Teensy 3.5 is based on the 32-bit 120MHz ARM Cortex-M4 processor with floating point unit. All digital I/O pins are 5V tolerant. It is formatted into a compact ‘teensy’ board outline for easy embedding into projects or for use with solderless breadboards. Perhaps best of all, it is compatible with the popular Arduino IDE programming environment as well as many of the existing Arduino libraries, so it is very easy to get up and running unlike many other advanced microcontrollers that are available.
- Teensy 3.5
- 1×24 (x2) male headers selectively plated with gold contacts and tin solder pins
- Handy pinout diagram
KEY FEATURES OF TEENSY 3.5:
- MK64FX512VMD12 ARM Cortex-M4 running at 120MHz.
- 256K RAM
- 512K FLASH
- 4K EEPROM
- USB host pins
- Micro SD Socket
- 1 USB port with 480 Mbit/sec, can be any device type
- 10/100 Mbit Ethernet
- 1 CAN Bus
- 2 I2S Digital Audio
- 3 SPI, 1 with FIFO
- 3 I2C up to 1 Mbits/s
- 6 serial ports, 2 with FIFO
- 16 general purpose DMA channels
- 20 PWM capable pins
- 58 digital I/O, all interrupt capable
- 40+2 breadboard friendly I/O pins
- 27 analog input pins with 2 13-bit (usable) ADCs on-chip
- 2 analog output pins with 12-bit DAC resolution.
- Cryptographic Acceleration
- Random Number Generator
- Built-in RTC for date/time
- FPU hardware
- Compatible with Arduino IDE and many libraries
- Works with Windows, Mac OS X and Linux
- Small size is perfect for embedding or use with solderless breadboards
- 5V tolerant digital I/O
- 3.3V operation
The Teensy product line which is focused on being fast , small and Arduino compatible is developed by the company PJRC. They have a loyal following of designers and advanced hobbyists that create many libraries to take advantage of some of the more advanced features of the Teensy products or to modify Arduino libraries for compatibility. Many of them also participate in the excellent PJRC forum. The forum is targeted towards more advanced users and topics.
The Teensy 3.5 is very fast compared to standard Arduino products but not nearly as fast as the Teensy 4.x. What the Teensy 3.5 mainly brings to the party compared to the Teensy 4.1 is 5V tolerance on the I/O which removes the need for possibly dealing with logic level converters and makes it a little more fool-proof than the 4.x line.
It also has a a nice selection of I/O that includes 2 12-bit analog outputs that the Teensy 4.x lacks. It is a great choice for someone looking to move up in performance from something like a Mega 2560 or are getting started with microcontrollers in general and looking for a more capable microcontroller than a typical Arduino.
Getting Started with Teensy
Install Arduino IDE Software
To program the Teensy using the Arduino IDE, you must first have the IDE installed if it is not already. If it is installed but not the current version, now is a good time to update to the latest.
Be sure to use the downloaded version of the Arduino IDE which can be downloaded at: https://www.arduino.cc/en/main/software
Install Teensyduino Software
Teensyduino is the name of the PJRC software that adds features and libraries that support the Teensy boards on the Arduino IDE. Support is available for Windows, Mac OS X and Linux.
The download and installation instructions can be found at: https://www.pjrc.com/teensy/td_download.html
When Teensyduino is running which it should do automatically, a small window is opened on the desktop. This is the Teensy Loader application that handles the actual download to the Teensy board. Most of the time you can ignore this window as it defaults to Auto Mode which means it will take care of automatically downloading to the Teensy without needing to press the Teensy Program button, but it does need to be running in order to download to the Teensy boards.
Running Blink Program
Once you have the software installed, running the venerable ‘Blink’ program that blinks the on-board LED every second is no harder than a typical Arduino.
- Attach a Micro-B USB cable to the Teensy
- In the IDE select Tools / Board / Teensyduino / Teensy 3.5
- USB Type should be set to ‘Serial‘
- Select the COM port the Teensy 3.5 is on.
- Open Examples / Basic / Blink
- Press the upload button
The Teensy 3.5 has the on-board LED attached to pin 13 like a typical Arduino.
If the setup is correct, the software will compile and download to the Teensy. The onboard LED should start blinking once per second. Since the board will already have Blink installed when you receive it, you might want to change the timing of the blink to verify the new download was successful.
Important information before going further with using Teensy 3.5
I/O is 3.3V but 5V Tolerant
The Teensy 3.5 operates at 3.3V internally and when driving digital outputs will output a 3.3V signal. This is typically fine for most 5V peripheral devices to detect a logic HIGH level. Digital input levels coming from 5V peripherals will not damage the chip.
The analog inputs still need to adhere to the 3.3V limitation. This includes A10, A11, A21, A22, A25, A26, AREF, Program and Reset
If you need a Teensy in a smaller package that is 5V tolerant, the Teensy 3.2 may be a good choice to consider.
Power – One Power Source at a Time!
The Teensy 3.5 can be powered one of 3 different ways, but it is important to note that these are mutually exclusive unlike typical Arduino boards. Internally the module does not provide any power switching between the different power inputs. In essence, if you hook up two different power inputs such as through the USB cable and also through the VIN pin, those two power sources will be shorted together.
USB power (VUSB) – This is typically 5V supplied through the USB cable. A solder pad next to the USB connector also connects to the same VUSB power. An on-board regulator provides 3.3V to power the module
The Teensy 3.5 can also act as a USB Host and supply 5V power coming in on the VIN power input or VUSB pin out the USB port.
VIN pin – External power of 3.6V to 6V can be applied to the VIN pin which also powers the on-board 3.3V regulator to power the rest of the module.
3.3V pin (x2) – These are normally used to power 3.3V peripherals. Total current should be limited to less than 250mA to avoid overheating. Also if you draw too much power and cause the 3.3V to dip down around 3.0V, the CPU will reboot.
