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Repurposing V4L Board


jab

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Hey guys - I'm looking at repurposing my V4L board as a plain old button/led matrix and wanted to double check with you folks before I break something. After studying the schematic (http://www.ucapps.de/midibox_seq/mbseq_lite_blm.pdf) it seems like I should be able to make some custom cables to connect this to a DIO_matrix module. Here's what I concluded:

J5A/J5B A0-A7: connect to DOUT #1 O7-O0
J15A D0-D7: connect to DOUT #2 O7-O0
J15A Vs: connect to Vs
J10 D0-D7: connect to DIN #1 I0-I7

Anyone see any issue with this? Or is there a better way to do what I'm after?

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  • 2 weeks later...

So I got around to testing this out... wired up as I explained above, using the following in my NGC file:

DIN_MATRIX  n=1  rows=8  inverted_sel=1  sr_dout_sel1=1  sr_din1=1
DOUT_MATRIX n=1  rows=8  inverted_sel=1  sr_dout_sel1=1  sr_dout_r1=2

EVENT_BUTTON_MATRIX id=1  fwd_id=LED_MATRIX:1  type=NoteOn key=36 lcd_pos=1:1:2 label="Matrix1 Pin %2p %b"

So with this code (for testing only) I noticed that when i push a button, the button's LED lights fully (as expected) but the LED in the same column, but one row above also lights faintly.

i've double checked all my wiring and can't find anything wrong. My SEQ_V4L always worked perfectly so I feel confident in my soldering, but... Any suggestions on what to test?

 

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Does it make a difference if you replace the 8 100 ohm resistors by 220 ohm?

100 Ohm has been selected in the original circuit since the LEDs are driven from 3.3V pins - but in your case they are driven from 5V pins which could lead to these ghosting effects.

Best Regards, Thorsten.

 

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I don't see a schematic for the SEQ v4 lite. But one trick I found for the BLM is that Schottky diodes from the base to collector help to turn off transistors faster and can reduce ghosting on the current sink side. Also in my case there are 10k resistors from the base to the emitter to reduce power draw, and to provide a current path if the base is ever in a high impedance state.

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