Teensy-Arduino adapter shield

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Epyon

Epyon

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Hi everyone!

Just like a lot of you, I'm a big user of Arduino and other OSH (and have been since years). I use them in personal as well as in professional projects. Over time, my projects got bigger and bigger, so I needed more capable hardware. I've tried several powerful Arduino alternatives (Beaglebone, Chipkit, you name 'em), but since I discovered the Teensy 3.0 I'm practically hooked up to it. The only thing was that all my projects use the Arduino shield footprint, while the Teensy is quite smaller.

In stead of redesigning all my projects, I opted to design a Teensy-Arduino adapter shield. This shield does just what it says: seamless connection of the Teensy 3.0 to any Arduino shield.

teensy_arduino_shield_1.jpg
The Teensy-Arduino adapter shield with a mounted Teensy 3.0

Its main features are:
  • Drop-in, pin-to-pin Arduino Rev3 compatible
  • Convert between Teensy and Arduino footprints
  • Interface Arduino 5V levels (logic (bidirectional!) and analog) to Teensy 3.3V level: no need to make any change to existing Arduino projects
  • On board power supply and automatic power supply selection
  • Sinking/sourcing capability of digital pins comparable to Arduino boards
  • Coin cell battery holder for Teensy RTC
You can find more details on this page. The main thing is I wanted to unlock the wealth of different Arduino shields for the Teensy, and add some of the more robust features of the Arduino to the Teensy.

I selfishly designed the board for my own projects, but it hit me it might be useful to others too. I design and fab a lot of boards at my work, so if there's enough interest I might put it into volume production.

For the time being, I'm happy to hear your responses and suggestions to the board. It's still a work in progress, but results up to now have been quite satisfactory :) .

teensy_arduino_shield_3.jpg
The Teensy-Arduino adapter shield running an Ethernet sketch
 
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This is a very nice design. A real Ueber Arduino as opposed to my Frankenduino. I had the same idea with the logic level conversion when I needed one for the I2C bus to connect to my LED shields, but it would not have fit on my already full board anymore.
Please keep posting updates. If you want to test if there is a market for it then start a Fundraiser on Tindie.com. I've been in contact with them in respect for a Fundraiser for my LED shield and they've promised to have the Fundraisers back online within the next two weeks
 
Thx! The components on my board are placed by a P&P robot, so I can use quite small components (0603 or smaller) to make everything fit on the board. However, if I offset the Teensy socket more to the right (so the micro USB connector isn't blocked by the Arduino ICSP), things will become more troublesome. I'm therefore thinking of reversing the socket, so the micro USB connection is on the 'front' of the board, just like a regular Arduino.

I've tested the board with an Ethernet shield, micro SD shield and Xbee shield. I still need to test the I²C performance, because I²C uses open-drain drivers while the level shifters I use are more intended for push-pull applications. But I expect it to work though.
 
I2C performance is the reason why I decided to go with a real bus buffer and on my Frankenduino not just with a level shifter. The i2c_t3 library posted here on the forrum by user nox71 allows frequencies of up to 2.4MHz so the Teensy3 can easily use FM+ frequency of 1MHz. When you use longer cables, however the FM+ spec allows up to 10 times the capacitance than a regular I2C bus. That was important to me because in my biggest lighting system I have about 4m of CAT 5 cable.
 
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Nantonos said:
You have your own P&P robot?
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We work with a local fabbing company which specializes in assembling PCBs for small to medium sized series. I just mail them my Gerbers and receive a fully assembled PCB some time later.

Headroom said:
I2C performance is the reason why I decided to go with a real bus buffer and on my Frankenduino not just with a level shifter. The i2c_t3 library posted here on the forrum by user nox72 allows frequencies of up to 2MHz so the teensy3 can easily use FM+ frequency of 1MHz. When you use longer cables, however the FM+ spec allows 10 times the capacitance than a regular I2C bus. That was operant to
Me because in my biggest lighting system I have about 4m of CAT 5 cable.
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The TXS01 series level shifters should have no problem achieving those speeds. They work with mosfets.
 
It's nice to have a local company with those abilities. I would love to have a little local company within driving distance.
In terms of frequency the TSX0102, for example, is a good choice as it allows I2C frequencies of up to 2 MHz. The TSX0102 uses one-shots instead of "regular" mosfets so you also don't need pull-up resistors! DSScircuits has them on a nice little breadboard friendly PCB for prototyping
With my long cables I wanted to have buffering abilities. The normal I2C spec components only can supply 3ma. FM+ can do up to 30mA, thus the higher allowance for bus capacitance. Not really needed for most applications though.
 
