Hermes Homebrew Fault Finding

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Prem
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Re: Hermes Homebrew Fault Finding

Postby Prem » Fri Oct 13, 2017 6:09 am

Hi Scott,

I did further test on DAC signal with my scope.
At 1 MHz even with drive as low as 30 mW (FWD PWR S meter), I get the same non-Sine waveform from DAC out.

Then I monitored signal on DAC IC Pin 1 to Pin- 14. The pictures are as attached.
Only on pin-1 I get a square wave at 1 MHz.
On all other pins the waveform seen are different ! Also the frequency read was not 1 MHz !
On Pin-2 freq was above 3 MHz and other pins its was even higher values !!

What is the expected result ? All pins 1 to 14 to show same square wave at 1 MHz ??

Please advise further.

73s
Prem, A65BK
Attachments
DAC Pin-3 .JPG
DAC Pin-3 .JPG (93.03 KiB) Viewed 127 times
DAC Pin-2 .JPG
DAC Pin-2 .JPG (92.85 KiB) Viewed 127 times
DAC Pin-1 .JPG
DAC Pin-1 .JPG (89.08 KiB) Viewed 127 times
Last edited by Prem on Fri Oct 13, 2017 6:45 am, edited 1 time in total.
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Prem
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Re: Hermes Homebrew Fault Finding

Postby Prem » Fri Oct 13, 2017 6:11 am

Sending more Pin wave forms.

Rds,

Prem
Attachments
DAC Pin-6 .JPG
DAC Pin-6 .JPG (83.02 KiB) Viewed 126 times
DAC Pin-5 .JPG
DAC Pin-5 .JPG (91.78 KiB) Viewed 126 times
DAC Pin-4 .JPG
DAC Pin-4 .JPG (92.38 KiB) Viewed 126 times
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Re: Hermes Homebrew Fault Finding

Postby Prem » Fri Oct 13, 2017 6:46 am

Pin-12, 13 & 14 signals

Rds, Prem
Attachments
DAC Pin-14.JPG
DAC Pin-14.JPG (89.16 KiB) Viewed 125 times
DAC Pin-13.JPG
DAC Pin-13.JPG (89.41 KiB) Viewed 125 times
DAC Pin-12.JPG
DAC Pin-12.JPG (89.1 KiB) Viewed 125 times
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Re: Hermes Homebrew Fault Finding

Postby Prem » Fri Oct 13, 2017 7:04 am

Dear Scott,

Now I am bit confused, if my board is 14 bit or 16 bit version ?
How to read that ? My FPGA is 240 Pin EP3C40Q240C8N.
My U10 is LTC2208 CUP which has 16 DATA Pins !!
U5 DAC IC used is AD9744 ARU. it has 14 DATA Pins, Not 16 !!!

How to identify my board is 14 bit or 16 Bit !! ??

Also I tried to reload v3.2 Firmware rbf file using programmer software. Please see the pic arrached. After errasing previous V3.2, it completed programming upto 100%. But at last it showed error as seen in Pic " Make sure the correct interface is selected " !!

Later if I click the "Discover" button, it will show V3.2 !

Anything wrong here in my Firmware upload ?

But later I reloaded firmware V3.2 rbf file using bootloader program, placing J12. Now It completed without any error !

below link shows my video, how I uploaded firemware using bootloader.

https://www.youtube.com/watch?v=q3jaBNfI4Is

Finally the result from the scope display are same !!!

Please help me further.

Rds, Prem A65BK
Attachments
Firmware uploaded V3.2 rbf.JPG
Firmware uploaded V3.2 rbf.JPG (101.77 KiB) Viewed 122 times
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Re: Hermes Homebrew Fault Finding

Postby w-u-2-o » Fri Oct 13, 2017 11:49 am

Your board is a 16-bit Hermes. It is defined as such by the use of the 16-bit ADC, and the larger FPGA.

You video shows correct loading of the firmware using bootloader.

Your scope measurements are mostly not worth anything because the DAC runs at 125MHz and your 20MHz scope cannot keep up with that data rate on the data input lines.

