Re: Issue #4 Raspberry Pi 4 HDMI audio modules conflict with loopbacks
You can disable the HDMI audio in the config.text file in the boot folder. ?I am laid up and can not get to my computer to look up the specific line to add the ¡°,noaudio¡± to the end of the dev= line and do not remember the driver that the video is using.?
If you post the contents of config.txt I can tell you the link to modify. ? A search for noaudio in the group may also work
73
Evan
AC9TU
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Are you sure you can do I2S through some GPIO pins? Otherwise it would not work as Pi replacement for the sBitx.
- Rafael
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On 2/4/24 06:57, Ken N2VIP wrote: Steve,
The $279 computer was the one you linked to that had GPIO pins, from Tom's Hardware website:
/
And, BTW, you can get Arduino and/or Pi-compatible GPIOs on an Intel platform if that's what you want:
It's a bit pricier now, but overall it seems quite possible that an Intel variant could take away a lot of Pi's lunch money sooner or later. /
That board is the $279 one I was talking about, a bare board (no Case! Fan! Power!) with a Celeron J4105 and some AMD processor (not N110) and 8 gigs of RAM, which compares very nicely with an 8 Gig RPi 5 board at $80.
In other words comparing "apples to apples", essentially, if not precisely.
Ken, N2VIP
On Feb 3, 2024, at 23:02, Steve Barkes <sbarkes@...> wrote:
250% is not quite accurate.? My N100 came with 16GB ram, 256GB of SSD storage, built in power supply and a case.? You need to add a case, a fan, a power supply, an sdcard or other storage etc to the RPi to make a fair comparison.? Not trying to ruffle any feathers but we should compare apples to apples.
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Re: Radio S32LE samples don't go negative?
Hi Dave, On 2/3/24 23:29, Dave, N1AI wrote: On Sat, Feb 3, 2024 at 05:35 PM, Rafael Diniz wrote:
I'm playing with csdr [1] and it is pretty cool.
[1]
*Aside #1:* I found it difficult to get that version of csdr to build on newer systems.
Also as it says when you load the page, that version hasn't been maintained since 2020
I found the best version to use these days.
*It comes from* *the openwebrx project which is a heavy user of csdr.*
There are some old CFLAGS. I made a fork and fixed the Makefile to have sane intel and arm parameters: They also publish Python wrappers,
According to a video I watched, pycsdr makes it pretty easy to put together DSP piplelines.
Probably more efficient than using bash, because unix/linux pipes are inefficient.
I haven't tried coding to pysdr yet, though.
*Aside #2:* I now have a Hermes Lite 2 feeding 8 streams of data to a dedicated Pi5 doing FT8 decoding.
That Pi5 is running openwebrx headless, it's pretty easy to manage.
If you look for spots from n1ai on pskreporter.info you will see what I'm harvesting.
Openwebrx would run well in the sBitx, I'll install here to play with.
Just to be sure - it makes no sense to add this DC component to tx
/ speaker paths, right?
[1]
Personally I would say it doesn't make sense.
I can't explain why it is happening.
Someone who is better with schematics and data sheets than I am should look into it, IMO.
That is my feeling too. Cheers, Rafael
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Re: Issue #4 Raspberry Pi 4 HDMI audio modules conflict with loopbacks
Paul,
Your perseverance on this topic is very sympathetic and I hope you can fulfill your original idea.
This is how you can get from "PlughW: 1.0" and "Plughw: 2.1" to [Sbitxdigiout] and [Sbitxdigiin].
The latter are more understandable to users.
This is where teamwork can be seen, where everyone adds their own knowledge to achieve a common goal.