Yes it is. They are also very helpful when it comes to questions or tips & tricks regarding PCB assembly. And quite cheap. Start-up costs aside it's cheaper to assemble the whole prototype PCB in the fab than manually soldering them.
 
Back with an update :) .

I've redesigned the shield a bit so the Teensy micro-USB connector now faces the other side, making it still accessible when mounting a shield that uses the Arduino ICSP header. I also replaced the regular opamps with rail-to-rail versions, which should solve the analog input limitation problems I was having. I removed the battery holder and the 3.3V/5V ref switch, making the shield a 5V shield only. Otherwise, the functionality stays the same.

TeensyshldV2.jpg

The new board is currently at the PCB fab, from where it'll move to the assembly fab. I hope to receive the prototypes in the next two weeks for further testing.
 
Epyon said:
Back with an update :) .

The new board is currently at the PCB fab, from where it'll move to the assembly fab. I hope to receive the prototypes in the next two weeks for further testing.
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Hi, any News on this board?
 
Yes there is actually. The development has been on-hold for a while because I had a lot of other projects on my slate (this board is my friday afternoon project at work ;) ).

Power supply and analog section have been extensively tested and work fine. The TXB08 digital levelshifters however had some problems with undefined states. Apparently you have to pull unused input/outputs high or low, or otherwise the pin floats and noise is injected into the power supply rail.

I'm in the progress of making a final revision to the PCB in order to minimize potential noise problems by users who do not set unused digital pins on the Teensy to output LOW (which pulls it to ground). Then it should be ready to ship!
 
I kinda neglected posting any updates on this board. Writing a PhD ánd running a spin-off company at the same time is taking too much of me I guess :D .

Anyway: there is progress and no progress on the board. I did two things:
  • Making a version without the level shifters
  • Making a Teensy board in the Arduino form factor

I started with the first option because the level shifters were too unstable (when not all the input pins were at the same voltage, sometimes the output pins would float) and the T3.1 has 5V tolerant inputs now. But then I shifted to the second option because it would be cheaper to just buy a board with the Teensy 3.1 chip already on board in stead of having to buy a Teensy board and then this adapter shield.

I finished working on the designs this week, and I expect to send it to the fab this coming week. So expect some updates the next few weeks!
 
Epyon said:
Back with an update :) .

I've redesigned the shield a bit so the Teensy micro-USB connector now faces the other side, making it still accessible when mounting a shield that uses the Arduino ICSP header.
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Is there any possibility of using a mini-USB connector instead of the micro-USB connector. Those micro-USB connectors just don't last long with repeated plugging/unplugging. I'm having problems getting two devices charged sometimes, because the micro-USB connectors on the devices won't hold the plug in steady, and it's getting worse. One of those devices in my Galaxy Note II.

8-Dale
 
The current version uses a USB-B connector, like the Arduino Uno. In fact, it uses the same footprint and connector locations so it's perfectly compatible with existing Arduino enclosures.

I'm also no big fan of micro-USB, but mainly because I only have a few micro-USB cables and they always get lost :p .

PS: the board will also include the FTDI header as seen on the Arduino Ethernet boards and can be powered through this as well. The motivation for including this header is mainly personal though, because my projects use TTL serial communication a lot and I can easily hook up a serial monitor to the board through this header.
 
Epyon said:
The current version uses a USB-B connector, like the Arduino Uno. In fact, it uses the same footprint and connector locations so it's perfectly compatible with existing Arduino enclosures.
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Excellent!

Epyon said:
PS: the board will also include the FTDI header as seen on the Arduino Ethernet boards and can be powered through this as well. The motivation for including this header is mainly personal though, because my projects use TTL serial communication a lot and I can easily hook up a serial monitor to the board through this header.
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I also use this feature in my projects. I have both 3.3V and 5V FTDI cables with separated socket pins, which makes it easy to connect to just about anything.

8-Dale
 
The OP has a new board, TAX (Arduino-Teensy crossover shield) that he talked about in May on his blog: http://www.epyon.be/2014/05/04/teensy-arduino-crossover-tax-shield/. As far as I know, the boards are not available for general purchase.

There are two other shields that are currently available, to allow a Teensy to be able to use Arduino shields:
 
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