How many GPIO pins can be used for internal interrupts (Teensy 4.1)

G

ghostdzog1

Active member
Hello. I am still fairly new to teensy, as well as prototyping, so please forgive me for my lack of experience / understanding.

I am interested in using Teensy boards as the brains for my DIY Hardware MIDI control surfaces.
I am aware that the Teensy boards are great for this purpose for many reasons, including having a fair amount of GPIO pins to connect sensors to (sensors such as rotary encoders, potentiometers, buttons, ribbon controllers etc).

I have a teensy 4.1 (received in the post today).
I am now curious to learn how many of the GPIO pins I can use with internal interrupts.

I thought the Teensy 4.1 had 55 GPIO, however on the pin out I can not see all the GPIOs.
Perhaps I am not looking hard enough. Can someone tell me where the 34 - 41 GPIO's are? Perhaps its just me, but these pins don't appear to exist.

If pins 34 - 41 (8 pins) do not exist, then, does that mean that the Teensy 4.1 has 47 GPIO? And if so (either way)
how many of the GPIO pins can be used as internal interrupts?

Please help ;-)
Thanks for reading :confused:
 
ghostdzog1 said:
Hello. I am still fairly new to teensy, as well as prototyping, so please forgive me for my lack of experience / understanding.

I am interested in using Teensy boards as the brains for my DIY Hardware MIDI control surfaces.
I am aware that the Teensy boards are great for this purpose for many reasons, including having a fair amount of GPIO pins to connect sensors to (sensors such as rotary encoders, potentiometers, buttons, ribbon controllers etc).

I have a teensy 4.1 (received in the post today).
I am now curious to learn how many of the GPIO pins I can use with internal interrupts.
Click to expand...
I believe all of the pins that take digital inputs on the Teensy 4.1 can be used for interrupts. IIRC, only the Teensy LC had restrictions on which pins could be used for interrupts. Note on other Teensies, there are some pins that can be used for analog inputs that cannot be used for digital inputs (or interrupts).

ghostdzog1 said:
I thought the Teensy 4.1 had 55 GPIO, however on the pin out I can not see all the GPIOs.
Perhaps I am not looking hard enough. Can someone tell me where the 34 - 41 GPIO's are? Perhaps its just me, but these pins don't appear to exist.
Click to expand...

If you look at the pinout card for the Teensy 4.1, and orient the card so the USB micro-B is facing up, pins 33-41 are the bottom 8 pins on the right side (next to the micro-SD card reader).

If you look on the back of the pinout card, you will see that pins 42-47 are provided in the micro SD card reader. You could access these pins with pcb that provides the micro SD card interface and brings out the pins.

There are two sets of memory solder pads underneath the Teensy (directly under the micro SD card reader) for soldering one flash chip and up to 2 psram chips that have pins 48-54 (the flash chips are non-volatile memory, the psram chips give you more memory though it is slower than the main memory). If you don't solder flash/psram, then you could solder wires to access these pins.

There are 5 pins on the inside that are next to the micro SD card reader. These are not gpio pins, but provide on/off, program, ground, 3.3v, and power for the real time clock. Unfortunately, I don't see these pins listed on the pinout card, but they are the same as the pins on the Teensy 4.0.

There are 5 pins on the left side (with the USB facing up) that provide the USB host capability. These do not provide digital input/outputs.

There are 6 pins on the right side (with 2mm pitch, instead of 2.54mm) that provide the ethernet support. These do not provide digital input/outputs.

Here is the online version of all of the pinout cards:

ghostdzog1 said:
If pins 34 - 41 (8 pins) do not exist, then, does that mean that the Teensy 4.1 has 47 GPIO? And if so (either way)
how many of the GPIO pins can be used as internal interrupts?

Please help ;-)
Thanks for reading :confused:
Click to expand...
See above. Maybe you were confusing it with the Teensy 4.0 which only has 39 pins (including the pins for attaching a micro SD card reader, and 10 solder pads).
 
Last edited:
MichaelMeissner said:
I believe all of the pins that take digital inputs on the Teensy 4.1 can be used for interrupts. IIRC, only the Teensy LC had restrictions on which pins could be used for interrupts. Note on other Teensies, there are some pins that can be used for analog inputs that cannot be used for digital inputs (or interrupts).

If you look at the pinout card for the Teensy 4.1, and orient the card so the USB micro-B is facing up, pins 33-41 are the bottom 8 pins on the right side (next to the micro-SD card reader).

If you look on the back of the pinout card, you will see that pins 42-47 are provided in the micro SD card reader. You could access these pins with pcb that provides the micro SD card interface and brings out the pins.

There are two sets of memory solder pads underneath the Teensy (directly under the micro SD card reader) for soldering one flash chip and up to 2 psram chips that have pins 48-54 (the flash chips are non-volatile memory, the psram chips give you more memory though it is slower than the main memory). If you don't solder flash/psram, then you could solder wires to access these pins.

There are 5 pins on the inside that are next to the micro SD card reader. These are not gpio pins, but provide on/off, program, ground, 3.3v, and power for the real time clock. Unfortunately, I don't see these pins listed on the pinout card, but they are the same as the pins on the Teensy 4.0.

There are 5 pins on the left side (with the USB facing up) that provide the USB host capability. These do not provide digital input/outputs.

There are 6 pins on the right side (with 2mm pitch, instead of 2.54mm) that provide the ethernet support. These do not provide digital input/outputs.

Here is the online version of all of the pinout cards:


See above. Maybe you were confusing it with the Teensy 4.0 which only has 39 pins (including the pins for attaching a micro SD card reader, and 10 solder pads).
Click to expand...

Hello Folks
Thanks for your help on this. I think I must have been looking at the wrong pinout diagram. Now, when I look, I can clearly see the pins I mentioned that I thought didn't exist.

Well, if all the pins with grey numbers beside them are digital pins, then that would be great. As that should allow me to have enough interrupt capable pins to allow me to connect the number of channels I want without having to use too many gpio expanders. Well at least for my first experiments in midi controller design,

Thanks again
really appreciate it.
 
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