Sharing row selection DOUT SRs across matrices?

MIDIbox NG
1

Hi TK,

 

Is it supported to have a single shift register provide the row selection signals for multiple matrices that have the same number of rows and the same inverted_sel mode? From another thread, it looks like this is possible, but I just wanted to make sure before having a PCB milled!

 

For example:

DOUT_MATRIX n=1 rows=8 sr_dout_sel1=1 inverted_sel=1 sr_dout_r1=2 inverted_row=0 mirrored_row=0  
DOUT_MATRIX n=2 rows=8 sr_dout_sel1=1 inverted_sel=1 sr_dout_r1=3 sr_dout_r2=4 inverted_row=0 mirrored_row=0  
DIN_MATRIX n=3 rows=8 sr_dout_sel1=1 inverted_sel=1 sr_din1=1 sr_din2=2 inverted_row=0 mirrored_row=0

Thanks,

Sauraen

2

Yes, it works even if the DOUT_MATRIX and DIN_MATRIX control different number of rows - they are always in sync and don’t disturb each other.

At least software-wise. Hardware-wise you have to expect less brightness on the LEDs if no dedicated sink drivers are used.

 

Best Regards, Thorsten.

3

Thanks!
 
I am using dedicated sink drivers, a Darlington array (Mouser 757-TD62083APGON), hence the inverted_sel=1. :slight_smile: Thanks for having the DOUT boards support these too!

4

Hi Sauraen

I compared the two spec Sheets of ULN2803 and TD62083APGON. I use the ULN2803…

Thats very interesting because i coldn’t find a difference beside price. Can you tell me why you selected it? - im just curious…

 

At least in the Swiss Mouser Store the ULN2803A is cheaper… (i assume the prices can vary between countries.)

http://ch.mouser.com/ProductDetail/STMicroelectronics/ULN2803A/?qs=sGAEpiMZZMvAvBNgSS9LqpP7ived4CP2

 

best regards

novski

5

I’m pretty sure I just went to transistor arrays, filtered by quantity = 8, ordered them by price, and picked the cheapest one that was in stock. According to my BOM spreadsheet it was $0.81 (~0.59 euro). But I don’t think it matters which kind of sink drivers very much, I used a bunch of discrete MOSFETs in TO220 packages bolted to a heatsink in my ASIDITY project, and it works fine–but that was because there were around 750 LEDs in the matrix!