It was only last August that PJRC released Teensy 4.0. At that time, the 4.0 became the fastest microcontroller development board on the planet, a title it still holds as of this writing — or, well, not exactly. Today the Teensy 4.1 has been released, and using the same 600 MHz ARM Cortex M7 under the hood, is now also the fastest microcontroller board. What the 4.1 brings to the table is more peripherals, memory, and GPIOs. While Teensy 4.0 used the same small form factor as the 3.2, Teensy 4.1 uses the larger board size of the 3.5/3.6 to expose the extra goodies.
The now slightly older Teensy 4.0 — released on August 7th of last year — is priced at $19.95, with the new 4.1 version offered at $26.85. It seems that the 4.1 isn’t intended as a replacement for the 4.0, as they serve different segments of the market. If you’re looking for an ultra-fast affordable microcontroller board that lives up to its Teensy name, the 4.0 fits the bill. On the other hand, if you need the additional peripherals broken out and can afford the space of the larger board, the not-as-teensy-sized 4.1 is for you. How big is it? The sample board I measured was 61 x 18 mm (2.4 x 0. 7″), not counting the small protrusion of the micro-usb jack on one end.
Let’s have a look at all the fun stuff PJRC was able to pack into this space.
100 MBPS ETHERNET
The big news is that Teensy 4.1 comes with 100 Mbps Ethernet support. To use the Ethernet port, you need to supply external magnetics and an RJ-45 jack. These were left off the board for obvious reasons — even using a jack with integrated magnetics (magjack), it wouldn’t fit on the PCB. Instead, a 6-pin header on the board can connect to an external interface. This also helps keep the price low for those who need the other features of the 4.1 without Ethernet connectivity.
PJRC will likely sell a DIY kit of the required parts in the future, but they don’t have a release date or pricing yet. For now, you can easily build your own using this OSH Park shared project. The parts list is in the project’s description, with the key part being the magjack, which will set you back around $2.55 in single quantities. Those building a board should note that this is an early version, and it turns out that only the 0.1 uF capacitor is necessary. Paul Stoffregen of PJRC told me that he just received a simpler PCB for testing, and will publish the design once it’s has been thoroughly verified.
The Ethernet port is capable of full 100 Mbps speed and supports the IEEE 1588 precision time protocol, which allows synchronization of clocks to within 100 ns over wired connections, enabling some very interesting possibilities. But, aside from that, just the inclusion of Ethernet on a microcontroller board is a big deal. Before this, you basically had two choices if you needed this kind of connectivity: use a powerful single-board-computer like a Raspberry Pi with all the latency and headaches the required operating system brings for doing low-level or real-time tasks, or add a slow SPI-interfaced Ethernet board to an existing microcontroller. Instead, you can now use the 600 MHz Cortex-M7 on this new board to run high-bandwidth, low-latency embedded applications without fighting an OS.