--
Gyula HA3HZ
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Re: Issue #4 Raspberry Pi 4 HDMI audio modules conflict with loopbacks
Actually had a bit of a google after I wrote the reply, this may be more help:? snd-aloop is a module so the key is to change the id associated with it to? make it more identifiable, will still need a line for each loopback along the lines of : Ok I did a test, I want to know the answer to this too, NOTE - I haven't run the sbitx app yet with these changes, it might not work from that point of view but answers the device naming question I think. I tried two changes:
- ?sudo nano /etc/modprobe.d/alsa-base.conf
-
options (efault) index=-2
options snd-aloop index=1 id=sbitx-digi-out
options snd_usb_audio index=5
This resulted in no change to the output from?cat /proc/asound/modules
pi@sbitx:~ $ cat /proc/asound/modules
?0 (efault)
?1 snd_aloop
?2 snd_aloop
?3 snd_aloop
?4 snd_aloop
?5 snd_usb_audio
pi@sbitx:~ $ the output from p i@sbitx:~ $ cat /proc/asound/cards ?0 [audioinjectorpi]: audioinjector-p - audioinjector-pi-soundcard ? ? ? ? ? ? ? ? ? ? ? audioinjector-pi-soundcard ?1 [sbitxdigiout? ?]: Loopback - Loopback ? ? ? ? ? ? ? ? ? ? ? Loopback 1
?
I trimmed the rest as there was no change. The next test was updating /etc/rc.local as I suggested as a possible option earlier: pi@sbitx:~ $ sudo nano /etc/rc.local
? GNU nano 7.2? ? ? ? ? ? ? ? ? ? ? /etc/rc.local? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
modprobe snd-aloop enable=1,1,1,1 index=1,2,3,4 id=sbitxdigiout,sbitxdigiin,sbitxusbout,sbitxusbin
This after a reboot produces:
pi@sbitx:~ $ cat /proc/asound/cards
?0 [audioinjectorpi]: audioinjector-p - audioinjector-pi-soundcard
? ? ? ? ? ? ? ? ? ? ? audioinjector-pi-soundcard
?1 [sbitxdigiout? ?]: Loopback - Loopback
? ? ? ? ? ? ? ? ? ? ? Loopback 1
?2 [sbitxdigiin? ? ]: Loopback - Loopback
? ? ? ? ? ? ? ? ? ? ? Loopback 2
?3 [sbitxusbout? ? ]: Loopback - Loopback
? ? ? ? ? ? ? ? ? ? ? Loopback 3
?4 [sbitxusbin? ? ?]: Loopback - Loopback
? ? ? ? ? ? ? ? ? ? ? Loopback 4
?5 [II? ? ? ? ? ? ?]: USB-Audio - Jabra EVOLVE 30 II
? ? ? ? ? ? ? ? ? ? ? GN Audio A/S Jabra EVOLVE 30 II at usb-0000:01:00.0-1.4, full speed
pi@sbitx:~ $ no change to the output from?
pi@sbitx:~ $ cat /proc/asound/modules
?0 (efault)
?1 snd_aloop
?2 snd_aloop
?3 snd_aloop
?4 snd_aloop
?5 snd_usb_audio
pi@sbitx:~ $ as before. Just needs to test sbitx app now to see if it still runs with these changes :-) Sbitx app started, I got sound, no antenna connected as I in the lounge working all this out while watching tv with the boss :-) Built in FT8 appears to work into a dummy load anyway. My JTDX needs work when I have a full size monitor available but this screenshot from settings shows the new device names are available now for digital software configuration:  initial signs look positive Regards Paul G0KAO ?
?
