got the "PLL not locked!" error, if I took the decimals out (-f 343966000) I didn't get it.