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Visualizer parts?

Posted: July 8th, 2015, 10:53 pm
by unfrostedpoptart

I just got the Mojo plus a couple of proto boards and the Visualizer board. I'm doing a lot of great stuff with it but have some questions going forward.

The Visualizer board is great but eats virtually all the FPGA I/Os on the connectors. I used an extra proto board and connectors as an interposer to disconnect the RTC, light sensor, mic, etc. I also had an idea to free up another 24 pins by paralleling the R, G, and G pins of the LED matrixes and treat it as a single 8x16 display. However, when I tried this, I found out that the LEDs are mounted so the common anode pins are the vertical/row direction making this impossible without somehow rotating the displays my 90ยบ. Wouldn't the board have been more useful with the anodes across as columns?

Anyway, I'm now thinking of remounting the displays on a larger proto board oriented the correct way. However, I don't have the tools to remove/move the SMT power FETs or the resistor packs. The schematic PDF doesn't show a part number or spec for these. Can someone tell me what they are so I can get through-hole equivalents?

I read 151 and 111 on the resistors which I thought would be 110ohm and 150ohm. However, that would seem to give too big a voltage drop from 3.3volts for the forward voltage of the LEDs (2.2v red, 3.3v green & blue I think - from 2088RGB datasheet). LED drivers are some kind of p-channel power MOSFET. I found this part which I think would work for 5 at a time: ... _ds_en.pdf

Thanks for any info!


Re: Visualizer parts?

Posted: July 10th, 2015, 2:29 pm
by embmicro
Hey David,

You could still treat the display as a single 8x16 even with common rows. You would just like up half a row at a time. You can scan one then the other or alternate between them. The effect would be exactly the same as common columns, but perhaps just a little less intuitive when you do the multiplexing setup. The reason we didn't do that is because each display will be dimmer as it will be on half the time it will be if you drive them individually. This may not be an issue for you.

Here are the P/N for the resistors and MOSFETs
R1, R3, R4, R6 Red/Blue resistors 8 CRA6P8110CT-ND
R2, R5 Green resistors 4 CRA6P8150CT-ND

The PN are for Digikey and the resistors are 110 and 150 ohm.

I hope this helps!

Re: Visualizer parts?

Posted: July 10th, 2015, 3:19 pm
by unfrostedpoptart
Thanks Justin!

Great info. I'm already working on converting led_display and led_driver. Think I'll drop to 4 bits per color too. If it doesn't look good, I'll place yet another Digikey order :)

Also, just to check, in led_display, I think x,y = 0,0 is the upper left corner. Correct? I was going to use your number_rom and add a few letters. Has anyone already created a (semi)full ASCII version of the ROM?


Re: Visualizer parts?

Posted: July 28th, 2015, 5:48 pm
by embmicro
I haven't looked at the ROM in a while but 0,0 should be the upper left corner. I don't know of any full ROMs, but it wouldn't surprise me if there was something similar out there.