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Re: Issue #4 Raspberry Pi 4 HDMI audio modules conflict with loopbacks
Hi Dave If you are able to identify the HDMI interface and set its priority as I did for the USB ports then at least you can prevent clashes with the loopback interfaces. The one bit I probably haven¡¯t quite answered is the naming of the loopback interfaces, though I think looking at the alsa modules config might be the starting point.? This bit of config would be the same regardless of the codebase as it is core sound config from a naming perspective, though that would have an impact on the code as references to the loopbacks would then have to be updated to reflect the new device names. I am now at the point where I need to understand the code architecture at a higher level to see how the code modules (assuming its modular) interact with each other.? While Ashar pointed me at the mixer section of the sbitx.sound.c code, it is called by something else that passes the device names, hence me needing to understand the code at an architectural/flow level before digging in. Maybe in doing so we can get to device naming at the same time.? From what I can tell in the code Ashar refers to the aplay -l (or -L) command to get device names, what I don¡¯t see is how this is done and its not in the sbitx.sound.c code. ALSA config will be the source of naming of devices but on reflection maybe the loopbacks could be individually named in the /etc/rc.local file instead of using the combined name of snd-aloop for all devices, try creating a line for each loopback e.g.
modprobe sbitx-digi-out enable=1 index=1 modprobe sbitx-digi-in enable=1 index=2
Instead of
modprobe snd-aloop enable=1,1,1,1 index=1,2,3,4
I suspect this is where /proc/asound/modules gets the loopback names from, do cat /proc/asound/modules to see what I mean.
I recall some references to snd-aloop in the code so it may need tweaking to reflect these changes.
Hope this helps in some way
Regards Paul G0KAO
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Steve,
The $279 computer was the one you linked to that had GPIO pins, from Tom's Hardware website:
And, BTW, you can get Arduino and/or Pi-compatible GPIOs on an Intel platform if that's what you want:?
?
It's a bit pricier now, but overall it seems quite possible that an Intel variant could take away a lot of Pi's lunch money sooner or later.
That board is the $279 one I was talking about, a bare board (no Case! Fan! Power!) with a Celeron J4105 and some AMD processor (not N110) and 8 gigs of RAM, which compares very nicely with an 8 Gig RPi 5 board at $80.
In other words comparing "apples to apples", essentially, if not precisely. Ken, N2VIP On Feb 3, 2024, at 23:02, Steve Barkes <sbarkes@...> wrote:
250% is not quite accurate.? My N100 came with 16GB ram, 256GB of SSD storage, built in power supply and a case.? You need to add a case, a fan, a power supply, an sdcard or other storage etc to the RPi to make a fair comparison.? Not trying to ruffle any feathers but we should compare apples to apples.
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250% is not quite accurate.? My N100 came with 16GB ram, 256GB of SSD storage, built in power supply and a case.? You need to add a case, a fan, a power supply, an sdcard or other storage etc to the RPi to make a fair comparison.? Not trying to ruffle any feathers but we should compare apples to apples. ? I own many RPi (at least 10 [3¡¯s and 4¡¯s and two 400¡¯s but no RPi5 yet) and use for my webserver, a couple of development machines, a weather station, a D-Star hotspot, gaming and other things.? I also own two different N100 type computers, a Mele Quieter 3 to control my telescope, mount, cameras, focusers, filter wheels and astronomy related equipment to do astrophotography, spectroscopy and photometry, and a Kamrui dedicated as a NAS server running OpenMediaVault. ? The RPi would never work for Astronomy as there isn¡¯t the software to support all I need to do.? It¡¯s all Windows based. ? The N100 won¡¯t work for the SBITX as I don¡¯t have any digital and analog ports? to control the radio.? No hardware interface to control the radio bits and bobs. ? Horses for courses.? Decide what you want to do and pick the platform that best supports it.? And it¡¯s OK to own more than one! ? Steve W5RRX ?