At 1MHz, Pin 1 should be a 1MHz square wave. Pin 2 should be a 2MHz square wave. And so on.

Understand, Prem, that I am now "grasping at straws". This is an English expression that means to guess randomly at or pursue any apparent option, due to a lack of clear choices or information. Any further help I give may or may not be actual help! So if I lead you down some wrong path at this point, my apologies, but I have exhausted what I can definitively do on this problem. As long as you understand that, then....

Have you checked and rechecked connections at T1?

That you have a 1MHz square wave on Pin 1 now makes me suspicious of the REFIO signal on Pin 17, and how it is developed. At 1mW, 250mW and 500mW, what voltages do you measure on REFIO, Pin 17? Does your scope show that those voltages are stable? I don't know what those voltages should be, but it's worth looking at them.

The way drive is controlled in openHPSDR architecture radios is that the FPGA puts out a PWM waveform on a digital pin, which is low pass filtered to convert it to an analog voltage, which is then applied to the DAC REFIO pin. This allows the data word going into the DAC to always use all 14 bits, maintaining full dynamic range and waveform resolution in the digital domain, and the amplitude (drive) of the DAC output is controlled by the REFIO pin. Therefore: triple check all connections associated with that function on U3A (LMC6482AM), pins 1, 2 and 3, as well as all of the supporting passives. What do you see with your scope on Pin 3 of that IC?
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Re: Hermes Homebrew Fault Finding

Postby Prem » Fri Oct 13, 2017 3:18 pm

Hi Scott

What can be the minimum spec for a descent scope to buy which can cover all Hermes signal tracing ?
Which is the first point we expect a sine wave ? Is it at it at DAV ouput or T1 primary ?

Pine1 was at 1Mhz, 2 at 2 plus and so on itwas different.
Do you expect a faulty DAC IC ?

Rds. Prem
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Re: Hermes Homebrew Fault Finding

Postby w-u-2-o » Fri Oct 13, 2017 5:10 pm

I do not believe you will need a better oscilloscope to solve this problem. However, the highest frequency on the board is 125MHz.

The first place you will see a sine wave is at the DAC outputs.

Again, have you checked transformer T1 at the output of the DAC and its surrounding components?
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Re: Hermes Homebrew Fault Finding

Postby Prem » Fri Oct 13, 2017 5:41 pm

Hi Scott,

Connection around T1 sound good. Out from DAC is directly going to T1 primary and there 51Ohm resistor also connected .
Since DAC is generating Sine wave out and we find it is not happening !
In this case will T1 and rest of components will help us ?

Do you expect FPGA possible fault ? Else shall we try a replacement of DAC ?

Voltage at Pin 17 of DAC vary from 200 mV to 1.7 with drive change.
almost same voltage change at U3 Pin-3 also seen.

73s

Prem, A65BK.
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Re: Hermes Homebrew Fault Finding

Postby w-u-2-o » Fri Oct 13, 2017 7:52 pm

Prem,

I'm sorry, but at this point I don't know what to suggest next.

There are people who don't use the forum on both the Apache Yahoo Group, and the HPSDR mailing list. Perhaps if you post the photo of DAC output at 1MHz someone there may know exactly what is going wrong.

73,

Scott
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Re: Hermes Homebrew Fault Finding

Postby Prem » Sat Oct 14, 2017 2:15 am

Hi Scott,
It is quite unfortunate that none else is joining the forum discussions.
Finally at this stage I would request you again to help me to trace out why I get a FWD power S meter and RF power out even if I have not plugged a mic ? May be we can reach somewhere to a solution than going behind waveforms which we are struck in between.

Without Mic plugged and so no audio, how PSDR generate RF out iwhen MOX pressed. Since you know very well what is the process being happening inside, you can very much support me further to do some more trouble shooting.

Also I request other team members to flash some light into this discussion. Please share your thoughts even if not fully confident on the statement !
I double people are scared to put some statement or opinion against or different to ongoing discussions !!

Please support with your valuable advices.

" what can be the reason for me to get RF out even without my mic plugged in" This RF will vary with my drive as well as Mic gain. If I disable min, this RF power is not there !