External power of 3.3V can also be applied to the 3.3V pins. This bypasses the on-board regulator and powers the module directly. This is the least desirable way to power the module as it bypasses some of the power protection circuitry.
The most likely way to run into trouble with power is by having the Teensy normally powered through VIN and then deciding to hookup the USB cable to download new code without disconnecting VIN first.
If it is desired to separate the VSUB and VIN power inputs, there is a trace between two large solder pads that can be cut as shown here. If the module is normally powered through VIN, this prevents the USB power from also connecting to the board.
A USB cable can be modified by cutting the red 5V power wire inside cable, but an easier/cleaner solution is to get a USB Micro-B cable that has both data lines and a DC power switch as shown below.
You can find the link to the full cable information at the bottom of this page or click on the pic.
Misc Bits of Info
The USB port on the Teensy 3.5 has significant functionality not available on a normal Arduino. For most standard applications it should be set to the default “Serial” mode which is how it works with an Arduino. If you have problems connecting to the Teensy, check this setting.
A quick scan of the menu options available gives an indication of the flexibility of the USB port on Teensy 3.5.
The connector used is the standard Micro-B USB. As with any boards that use this small connector, use care to push/pull the cable directly in and out of the connector and not apply pressure upwards in a lever motion to avoid possible damage.
The button on a Teensy board is not a typical reset button like on an Arduino. When pressed, the program button causes the Teensy to enter ‘Programming Mode” where it waits for a download over USB. If the Teensy is connected to the IDE via a USB cable, the last program will automatically be downloaded again and ran.
If the program button is pressed and held for about 15 seconds, the red LED will flash. When the button is then released, the FLASH memory is fully erased and a known good LED blink program is restored into FLASH memory and starts to run. This is a handy way to help restore an otherwise bricked module due to an errant program.
CPU Speed Selection
The Teensy 3.5 nominally operates at 120MHz.
You can select a lower speed to operate at, down to 2MHz, mainly for power sensitive applications. On the other hand you can also potentially overclock the CPU up to 168MHz if adequate heat sinking is provided. Keep in mind that the parts on the board are graded for 120MHz, so performance at clock speeds above that cannot be guaranteed.
Take note that USB will not work at clock speeds of 16MHz or less! It is highly recommended not to drop the clock lower than 24MHz unless you are prepared to work without USB.
The Teensy CoreMark benchmark page has some excellent information on performance, current and temperature over different operating frequencies.
Adding an Audio Adapter
Due to the strong processing power available in the Teensy products, they are a popular target for audio projects whether it is playing multiple WAV files simultaneously, synthesizing music or building sound reactive projects. The Audio Adapter 3.x (Rev C) is designed for the Teensy 3.x product line and supports high quality 16-bit 44.1kHz sample rate (CD quality) audio.
You can find the link to the full Audio Adapter information at the bottom of this page or click on the pic.
Assembling the Module
The board ships with high quality selectively plated male headers that are hard to find. They have gold plating on the contact portion of the leg while the solder pins are tin plated for easiest soldering.
The board ships with the male headers loose. This provides maximum flexibility depending on how the board will be used or they can be replaced with other types of connectors such as female headers.
To ensure good alignment during soldering first insert the loose headers into a solderless breadboard. The board can then be placed on top of the headers and easily soldered in place.
If you want to socket the Teensy 3.5, it can be mated with these 24-pin female headers.
For the vertically challenged, we also offer this complete set of high quality, low profile headers to minimize the stacking height.
Note: Some pics may show the headers unsoldered for mock-up, but the headers must be soldered to make electrical connections.
Our Evaluation Results:
The Teensy line of boards are an excellent product that provides high performance and advanced I/O to tackle even the hardest problems which is why they are often found in advanced hobbyist projects as well as low volume production builds.
The PJRC forum provides access to excellent technical advice that is far more advanced than found on the normal Arduino forums. It is the best place to find information on how to use the advanced features found in the Teensy. It is not the place to get basic Arduino type questions answered however, which is good as the forum is not cluttered with ‘how do I blink an LED?’ type questions.
The Teensy 3.5 is a good solid performer in the middle of the Teensy performance spectrum. If you are brand new to Arduino and programming, you might consider getting your feet wet with a standard Arduino clone board like the Uno or Mega 2560 first.
There are some other Teensy products that may be better suited depending on the application. The Teensy 4.1 has a similar I/O arrangement but has significantly higher performance and more memory. The Teensy 3.2 maintains the 5V tolerant I/O in a smaller package and runs at 72MHz which is still blistering fast compared to a typical Arduino.
It is highly suggested to checkout the PJRC website and forum at the links below for additional information.
Before they are shipped, these modules are:
- Tested by PJRC
- Packaged in high quality resealable ESD bag for safe storage.
PJRC Forum – Excellent source of technical information
PJRC website – Good source of information with many example applications in blog posts.
Board Schematics – Scroll down for different schematics.
|Microcontroller||NXP MK64FX512VMD12 ARM Cortex-M4F|
|Clock Speed||120MHz nominal (Optionally 2MHz to 168MHz w/ cooling)|
|Pin Current Output||10mA|
|I/O Logic Levels||3.3V|
|5V I/O Compatibility||Yes on digital I/O|
|DC Current that can be drawn from 3.3V Pin||250mA maximum|
|Operating Voltage||3.6 – 6V on VIN or VUSB pin|
|Typical Operating Current||50mA typical @ 120MHz|
|Built-in LED||Attached to digital I/O Pin 13|
|USB Connector Style||Micro-B Female|
|Board Dimensions (PCB)||61 x 18mm (2.4 x 0.7″)|
|Reference Manual||NXP MK64FX512VMD12 reference Manual|