BB amplifier does not work and make reception not work.

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fperal
Posts: 9
Joined: Tue Nov 26, 2013 3:13 am

BB amplifier does not work and make reception not work.

Post by fperal » Wed Apr 05, 2017 2:18 am

I have two bladeRF whose RX works faulty. They may have been used with RF gain different to 0.
I have been testing it taking measures wit oscilloscope and spectrum analizer at RXOUTI/RXOUTQ of LMS6002.

Both of them work with RX gain set to RF=0; IF=0, BB=0.
Both of them stop receiving if I set BB to something different to 0, and then they seem to be hanged, if I set again BB=0 the don't work until I unplug the bladeRF from the usb and I plug it in again.

For one of them the IF gain works for the other it doesn't (I can set IF to any value but still signal measured at RXOUT have the same amplitude).

Does it mean that BB amplifiers (i.e.: RXVGA2) are broken and when using BB=0 they are bypassed and that is why the blade works with bb=0?

regards

bglod
Posts: 45
Joined: Thu Jun 18, 2015 6:10 pm

Re: BB amplifier does not work and make reception not work.

Post by bglod » Wed Apr 05, 2017 9:49 am

If you can receive at all, it's unlikely the internal amplifiers are broken, but I suppose it's possible. Has your bladeRF been exposed to any signals above +23 dBm?

What frequency are you tuned to? Are you able to use standard software such as Gqrx to receive and tweak the gains?

If you're probing at J61, I assume you closed the RXOUT switch and are familiar with the circuitry (e.g. Figure 3.1 on page 26 of the LMS6002d Programming and Calibration Guide). There is a note in Table 4 to disable RXVGA2 if using the RXOUT port, but I believe that is only if you want to use it as an input.

fperal
Posts: 9
Joined: Tue Nov 26, 2013 3:13 am

Re: BB amplifier does not work and make reception not work.

Post by fperal » Wed Apr 05, 2017 11:35 am

bglod wrote:If you can receive at all, it's unlikely the internal amplifiers are broken, but I suppose it's possible. Has your bladeRF been exposed to any signals above +23 dBm?
It is possible. I didn't know you can not set RF gain, so I have used it with RF gain while receiving and it is posiible that a mobile phone where near the blade, so....... yes, maybe.


What frequency are you tuned to? Are you able to use standard software such as Gqrx to receive and tweak the gains?
433Mhz. I will try gqrx
I am using GRC with a diagram that works with other bladeRF


If you're probing at J61, I assume you closed the RXOUT switch and are familiar with the circuitry (e.g. Figure 3.1 on page 26 of the LMS6002d Programming and Calibration Guide). There is a note in Table 4 to disable RXVGA2 if using the RXOUT port, but I believe that is only if you want to use it as an input.
I have used the datasheet of LMS600s and the documentation of BladeRF schematics (page 11).
I am probing at J61 but I havent closed any switch. I assumed It must be closed as I can measure signal al J61 pins. I don't know how to manipulate this switch.

regards

bglod
Posts: 45
Joined: Thu Jun 18, 2015 6:10 pm

Re: BB amplifier does not work and make reception not work.

Post by bglod » Wed Apr 05, 2017 4:42 pm

If you can receive with Gqrx, see activity at various frequencies, and the gain settings have an effect, you should be fine. However, if the LMS was exposed to +23 dBm or higher signals, the front end could be blown out. I'm not sure what could be causing the hang though.

Interesting that you can probe it. Maybe it gets closed during initialization. Can you do a "bladeRF-cli -e peek lms 0x9" and see if bit 7 is a '0' (RXOUTSW open) or '1' (RXOUTSW closed)?

fperal
Posts: 9
Joined: Tue Nov 26, 2013 3:13 am

Re: BB amplifier does not work and make reception not work.

Post by fperal » Mon Apr 17, 2017 3:53 am

With gqrx works fine too

Code: Select all

administrador@PC1411:~$ bladeRF-cli -i peek lms 0x9
bladeRF> peek lms 0x09

  0x09: 0x40
    [7:7]       0 (0x00)      RXOUTSW                         
    [6:0]      64 (0x40)      CLK_EN[6:0]                     
    [6:6]       1 (0x01)      PLLCKLOUT CLK_EN                
    [5:5]       0 (0x00)      LPF_CAL CLK_EN                  
    [4:4]       0 (0x00)      RX VGA2 CLK_EN                  
    [3:3]       0 (0x00)      RX LPF CLK_EN                   
    [2:2]       0 (0x00)      RX DSM CLK_EN                   
    [1:1]       0 (0x00)      TX LPF CLK_EN                   
    [0:0]       0 (0x00)      TX DSM CLK_EN                   

bladeRF>
And I can robe at J61

but

Code: Select all

bladeRF> poke lms 0x09 0xC0

  0x09: 0xc0
    [7:7]       1 (0x01)      RXOUTSW                         
    [6:0]      64 (0x40)      CLK_EN[6:0]                     
    [6:6]       1 (0x01)      PLLCKLOUT CLK_EN                
    [5:5]       0 (0x00)      LPF_CAL CLK_EN                  
    [4:4]       0 (0x00)      RX VGA2 CLK_EN                  
    [3:3]       0 (0x00)      RX LPF CLK_EN                   
    [2:2]       0 (0x00)      RX DSM CLK_EN                   
    [1:1]       0 (0x00)      TX LPF CLK_EN                   
    [0:0]       0 (0x00)      TX DSM CLK_EN                   

bladeRF>

And I can't probe... so  maybe the switch works the oposite?  0=closed, 1=open?


regards


bglod
Posts: 45
Joined: Thu Jun 18, 2015 6:10 pm

Re: BB amplifier does not work and make reception not work.

Post by bglod » Mon Apr 17, 2017 8:54 am

Well, I suppose it wouldn't be the first time the documentation is incorrect. If Gqrx works and you can change the gains that way, then your boards should be fine.

If you take a look at Figure 3.1 in the Programming and Calibration Guide, it shows a block diagram of the RX path. Maybe you need to play with those other switches too (e.g. close BBBYP and disable RXVGA2)?

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