Please note that this S meter reading is not a false reading. I get this RF power out in external meter. Also current consumption also in agreement with S meter reading. Means this is not a false reading at all , Threr is RF being output from final Ant jack!

Awaiting your valuable suggestions and advices.

73s

Prem, A65BK.
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Re: Hermes Homebrew Fault Finding

Postby w-u-2-o » Sat Oct 14, 2017 4:02 am

The normal noise level out of the CODEC with no microphone plugged in is -70dB. This is normally not enough to generate any substantive amount of RF output. However, since your DAC is generating an aberrant waveform, you see a substantial amount of RF when any amount of drive or noise is present, even a tiny bit.

73,

Scott
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Re: Hermes Homebrew Fault Finding

Postby Prem » Sat Oct 14, 2017 4:18 am

Hi Scott,

So shall I do focus my further checking to FPGA and DAC ? Until we get a Sine wave at DAC out, we need not further investigate further stages beyond T1. Is it ?
I have measured the signals at 20m and looks as if it is better than 1MHz. Please have a look into my below video post.

http://www.youtube.com/watch?v=CcRBmxd_yqg

Rds, Prem A65BK
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Re: Hermes Homebrew Fault Finding

Postby w-u-2-o » Sat Oct 14, 2017 11:42 am

As soon as you get a good sine wave from the DAC everything else will be perfect and there will be nothing else to investigate.

It does not look better at 20MHz, your scope is merely undersampling the waveform.
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Re: Hermes Homebrew Fault Finding

Postby Prem » Sat Oct 14, 2017 3:38 pm

Hi Friends,

Now I connected my Hermes plus my 10W drive amp and work FT8 mode using WSJTX. I could work few stations.
But still I could not resolve issue with SSB signal error. I work on 20m now.

73s

Prem, A65BK
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Re: Hermes Homebrew Fault Finding

Postby Prem » Wed Oct 18, 2017 4:09 am

Hi Phil,

Please have a look at the Two tone test screen shots with and without DUP on.

73s,

Prem, A65BK
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IMG_4793.JPG
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Re: Hermes Homebrew Fault Finding

Postby w-u-2-o » Wed Oct 18, 2017 11:11 am

Still looks broken. Exhausted my ability to figure out what that is, though. Still something to do with the FPGA/DAC.
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Re: Hermes Homebrew Fault Finding

Postby Prem » Wed Oct 18, 2017 2:10 pm

Hi

Can we conclude fault to foga or dac ?
Anything else to check ?

If nothing else can be the reason, we will try replace fpga. But how to remove it another nightmare for me

Rds

Prem
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Re: Hermes Homebrew Fault Finding

Postby Prem » Sat Oct 21, 2017 6:46 am

Hi Scott,

I have monitored the DAC IC Data in pins from 1 to 14 and slide show video captured as below.

I have viewed waveforms on all DAC IC data pins from 1 to 14 and result captures as a slide show video as below.

http://www.youtube.com/watch?v=zD-YrjdBSKA


Rds,
Prem, A65BK
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Re: Hermes Homebrew Fault Finding

Postby w-u-2-o » Sat Oct 21, 2017 11:26 am

Prem,

Good effort, and the idea of looking at the data on those pins to isolate the problem to the FGPA or DAC is a good one, however you don't have the right equipment to do it. First, your scope is too slow to resolve the 125MHz data rate, that is why the signals become unreadable after you get past pins 2 and 3. Second, even if you had a fast enough scope, what you really need is a 14 bit logic analyzer that can read the data and plot it out for you.

So, unfortunately, it is impossible to know if the data is correct from your video slide show.

73,

Scott
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Re: Hermes Homebrew Fault Finding

Postby Prem » Sat Oct 21, 2017 12:25 pm

Hi Scott,

What you expect ? the fault in FPGA or DAC ?

Rds, Prem
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Re: Hermes Homebrew Fault Finding

Postby w-u-2-o » Sat Oct 21, 2017 3:19 pm

Prem,

I'm sorry, I have no way to know.

73,

Scott

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