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From: [email protected] < [email protected]> On Behalf Of Ken N2VIP Sent: Saturday, February 3, 2024 6:37 PM To: [email protected]Subject: Re: [BITX20] sBIT USB boot ? Dave, I'm sorry I appear to have upset you - in the context of this mail list, I asserted that it would require a significant effort to use a $100ish N100 system in a uBitx, and you agree with me, as best I understand your responses. I never advocated the RPi was a better desktop device than the N100 boards we are generally discussing - I've been discussing embedded applications, like the *current* uBitx design. As for the cost differential, I pushed back on the characterization of the linked-to board as "a bit pricier now" - it's 250% more expensive than the bare RPi 5 board with 8 gigs of RAM, that's not just "a bit pricier" in my opinion, but opinions vary. And I will concede, adding items to an RPi to make it a convenient desktop system does raise the cost beyond the cost of the board alone - obviously - but I am not advocating to use the RPi as a desktop, on the other hand you *are* advocating to use an N100 in an embedded application like the uBitx. If you really feel the need to respond, please, let's take this off-list - I doubt many here are interested in any further discussion on this matter. Ken, N2VIP
On Feb 3, 2024, at 17:09, Dave, N1AI <n1ai@...> wrote:
I guess you just aren't following along, because I just wrote "It's a bit pricier now, but overall it seems quite possible that an Intel variant could take away a lot of Pi's lunch money sooner or later", and earlier in this thread (?here ) I wrote "Jeff is right that the Pi world requires you to select, purchase and assemble more 'stuff' to get a useful setup whereas most SFF PCs come with all the stuff you need right out of the box" and provided links to Jeff's video which shows if you price out all the stuff you need to buy to use a Pi 5 in a desktop configuration then you spend a lot more than the $85 or so that a raw Pi 5 8GB costs.? Want power?? More money!? Want a fan?? More money!? Want a case?? More money!? Want storage faster than a micro sd card?? More money!
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Dave, I'm sorry I appear to have upset you - in the context of this mail list, I asserted that it would require a significant effort to use a $100ish N100 system in a uBitx, and you agree with me, as best I understand your responses.
I never advocated the RPi was a better desktop device than the N100 boards we are generally discussing - I've been discussing embedded applications, like the *current* uBitx design.
As for the cost differential, I pushed back on the characterization of the linked-to board as "a bit pricier now" - it's 250% more expensive than the bare RPi 5 board with 8 gigs of RAM, that's not just "a bit pricier" in my opinion, but opinions vary.
And I will concede, adding items to an RPi to make it a convenient desktop system does raise the cost beyond the cost of the board alone - obviously - but I am not advocating to use the RPi as a desktop, on the other hand you *are* advocating to use an N100 in an embedded application like the uBitx.
If you really feel the need to respond, please, let's take this off-list - I doubt many here are interested in any further discussion on this matter.
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On Feb 3, 2024, at 17:09, Dave, N1AI <n1ai@...> wrote:
I guess you just aren't following along, because I just wrote " It's a bit pricier now, but overall it seems quite possible that an Intel variant could take away a lot of Pi's lunch money sooner or later", and earlier in this thread (? here ) I wrote "Jeff is right that the Pi world requires you to select, purchase and assemble more 'stuff' to get a useful setup whereas most SFF PCs come with all the stuff you need right out of the box" and provided links to Jeff's video which shows if you price out all the stuff you need to buy to use a Pi 5 in a desktop configuration then you spend a lot more than the $85 or so that a raw Pi 5 8GB costs.? Want power?? More money!? Want a fan?? More money!? Want a case?? More money!? Want storage faster than a micro sd card?? More money!
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Issue #4 Raspberry Pi 4 HDMI audio modules conflict with loopbacks
Referring to:?
Since my other comments on other issues have gone unanswered, I will try to discuss this here.
A screenshot of part of the issue:
I've talked about this a few times in this group:
/g/BITX20/message/108542? -- you don't have to rely on order of discovery if you use proper names
/g/BITX20/message/108485? -- stop using numbers, start using names
A fix is IMO pretty easy:
Create and use a new git branch so sending a PR is easier ('git checkout -b sbitx-alsa-names' will do this)
Go into sbitx.c and change?"plughw:0,0" to?"plughw:CARD=audioinjectorpi,DEV=0".
Go into sbitx_sound.c and change?"plughw:1,0" to?"plughw:CARD=Loopback,DEV=0".
