Mirror example "ringing" at sharp transistions

[matpalm]

first off : running old R3 / 10.24 board if that's anything to do with it...

$ openFPGALoader --scan-usb
found 14 USB device
Bus device vid:pid       probe type      manufacturer serial               product
003 023    0x1209:0xc0ca dirtyJtag       apf.audio    2D18312B19181D4A     Tiliqua R3 apfbug-beta4-1-g9b45

when running the mirror example ( at current HEAD 3f2f297 )

pdm dsp build --dsp-core=mirror --hw r3
pdm flash archive build/dsp-mirror-r3/dsp-mirror*.tar.gz --slot 0 --noconfirm

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i get a smooth result for sine wave ( at about 200Hz )

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but get a ringing for a saw wave at one of the sharp transitions

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same for a square wave...

these images are from a joranalogue generate 3 but see the same witrh a intellijel dixie 2

[matpalm]

oh wait... i'm on apfbug-beta4 ..
i should update to beta5 i guess... https://github.com/apfaudio/apfbug/releases

[matpalm]

hmmm. can't seem to update the rasp pi?

hold down the BOOTSEL and it mounts ok...

$ ls /media/mat/RPI-RP2
INDEX.HTM  INFO_UF2.TXT

$ sudo demsg
[22040.100981] usb 3-3: new full-speed USB device number 38 using xhci_hcd
[22040.250032] usb 3-3: New USB device found, idVendor=2e8a, idProduct=0003, bcdDevice= 1.00
[22040.250041] usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[22040.250045] usb 3-3: Product: RP2 Boot
[22040.250049] usb 3-3: Manufacturer: Raspberry Pi
[22040.250052] usb 3-3: SerialNumber: E0C9125B0D9B
[22040.252078] usb-storage 3-3:1.0: USB Mass Storage device detected
[22040.252266] scsi host6: usb-storage 3-3:1.0
[22041.311552] scsi 6:0:0:0: Direct-Access     RPI      RP2              3    PQ: 0 ANSI: 2
[22041.311947] sd 6:0:0:0: Attached scsi generic sg2 type 0
[22041.313067] sd 6:0:0:0: [sdc] 262144 512-byte logical blocks: (134 MB/128 MiB)
[22041.313958] sd 6:0:0:0: [sdc] Write Protect is off
[22041.313964] sd 6:0:0:0: [sdc] Mode Sense: 03 00 00 00
[22041.315950] sd 6:0:0:0: [sdc] No Caching mode page found
[22041.315954] sd 6:0:0:0: [sdc] Assuming drive cache: write through
[22041.323708]  sdc: sdc1
[22041.323926] sd 6:0:0:0: [sdc] Attached SCSI removable disk

but when i try to copy the updated r3 file...

cd /tmp/
wget https://github.com/apfaudio/apfbug/releases/download/apfbug-beta5/apfbug-r3.uf2
cp apfbug-r3.uf2 /media/mat/RPI-RP2

the copy command returns without error but the the pi has been unmounted ..
( looks like the write failed and it rebooted? )

$ sudo dmesg
[22063.557807] usb 3-3: USB disconnect, device number 38
[22063.567983] FAT-fs (sdc1): unable to read boot sector to mark fs as dirty
[22064.114552] usb 3-3: new full-speed USB device number 39 using xhci_hcd
[22064.267618] usb 3-3: New USB device found, idVendor=1209, idProduct=c0ca, bcdDevice= 1.11
[22064.267626] usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[22064.267630] usb 3-3: Product: Tiliqua R3 apfbug-beta4-1-g9b45
[22064.267633] usb 3-3: Manufacturer: apf.audio
[22064.267636] usb 3-3: SerialNumber: 2D18312B19181D4A
[22064.300729] cdc_acm 3-3:1.1: ttyACM0: USB ACM device
[22074.147261] usb 3-3: USB disconnect, device number 39

[vk2seb]

Interesting finding, I wonder if it's on the ADC or DAC side. I did do a frequency sweep on the frontends during bring up and didn't see a resonance but obviously there's something there. At the moment all the codec's built-in filters are switched off, I suspect fiddling with the codec registers might help this. Worst case I can limit the slew rate with a gateware change. There's also the option to compile mirror with --fs-192khz which might make a difference (default is 48khz).

I'm travelling at the moment without a scope but perhaps I'll give it an investigation in 1wk after I'm back

For the bootloader I think the rp2040 usually needs a sync after the cp for it to pick up the write. The rp2040 bootloader is burned into the silicon ROM, there's no custom code there. Anyway I think beta4 should be fine for you, beta5 just contained some stuff for rev5. As long as you can flash the device with openFPGALoader or pdm flash archive there's no need to touch the rp2040, its only function is a JTAG adapter and USB/serial converter

[vk2seb]

I would likely start by playing with these

[matpalm]

--fs-192khz and it all disappears!
nothing to see here :D
happy to close ( unless there's something you want to dig into... )

[matpalm]

( can see it creep back in when i get into the kHz range so might still be worth a sanity check )

[vk2seb]

Cool good to hear it's improved but yeah let's leave this one open if the ringing is still there, happy to look at it once I'm back from travelling this week.