[SOLVED] XT control pots make sounds gritty

Hello everyone,

I finished the assembly of a TubeOhm XT control board. I uploaded a firmware using latest git and a usbtiny.

What’s working:

  • it boots normally
  • the ‘init’ patch sounds normal
  • all pots and buttons modify the right parameter (I can see the corresponding update on the screen, and the sound changes accordingly)
  • changing a value with the encoder works perfectly

What’s not working:

  • changing a value with a pot also makes the sound become ‘gritty’: it ressembles the original one, but sounds as it is ‘crushed’. And this happens whatever the pot. This does not happen with a button-triggered change (e.g. changing the shape of an osc).

The filter board I use is a TubeOhm Ladder, that I tested using the control board of another shruthi. Though the filter board might have some problems (I cannot really tune the resonance, but this is a (unrelated I think) problem), it sounds normal. I tried to see if another parameter changes along the one I control with a pot, but I could not spot one.

Does it ring a bell to someone?

Cheers,

Stephane

PS:

  • I use a smaller EEPROM (128kbits)
  • the control board and the filter are connected with a set of 8 wires plugged into the 8 pin header, with the header loosely plugged (ie not soldered) in the control board, and bended so that the holes touch the pins. Note that I used this setup with the functioning regular control board with no problem. And right after the boot, the sound is normal.
  • most of the components come from tayda, including the ICs (especially the CD4051’s)

> using latest git

You mean you compiled the code yourself? With which compiler?

yes:

$ /usr/local/CrossPack-AVR/bin/avr-g++ --version
avr-g++ (GCC) 4.3.3
Copyright © 2008 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

btw, I have multiple errors when uploading, but since it eventually succeeds, I thought it would be ok:

avrdude: reading input file "shruthi/data/factory_data/internal_eeprom_xt.hex"
avrdude: writing eeprom (2048 bytes):

Writing | ############################################### | 93% 7.45s
avrdude: error: usbtiny_send: usb_control_msg(DeviceRequestTO): transaction timed out (expected 128, got -60)

avrdude: error: usbtiny_receive: usb_control_msg(DeviceRequestTO): unknown error (expected 4, got -1)

avrdude: error: usbtiny_receive: usb_control_msg(DeviceRequestTO): unknown error (expected 4, got -1)

[…]

avrdude: error: usbtiny_receive: usb_control_msg(DeviceRequestTO): unknown error (expected 4, got -1)
avrdude: 448 retries during SPI command
Writing | ################################################## | 100% 11.18s

What is the size of the hex file?

and I just tried with the firmware available on the mutable site, same problem…

here is an example: first right after init, then I tweak resonance…

moose says: 63730

I thought it would be a CPU overflow glitch, but it doesn’t seem to be the case.

Does the screen refresh rapidly? Do you see a “!” in the corner sometimes?

did you stuff all the jumpers for the volume?

@altitude: good spot, that was it, I forgot the jumper for analog volume control, my bad…

pichenettes,altitude: thank your for your support, even if I feel dumb each time I make an error like this, I always appreciate how responsive and helpful people are here.