Go into sbitx_sound.c and change?"plughw:2,1" to?"plughw:CARD=Loopback_1,DEV=1".
Rebuild the code and test that the sbitx app still works for rx and tx of voice modes.
Then test that the sbitx app still works with fldigi and/or wsjt-x external digital apps.
Then change /boot/config.txt to not disable HDMI audio (or standard broadcom headphone jack either).
Reboot and do the same tests.
Then plug in a USB headset or soundcard dongle, reboot, retest.
I'm pretty sure it will all just work based on the testing I did earlier.
It it works, send a PR to the ?repo and hopefully some day the fix will get merged.
I would do this, but my code base is now so different than the afarhan repo that it doesn't make sense for me to be the one to do it.
--
Regards,
Dave, N1AI
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Re: Radio S32LE samples don't go negative?
On Sat, Feb 3, 2024 at 05:35 PM, Rafael Diniz wrote:
I'm playing with csdr [1] and it is pretty cool.
[1]?
Aside #1: I found it difficult to get that version of csdr to build on newer systems.
Also as it says when you load the page, that version hasn't been maintained since 2020
I found??is the best version to use these days.
It comes from the openwebrx project which is a heavy user of csdr.
They also publish Python wrappers,??
According to a video I watched, pycsdr makes it pretty easy to put together DSP piplelines.
Probably more efficient than using bash, because unix/linux pipes are inefficient.
I haven't tried coding to pysdr yet, though.
Aside #2: I now have a Hermes Lite 2 feeding 8 streams of data to a dedicated Pi5 doing FT8 decoding.
That Pi5 is running openwebrx headless, it's pretty easy to manage.
If you look for spots from n1ai on pskreporter.info you will see what I'm harvesting.
Just to be sure - it makes no sense to add this DC component to tx / speaker paths, right?
[1]
Personally I would say it doesn't make sense. I can't explain why it is happening. Someone who is better with schematics and data sheets than I am should look into it, IMO. ? -- Regards, Dave, N1AI
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On Sat, Feb 3, 2024 at 04:46 PM, Ken N2VIP wrote:
On Feb 3, 2024, at 14:43, Dave, N1AI <n1ai@...> wrote:
The point I was trying to make is that Upton's tiny desktop concept risks getting buried by N100 or similar systems.
My point was they were designed for different use cases.
You wrote "his goal was a $100ish desktop?that required a TV for output that could be used in education for third-world students using phone chargers, cheap keyboards/mice, etc." -- how is that use case different from what you can do with a $100-ish N100???
Then consider the N100 can run far more software natively and is more expandable so quite possibly a better purchase than a Pi 5 desktop.
?
Overall IMO this, and the newly-announced IPO, will put pressure on Upton and team to crank up the innovation.
RPi Foundation has been building selling *huge* numbers of boards for embedded applications to industrial customers. I haven't heard about an IPO, but I suspect it will allow RPi Foundation to focus on educational issues and applications and the spin-off commercial organization can focus on industrial issues and applications, as well as (I imagine) help sponsor RPi Foundation.
N.B. Your linked-to alternative is priced at $279, more than 3x the cost of an 8 Gig RPi 5...
I guess you just aren't following along, because I just wrote "It's a bit pricier now, but overall it seems quite possible that an Intel variant could take away a lot of Pi's lunch money sooner or later", and earlier in this thread (?here ) I wrote "Jeff is right that the Pi world requires you to select, purchase and assemble more 'stuff' to get a useful setup whereas most SFF PCs come with all the stuff you need right out of the box" and provided links to Jeff's video which shows if you price out all the stuff you need to buy to use a Pi 5 in a desktop configuration then you spend a lot more than the $85 or so that a raw Pi 5 8GB costs.? Want power?? More money!? Want a fan?? More money!? Want a case?? More money!? Want storage faster than a micro sd card?? More money!
