Use SmartMatrix with Audio Shield



I like to set a project with a Teensy 3.5, two 64 x 32 RGB-Panels and the Teensy Audio Shield. We want to use the Display to play text and play a song over the audio shield in order to use it for karaoke.

I achieved to use the displays as 64 x 64 and the audio shield for themselves. I can’t use them simultaneously because they are sharing seven pins.

In order to solve that problem I like to change the pins used by the SmartMatrix library to unused pins on the teensy 3.5 (unused PWM-Pins are 29-30 and 35-38). Unfortunately the pin assingment (GPIO_PIN_XX_TEENSY_PIN) in MatrixHardware_KitV1.h seems to have no effect.

Has someone else used this combination or does someone know how to change the pin assignment?

Kind regards


Hi Franz, most of the pins used by SmartMatrix are fixed and cannot be moved. I did try to make the pinout as compatible with the audio shield as possible, though you may have to cut and jumper some pins. I don’t know if this will work for your application, and I’ve never tested this feature. There are some details in the V4 schematic which you can find on GitHub. Please post back with questions or if you get it to work.

  • Louis


Hi Louis,

I’m not sure which pins i have to cut and jumper. I can use the audio shield without the pins for the memory chip, the sd card and the volume pot (6, 7, 10. 12. 14, 15). But I do have still pins 9, 11, 22 and 23 which are shared with the RGB-Panel. Can I use these pins simultaneously (connect both devices on same pin)? If not, can you give me any hint how to use other pins for audio shield or SmartMatrix?

At the moment I have only a test setup. Shall I attach a picture?

Kind regards


I’m traveling without my laptop, so I can’t help much right now. Check the teensy datasheet to see if some of the I2S signals used by the shield are available on other pins that don’t conflict with SmartMatrix. The teensy forum may help you move the pins. The cutting and jumpering is likely unnecessary as that fixes a conflict with the APA circuit, not the hub75 matrix.


I’m back in front of my laptop, and I’m not seeing the conflicts. With SmartMatrix Shield V4, pins 9, 11, 22, and 23 are free:

Are you perhaps looking at the older V3 or earlier pinout?


Hi Louis,

thanks for your reply. There seems to be a misunderstanding. I use the Audio Shield and not the SmartMatrix Shield. I connected the RGB Matrix direct to the Teensy because the SmartMatrix Shield is hard to get in germany.

Using the SmartMatrix Shield and the Audio Shield indeed looks better. But they still share pin 13. I already asked for help at teensy forum but didn’t get any help yet.

Kind regards


You can make your own circuit following the SmartMatrix Shield V4 schematic, using DIP parts on a perfboard, if you need a custom form factor. V4 of the SmartMatrix Shield adds an external latch which is used to free up the ADDX pins so they can be used for other purposes (like connecting to the Audio Shield). I’m not sure if the Audio shield and SmartMatrix Shield can be easily plugged in together.

Can you send me a link to the Teensy forum post?

The conflict on pin 13 is between the APA102 LED driver and the Audio shield. I don’t think you’re using the APA102 LED driver, so there shouldn’t be a conflict.


Hi Louis,

thanks again. Here is the link to the PJRC forum. But it’s basically the same text:

I just found a german retailer selling the Smart Matrix Shield V4. So i will give it a try.

You’re right i’m not using the APA 102 LED driver, so maybe both shields together are going to work fine.

I will answer as soon as i tested it.

Kind regards