Probleme mit Abschwächer im Vorverstärker von DC2PD

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df5fh
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Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon df5fh » Sa Jan 27, 2018 4:28 pm

Hallo,

ich habe meinem Redpitaya den Vorverstärker von DC2PD gegönnt. Diesen habe ich zunächst ohne die I2C-Verbindung zum Redpitaya in Betrieb genommen und kann mit Powersdr sehen, dass der Vorverstärker funktioniert. Nun wollte ich auch den Abschwächer ausprobieren aber ich bekomme es nicht hin. Ich habe in Powersdr bei "Hardware Config" einen Haken bei Alex gemacht und bei "Options" den "Hermes Step Attenuator" enabled. Wenn ich nun auf der Oberfläche Werte mit dem S-ATT einstelle, würde ich erwarten, dass ich mit meinem Oszilloskop Clock und Daten auf dem I2C-Bus sehen kann. Da liegt aber ein konstanter 3V-Pegel an, keinerlei Bewegung. Im Redpitaya benutze ich das aktuellste Image von Pavel und habe den "SDR transceiver compatible with HPSDR" gestartet. Hat jemand Tipps für mich ?

Vy 73
Henning
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f6itu
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon f6itu » Sa Jan 27, 2018 10:59 pm

Hallo Henning

As far as I can judge, you probably have a hardware problem, not a software one.
- check if you have use the E2 connector, not the E1
- check if you didn't use a wrong pin of this E2 connector (Pin 9 for SCL, 10 for SDA
- first of all, disconnect the DC2PD from the E2 connector
- check SDA and SCL for any activity without any load. You should see a brief "strobe" when passing a frequency crossover point or changing the attenuator's value

if your I2C bus is alive without any connexion, switch off the preamp voltage. Check with a ohm-meter if you have a short between Vcc and SCA and /or SCL on the preamp side (mcp4725 input)

hope you will find the bug

73'
Marc f6itu
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df5fh
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon df5fh » So Jan 28, 2018 12:42 pm

Hello Marc,

thank you very much for your response. I checked your list but I have no success.

Here you can see the wire connection:

Bild

The I2C is connected with an oscilloscope:

Bild

When I click on S-ATT nothing happens here (both signals are at ca. 3V ):

Bild

The "Hermes Step Attenuator" is enabled:

Bild

Here you can see the S-ATT in postion 0dB. The rx-input is open, noise is at -130dB

Bild

When I increase the S-ATT, I would expect "traffic" on the I2C-Bus. But there is nothing. Surprisingly the noise is moving up. When I select an attenuator-value of 61dB the shown noise floor is at -70dB. What is the reason for this behavior ? (Ok, this is another question, this has nothing to do with my i2C-Problem)

Bild

Here the hardware config. The IP is correct, the Redpitaya on the first adress is powered off.

Bild

Marc, I checked if there is a short between Vcc and SCA and/or SCL ... it is not.

What can I check next ? Thank you for ideas ...

vy73
Henning
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f6itu
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon f6itu » So Jan 28, 2018 2:01 pm

Hi Henning

:-( just scratching my head.

There is a strong probability that your Red Pitaya's I2C IS working perfectly. The contrary would mean you have killed some gpio of your FPGA, and it would be a different and sad story

In fact, capturing the I2C signal with a tektro 2225 is possible, but you'll have to be lucky to spot it: you must set the trigger on clk (panel on the right side of the scope) and the "burst" is rather short and will pass the screen in a blink. I have the very same scope at home . As it is not a permament signal, your picture of the tektro screen is not really meaningful.

the permanent 3V "high" is absolutely normal, as I2C is an open collector output. And most of the time, pull-up resistors maintain the line in a "high" state.

Do you have a logic analyzer (or a friend who does ) ?
When I have problems with an I2C or SPI bus, I use a small gear like this one
https://www.ebay.com/itm/USB-Logic-Anal ... SwopRYgX55

it's a Saleae chinese clone you can use with a Sigrok interface (free and open source). You also can use the original Saleae software. It's the only efficient and safe way to test and "read" what is happening on a bus

If you cannot grab one of these small analyzer, you'll have to carefully look at your scope when trying to trigger your attenuator, and trim the scope timebase to "see" the activity of the bus. Pavel's software does the job almost independently of the client software

Just try to confirm the I2C activity. This step is important
73'
Marc
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Uli DF5SF
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon Uli DF5SF » So Jan 28, 2018 5:22 pm

Hi Henning,

I checked it with PowerSDR OpenHPSDR PS v3.3.9 (6/15/16) Mod.:12721/16. Very less experience with this software, normally I use piHPSDR .
You mentioned "When I increase the S-ATT, ....... Surprisingly the noise is moving up."
I have the same behaviour here. So I think the I2C is ok.

The SDA and SCL-Signal are very short. This is the signal If I change from 30 -> 31
LA1.png
73 de Uli, DF5SF
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df5fh
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon df5fh » So Jan 28, 2018 8:29 pm

Hello Uli, Marc

thank you for your I2C plot ... I would like it so much to repoduce this here in my shack :cry:

Possibly I was misunderstood at this point: The noisefloor is moving up and down with the current attenuator-value. Surprisingly is ... this happens without something connected to the rx input! There is no noise adding preamp connected ... Powersdr is doing this automatically for some reason. I can`t imagine why ? Uli, please, can you repoduce this ?

Today I have no idea what`s going wrong here. Marc, the hint with the cheap logic analyzer sounds very interessant. Just to have another option.
But I can`t imagine that an I2C signal with 40us clock time can be overlooked with an oszilloscope. If your mouse is on the ATT-field you can force more then one value by using the mouse-wheel (I estimate).