I get it, Pi excels at embedded applications, but hfsignals.com sells board-only setups and ones in cases, and most of the board-only units seem to stay in people's shacks, from what I read on this forum.? I own one of each and my board-only unit is probably never going into a case.? I might have considered interfacing it to something other than a Pi, but the mechanical design pretty much rules that out in the near term.
? -- Regards, Dave, N1AI
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Re: Radio S32LE samples don't go negative?
Thanks for all the answers. Does it makes sense to use a dc blocking filter to mic and radio rx paths? I'm playing with csdr [1] and it is pretty cool. Just to be sure - it makes no sense to add this DC component to tx / speaker paths, right?
[1]
- Rafael
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On 2/3/24 20:32, Gordon Gibby wrote: I¡¯m sure you know this but a spike in the frequency domain at 0 Hz is a DC constant offset in the time domain.
On Feb 3, 2024, at 15:21, Dave, N1AI <n1ai@...> wrote:
?On Sat, Feb 3, 2024 at 10:45 AM, Raj vu2zap wrote:
See the display difference on your scope in AC and DC mode.
You seem to be confirming Gordon's suggestion that could be a constant positive DC offset to the signal delivered to the Wolfson Codec's ADC which gets reflected in the digital values produced by the Wolfson Codec ADC.
This is different from Farhan's "DC Spike" which is indeed a spike and not a constant, and is in the frequency domain, and is centered around zero Hertz.
--
Regards,
Dave, N1AI
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Re: Radio S32LE samples don't go negative?
Hi Farhan,
I'm discussing about the samples I'm reading and writing from/to the wm8731 through ALSA API, not to do with high level software processing.
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On 2/3/24 14:09, Ashhar Farhan wrote: We zero out all bins except the central bins as a part of convolution filtering.
On Sat, Feb 3, 2024, 6:35 PM Rafael Diniz <rafael@...> wrote:
And for transmit / speaker, should such offset be used or 0 centered
sample signal can be used?
- Rafael
On 2/3/24 12:56, Ashhar Farhan wrote:
> This offset will show as dc spike (and it does) on bin zero. We
don't
> display or use that bin at all.
> - f
>
> On Sat, Feb 3, 2024, 5:01 PM Rafael Diniz
<rafael@...> wrote:
>
>? ? ?There seem to be an offset according to capture level and signal
>? ? ?intensity, but I can not (at least not easily) determine the
offset.
>
>? ? ?- Rafael
>
>? ? ?On 2/3/24 09:37, Gordon Gibby wrote:
>? ? ?> Is there a constant offset?? ?Try listening to a steady
carrier
>? ? ?which should result in a sine wave in the audio.
>? ? ?>> On Feb 3, 2024, at 04:21, Rafael Diniz
<rafael@...>
>? ? ?wrote:
>? ? ?>>
>? ? ?>> ?There is something wrong. I'm looking at the samples I get
>? ? ?from the radio rx path - I don't see negative samples, just
>? ? ?positive ones, but the sample format is signed 32 bits. When
>? ? ?reading from loopback, for example, I get the negative and
>? ? ?positive samples, as expected. This explains weird behaviors
I was
>? ? ?experiencing. Anyone can confirm this issue?
>? ? ?>>
>? ? ?>> Cheers,
>? ? ?>> Rafael
>? ? ?>>
>? ? ?>>
>? ? ?>>
>? ? ?>>
>? ? ?>>
>? ? ?>>
>? ? ?>>
>? ? ?>
>? ? ?>
>? ? ?>
>? ? ?>
>
>
>
>
>
>
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On Feb 3, 2024, at 14:43, Dave, N1AI <n1ai@...> wrote:
The point I was trying to make is that Upton's tiny desktop concept risks getting buried by N100 or similar systems. My point was they were designed for different use cases. <snip> Overall IMO this, and the newly-announced IPO, will put pressure on Upton and team to crank up the innovation. RPi Foundation has been building selling *huge* numbers of boards for embedded applications to industrial customers. I haven't heard about an IPO, but I suspect it will allow RPi Foundation to focus on educational issues and applications and the spin-off commercial organization can focus on industrial issues and applications, as well as (I imagine) help sponsor RPi Foundation. N.B. Your linked-to alternative is priced at $279, more than 3x the cost of an 8 Gig RPi 5... Take care, Ken, N2VIP
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Re: Radio S32LE samples don't go negative?
