Core 32 J8/J9 strangeness

Testing/Troubleshooting
1

Hi all,

While preparing to finish my upgrade to MBSEQv4 I have found a strange problem on my Core32 board. Currently I have my SDCard working, LCDs working, external power ready. But when I hooked up my DIN/DOUT boards they seem to not be working correctly. I got the same behaviour with or without a customised HWConfig file on my SDCard.

After lots of following cables and making sure I have the SC/RC/SI/SO lines connected correctly, I tried checking the Core32 J8/J9 connector to make sure R31 (the 4x220 Ohm SIL resistor) is working correctly. I found that something was very odd, I could measure 30k resistance between VS and SC/RC/SI/SO!

I removed the SIL resistor and found I have no resistance on the SC/RC/SI/SO lines.

I tested the SIL resistor now that I have removed it and it seems fine i.e. 220 Ohms from the dotted pin to each other pin.

Before I install a new 220 Ohm SIL resistor, I would like to ask if it would be worth trying the connection to my DIN/DOUT boards without the 220 Ohm SIL resistor installed? Or should I just install the new one and see what happens with that one?

Thanks in advance for any help.

David

2

did´cha install the arnold?

3

did´cha install the arnold?

Err I’m not sure if I understand? Arnold?

4

terminator :slight_smile:

5

Hi,

the DIN/DOUT modules cannot be controlled without pull-up resistors, because pins are working in Open Drain mode, which means that they are switching between Vss (for logic-0) and high-impedance (for logic-1)

I could measure 30k resistance between VS and SC/RC/SI/SO

Nothing to be worried about, you measured the resistance between VS -> any other component (e.g. chips) -> VD -> pull-up resistor

The path between Vd->SC/RC/SI/SO is the interesting one.

It would be interesting what you mean exactly with “they don’t work correctly” - what is the effect?

Are they not working at all (no LEDs enabled, no button event regognized), or do they behave randomly? Are LEDs even flickering, and/or do buttons trigger the wrong functions?

Best Regards, Thorsten.

6

terminator :slight_smile:

Aha :slight_smile: but terminate what? The DIN/DOUT chain? If so then can you point me towards where this is described, I don’t see it anywhere on ucapps.de… is this a new thing? My DIN/DOUT chain has been working as is for over 3 years now.

7

the missing termination is probably not the reason for your trouble, but it is documented here: http://ucapps.de/midibox_seq/mbseq_v4_din.pdf

8

Hi Thorsten, thanks for the info.

the DIN/DOUT modules cannot be controlled without pull-up resistors, because pins are working in Open Drain mode, which means that they are switching between Vss (for logic-0) and high-impedance (for logic-1)

Ok, I had a feeling this was probably not too helpful. I’m a bit stuck and I was trying to come up with other things to test :slight_smile:

Nothing to be worried about, you measured the resistance between VS -> any other component (e.g. chips) -> VD -> pull-up resistor

Aha, from memory I think there was also resistance between some of the SI/RC pins, but I forget exactly which.

The path between Vd->SC/RC/SI/SO is the interesting one.

So I will install R31 again and test exactly where I was measuring the resistance tonight.

It would be interesting what you mean exactly with “they don’t work correctly” - what is the effect?

Are they not working at all (no LEDs enabled, no button event regognized), or do they behave randomly? Are LEDs even flickering, and/or do buttons trigger the wrong functions?

Well, to be more specific each time I turn on, a random set of LEDs is lit. No buttons on my front panel or encoder seem to make any difference i.e. I cant change any parameters on the LCD and the GP buttons do not toggle LEDs on or off.

I guess my next step is to put R31 back and post here exactly which pins have the resistance. Any other suggestions?

Edit: update is that with R31 back in, on the Core32 board J8/J9 (with nothing else plugged in) I can measure 220 Ohm from VD to SC, RC and SO. But nothing on SI. I checked and the IDC socket SI pin is definitely soldered correctly, so I guess it must be something between the SI pin and the R31. Any ideas what could cause it?

Cheers

David

9

the missing termination is probably not the reason for your trouble, but it is documented here: http://ucapps.de/midibox_seq/mbseq_v4_din.pdf

Ok, now I know what you mean :smiley: I must admit I don’t have the termination on either chain, I know it was recommended at one point with MBSeq3, but I had already put mine in the box by the time I realised! I will give it a try tomorrow though, thanks for the pointer.

Hasta la vista!

David

10

Hurrah, I have got the DIN and DOUTs working perfectly now. Silly me, I had mixed the SC and RC lines :blush:

I will reply to myself just to finish this off.

Edit: update is that with R31 back in, on the Core32 board J8/J9 (with nothing else plugged in) I can measure 220 Ohm from VD to SC, RC and SO. But nothing on SI. I checked and the IDC socket SI pin is definitely soldered correctly, so I guess it must be something between the SI pin and the R31. Any ideas what could cause it?

There should not be any resistance on SI, I should have double checked the schematic before posting. Still making noobie mistakes after 8 years here, ah well :hmm:

Case closed!

Cheers

David