How can I isolate the problem ? Is it my Redpitaya or is it PowerSDR(-Configuraiotn) ? Can I test the I2C-Output with another Software ?

Vy 73
Henning
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pavel
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon pavel » Mo Jan 29, 2018 9:20 am

Hello Henning,

On one of your pictures, the I2C cable is connected to the scope but not to the preamp board. In this configuration, you won't see any I2C signals when changing the tuning frequencies. You'll only see some I2C signals when the SDR transceiver application starts on Red Pitaya.

The SDR transceiver application tries to detect the preamp board when it starts. It sends the I2C signals only if the preamp board is detected when the application starts.

So, to see the I2C signals, the preamp board has to be connected to Red Pitaya at the moment when the SDR transceiver application starts on Red Pitaya.

Best regards,

Pavel
Zuletzt geändert von pavel am Mo Jan 29, 2018 10:06 pm, insgesamt 1-mal geändert.
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Uli DF5SF
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon Uli DF5SF » Mo Jan 29, 2018 11:27 am

df5fh hat geschrieben:Hello Uli, Marc
Possibly I was misunderstood at this point: The noisefloor is moving up and down with the current attenuator-value. Surprisingly is ... this happens without something connected to the rx input! There is no noise adding preamp connected ... Powersdr is doing this automatically for some reason. I can`t imagine why ? Uli, please, can you repoduce this ?


Hello,

my meassurements without antenna. PowerSDR uncalibrated and Mode=CWU

S-ATT->Noisefloor->S-Meter(Signal)
0 -> -145 -> -110 dBm
10 -> -140 -> -106 dBm
20 -> -135 -> -100 dBm
30 -> -125 -> -90 dBm
40 -> -115 -> -81 dBm
50 -> -105 -> -70 dBm
60 -> -95 -> -60 dBm

The difference between noisefloor and S-meter is explained here: https://apache-labs.com/community/viewt ... f=6&t=2463
73 de Uli, DF5SF
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f6itu
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon f6itu » Mo Jan 29, 2018 12:45 pm

Pavel marks a point (and I feel stupid indeed)
you can't control a master/slave I2C dialog without connecting both

Marc
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Uli DF5SF
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon Uli DF5SF » Mo Jan 29, 2018 3:55 pm

Hello Henning,

I think there is a misunderstanding.
The Vorverstärker von DC2PD is no attenuator. It is an amplifier and with one jumper you can change the amplification range from
1.) -4.5dB to +43.5dB or to
2.) +7.5dB to +55.5dB
see also product info AD8331 here: http://www.analog.com/en/products/ampli ... d8331.html
73 de Uli, DF5SF
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df5fh
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon df5fh » Mo Jan 29, 2018 7:04 pm

Hello Pavel,

thank you very much, you fixed my problem!

I started your software on the Redpitaya and then I connected the preamp and was disappointed that is does not work. In the next step I disconnected the I2C-Bus from the preamp and connected it to the scope, to check, if there is a signal on the I2C. :D :D :D

Let me play with my new toy, I will report (or ask more) later. I`m excited ...

Thank you all for helping me !

Friendly regards
Henning
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DL5DLA
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon DL5DLA » Di Sep 18, 2018 8:46 am

Hello,
I have a similar problem with my DC2PD preamp and the red pitaya:

- Setup: In PowerSDR: HardwareConfig->Hermes:checked, HardwareOptions->Alex:cheched, Options->Hermes Step Att->Enable:checked.
- Preamp is connected when booting the redpitaya
- Constant voltage at pin 10, AD8331, no reaction when changing the Step Attenuator in PowerSDR. No visible impulses on the i2c lines.
- Noise floor on the PowerSDR goes up and down when changing the attenuator values but this even when no preamp is in between.

Different from Hennings observation above: when I reboot the redpitaya, I can clearly see some impulses on both i2c lines. I guess, it's not a hardware problem in my case. So either PowerSDR is not sending changes of the attenuator value to the red pitaya, or the red pitaya is not sending anything to the preamp in that phase.
May be that the red pitaya is probing the communication to the preamp, but is not satisfied with the answer of the preamp (address jumper J1 set to ground, address 0x60).

Currently I have no idea how to proceed searching for the error. Is it possible to check whether the software on the redpitaya has accepted the i2c signals from the preamp, or is there some kind of debugging mode?

Thanks for any help.

73
Peter
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pavel
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon pavel » Mi Sep 19, 2018 11:57 pm

Hello Peter,

is there some kind of debugging mode?


To check the I2C communication, you can try the i2c-write program from the sdr_transceiver_wspr project:

https://github.com/pavel-demin/red-pita ... 2c-write.c

It sends commands to DC2PD preamp. It can be run from the Red Pitaya command line with the following commands:

Code: Alles auswählen

cd apps/sdr_transceiver_wspr
./i2c-write 1234


Best regards,

Pavel
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DL5DLA
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Re: Probleme mit Abschwächer im Vorverstärker von DC2PD

Ungelesener Beitragvon DL5DLA » Fr Sep 21, 2018 9:36 am

Hi Pavel,
thanks for the help. I tried that and it works. I can see the impules now on the i2c lines. And - surprise - I do see them now also when using PowerSDR's step attenuator. No idea what was going wrong before. On my tests yesterday, I observed that in some cases I have to reboot the redpitaya to get it working, even if I didn't change the cabeling. May be the cable connections are somehow weak - I have to check that again.

Regards,
Peter

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