Thank you, working on a Teensy 3.5 (4 panels)

Hello, I write to thank for the great work you do. :smiley:
I ran the RGB_Feature demo on 4 panels of 36x12.
I bought them on AliExpress, if somebody is interested, the link is:

I bought the kit in case I can’t do work with Teensy + SmartMatrix

I connected a panel to a Teensy 3.5, but just flicker and couldn’t get something functional. There I noticed that the Teensy give 3.3V data, silly me. The SmartShield would be the solution, but here at the end of the earth in SouthAmerica (Chile), will take some time get one. So I follow the schematics from the shield and can transform the 3.3V data to 5V data.

I used two 74HTC245 chip, two capacitors and I follow the guide of the SmartMatrixSD

I run first in a protoboard, then I soldered it to a plate giving this result :grimacing:


I tested for two panels on a row, so I have 64x16, then I wanted to make it work the 4 panels. So I edited the code and upload the sketch, the changes were only:

const uint8_t kMatrixWidth = 64;
const uint8_t kMatrixHeight = 32;
const uint8_t kPanelType = SMARTMATRIX_HUB75_16ROW_MOD8SCAN;

The result was awesome :astonished:

Again, thank you very much for the great work.

Best regards from Chile
Álvaro Monares G.

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what hub75 dmd panels are you using? all the ones i have used (hundreds!) all run directly from 3.3v logic fine. They did not require 5v logic.

I have these

JIN is connected to U1 and U2, it seems that U1 and U2 are 74hc245 chips.
UR1,UG1,UB1,UR2,UG2,UB2 the chip is DP50206 (Cant find the chip on google)

Maybe my first attempt directly from teensy has something wrong, but when I use the protoboard I didn’t repeat the error. I will give a try again directly.

I do the 5V logic, because at says

Most panels are compatible with 3.3V signals, but some are not. Starting with V3, the SmartMatrix Shield includes 74AHCT245 buffers for all the signals going to the panel, to boost the signals closer to the 5V level some panels require. If you are seeing flickering or no LEDs lit when driving a panel, you may need to add buffers between the Teensy and panel.

Later I will give another try directly from teensy and see what happens.

Best regards
Álvaro Monares G.

@amonares I’m glad the code’s working for you Álvaro! I agree international shipping can be slow and expensive. I’m thinking about making the next version of the SmartMatrix Shield available through a partner company on Aliexpress, shipping from China. Would that be a better option than the current availability through Adafruit and some of their distributors?

@DMD_king I also had no problems with hundreds of panels with the first version of the SmartMatrix Shield which had no level shifters on it, but some new panels from Adafruit wouldn’t work, and after looking into it, it turns out the 74HC chips that are common on these panels actually need 3.7V for a logic 1. Some of these chips do work with 3.3V depending on the conditions, but it’s not guaranteed. Here’s a reference that shows the voltages required by the different logic families (Vih is the problem parameter for us):

Could be better, for the price maybe, but the time will be the same or even worst?

Best regards
Álvaro Monares G.

Good feedback. Do you get your LED panels from China? What site? I was planning to make it available through a store that sells panels, so you can buy a panel and SmartMatrix Shield at the same time. You would have to buy the Teensy from somewhere else though.

Yes, I bought the pannels on AliExpress the link is on the first message of this post.

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