On Sat, Feb 3, 2024 at 03:32 PM, Gordon Gibby wrote:
I¡¯m sure you know this but a spike in the frequency domain at 0 Hz is a DC constant offset in the time domain. ?
I do, and should have pointed that out, so I thank you for your clarification. ? -- Regards, Dave, N1AI
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On Sat, Feb 3, 2024 at 09:27 AM, Ken N2VIP wrote:
The N100 vs RPi 5 debate seems to ignore those 40 pins on the RPi that the N100 solutions lack.
Are we trying to solve a software problem or a hardware problem?
I think you'd be hard-pressed to just "drop in" an N100 system in a device like the uBitx, there would be a significant effort to interface the N100 system to a uBitx board I imagine.
True.
N100 systems are great values and solve a number of problems, but they are not suitable in some applications the RPi excels at, namely embedded applications.
If your application doesn't require the 40 pin GPIO header, why are you using an RPi?
NOTE: if $100-150 N100 systems were available at the time, Mr Upton would never have developed the RPi - his goal was a $100ish desktop that required a TV for output that could be used in education for third-world students using phone chargers, cheap keyboards/mice, etc.
Exactly. The point I was trying to make wasn't that you can drop a N100 into a sbitx/ubitx and rock and roll. The point I was trying to make is that Upton's tiny desktop concept risks getting buried by N100 or similar systems. There really is little price difference between Pi 5 and N100, and (IMO) benchmarks show the N100 is a bit faster and definitely more expandable. Overall IMO this, and the newly-announced IPO, will put pressure on Upton and team to crank up the innovation. Hopefully the sbitx community is prepared for things to keep moving rapidly. And, BTW, you can get Arduino and/or Pi-compatible GPIOs on an Intel platform if that's what you want:? ? It's a bit pricier now, but overall it seems quite possible that an Intel variant could take away a lot of Pi's lunch money sooner or later. ? -- Regards, Dave, N1AI
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Re: Radio S32LE samples don't go negative?
I¡¯m sure you know this but a spike in the frequency domain at 0 Hz is a DC constant offset in the time domain. ?
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Show quoted text
On Feb 3, 2024, at 15:21, Dave, N1AI <n1ai@...> wrote:
?On Sat, Feb 3, 2024 at 10:45 AM, Raj vu2zap wrote:
See the display difference on your scope in AC and DC mode.
You seem to be confirming Gordon's suggestion that could be a constant positive DC offset to the signal delivered to the Wolfson Codec's ADC which gets reflected in the digital values produced by the Wolfson Codec ADC. This is different from Farhan's "DC Spike" which is indeed a spike and not a constant, and is in the frequency domain, and is centered around zero Hertz. ? -- Regards, Dave, N1AI
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Re: Radio S32LE samples don't go negative?
On Sat, Feb 3, 2024 at 10:45 AM, Raj vu2zap wrote:
See the display difference on your scope in AC and DC mode.
You seem to be confirming Gordon's suggestion that could be a constant positive DC offset to the signal delivered to the Wolfson Codec's ADC which gets reflected in the digital values produced by the Wolfson Codec ADC. This is different from Farhan's "DC Spike" which is indeed a spike and not a constant, and is in the frequency domain, and is centered around zero Hertz. ? -- Regards, Dave, N1AI
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Update.
I fitted a Pi3 and it¡¯s booting but whilst I get noise. There is no RX of signals. Maybe I fried something else?
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HA3HZ
Dave, N1AI
Dave, N1AI