Teensy 3.0 or 4.0 for I2C?


Active member
I have an upcoming project involving some +3.3V I2C parts (DAC and temp sensor at least).
I have an unused Teensy 3.0 I bought a few years ago but, it looks like support isn't great anymore for the 3.0
and am considering buyin a 4.0 instead. Is there any reason to do so? Am I overthinking it and stay with the 3.0?
A Teensy3.0 is perfectly capable of doing I2C transactions. There is still a lot of support and knowledge on this forum.
But if you want to expand your circuitry/design in the future and need more processing power, or move your project to large quanties of products, a Teensy 4 is the way to go.

Note, you might need 2 pull-up resistors, 1 between SDA and 3.3v and 1 between SCL and 3.3v (the resistors are in parallel with the data pins). Typically 2.2k resistors are used for 3.3v. Typically these days I2C devices have pull-up resistors built-in, but not all devices have it. If you can run the i2cscanner example sketch and it can find the device and doesn't hang then you don't need to add pull-up resistors.

Note, the Teensy 3.0 only has 16K of SDRAM.
Teensy 3 are not available anymore. So at first mistake, you will be forced to switch to Teensy 4.
One thing to keep in mind is that Teensy 4 has 3V3 input/output only, while a Teensy 3 is 5V tolerant in its inputs [but outputs 3V3].

Teensy 3.1 and 3.2 were 5V tolerant.

But Teensy 3.0 was not. Do not apply more than 3.3V, as doing so would risk hardware damage.
I also have a Teensy 2.0 which I have been using for another project.
I was planning on adding the pullup resistors anyway so no problem there. I think I will splurge for a Teensy 4.0 and get a few I2C devices to start playing with. It will future-proof my design a bit more. Thx for the info.