Bela crashes when connecting/disconnecting analog out

hipiers

I am making a sequencer with Bela using the analog outs to control my semi-modular unit. It works fine, my code outputs a looping series of voltages to drive the 1v/oct input via a 3.5mm cable. However when I disconnect the cable from that particular input on my synth and plug it in to something else, Bela crashes, the program stops running and I get the following message in the IDE:

PRU interrupt timeout, -1 110 Connection timed out
PRU interrupt timeout, -1 110 Connection timed out
PRU interrupt timeout, -1 110 Connection timed out
PRU interrupt timeout, -1 110 Connection timed out
The PRU stopped responding. Is the light still blinking? It would be very helpful if you could send the output of the dmesg command to the developers to help track down the issue. Quitting.
PRU interrupt timeout, -1 110 Connection timed out
Makefile:524: recipe for target 'runide' failedmake: *** [runide] Error 1

I assume that the synth is sending a voltage spike to the analog out (or ground) when the jack is plugged in and Bela doesn't like this.

I'm very new to circuit design, how would I go about protecting Bela from these spikes? Or is the issue something else?

Thanks in advance!
P

giuliomoro

This happened to me sometimes when disconnecting an external device. I think the fix could be to keep a ground connection between Bela and the external device(s) at all times. I have not verified that, however. Some analog buffering may also help. There is some code we are working on to automatically recover from such failures.

jarm

giuliomoro is auto recovery from this problem possible now?

I am finding that even with a ground connection maintained at all times (e.g. using breadboard power rails, instead of only wiring between GND, 3v3 and an analog pin), this crash can still occur.

giuliomoro

Kind of ... can you try with this patch?

diff --git a/core/PRU.cpp b/core/PRU.cpp
index c2b1a4137..0faae3d54 100644
--- a/core/PRU.cpp
+++ b/core/PRU.cpp
@@ -671,13 +671,13 @@ int PRU::start(char * const filename, const McaspRegisters& mcaspRegisters)
 {
        switch(belaHw)
        {
-               case BelaHw_Bela:
-                       //nobreak
                case BelaHw_BelaMini:
                        //nobreak
                case BelaHw_Salt:
                        pruUsesMcaspIrq = false;
                        break;
+               case BelaHw_Bela:
+                       //nobreak
                case BelaHw_BelaMiniMultiAudio:
                        //nobreak
                case BelaHw_BelaMiniMultiTdm: