Teensy Quick Reference: Code Examples, Tips and Tricks

JBeale · Mar 19, 2014

Headroom · Mar 19, 2014

Very nice! This should by all means be a sticky thread!

Paul · Mar 19, 2014

Headroom said:
This should by all means be a sticky thread!

Done.

PaulStoffregen · Mar 19, 2014

I'm pretty sure it's going to get cluttered, but John will be editing the main message.

If there's a desire to have the clutter deleted, maybe like once a week, John can send a request to me or Robin. Actually best to send to Robin... she does most of the daily behind-the-scenes forum maintenance that nobody sees, mostly deleting and banning the spammers who get through the human verification but lurk for weeks or months before spamming, in hopes of evading "new user" filters.

JBeale · Mar 19, 2014

Suggestions welcome! I don't have enough time or attention span to cover the big and rapidly growing world of Teensy by myself. You could post your suggestion here; and I could copy it into my top post. If overlong threads are really a problem, you could delete your own post (can you?) or I could delete it (if Paul's OK with that). Or we could have a second separate thread just for suggestions.

But if I can keep things updated, most people can freely ignore the remainder of the thread posts- or go looking through them, if interested, or to find something I missed, etc.

I see the list as having two main purposes, (1) as reference, quickly find that useful bit of info/code you need but couldn't find, and (2) as inspiration; examples of what others are doing with Teensy that you might not have considered.

nox771 · Mar 19, 2014

High-speed I2C library (Wire & Wire1): http://forum.pjrc.com/threads/21680-New-I2C-library-for-Teensy3

ADC library: http://forum.pjrc.com/threads/24399-quot-Complete-quot-implementation-of-Teensy-3-0-ADC-as-a-library

Eclipse: http://forum.pjrc.com/threads/1474-Anyone-using-Eclipse-for-development

MAC Address: http://forum.pjrc.com/threads/91-teensy-3-MAC-address

Optimizing build size: http://forum.pjrc.com/threads/25196-How-to-get-a-little-bit-more-FLASH-room-on-Teensy-3-x

Software reboot: http://forum.pjrc.com/threads/24304-_reboot_Teensyduino()-vs-_restart_Teensyduino()

I would include some RTOS links, but I'm not sure what is considered best or most current.

nlecaude · Mar 19, 2014

Artnet to OctoWS2811 : http://forum.pjrc.com/threads/24688-Artnet-to-OctoWS2811?highlight=artnet

stevech · Mar 19, 2014

Is there a way that the additions such as post #6 can be added to post #1 by any user? Or by a moderator for this section?

nox771 · Mar 19, 2014

Here is another one. I would actually rank this as one of the top things I've gotten off the forum. This has to do with when you migrate beyond using comm terminals and start writing your own custom host programs. For working with the comm ports (not HID), web searches generally direct to things like Boost.Asio, libctb, or similar. I've worked with a number of such libraries, and they all have problems (eg. linking in Boost is sort of like linking in the library of congress..)

In this thread: http://forum.pjrc.com/threads/7826-USB-to-digital-I-O-delay
There is a latency test program: http://forum.pjrc.com/attachment.php?attachmentid=149&d=1358182899

It's not a library, and it takes a bit of dirty code extraction, but in the latency_test.c file are transmit_bytes() and receive_bytes() routines which are setup to compile and work across Linux, Mac, and Win systems. The routines are very short, and orders of magnitude easier than trying to get something like Boost going. So in summary:

PC Host communication routines: http://forum.pjrc.com/attachment.php?attachmentid=149&d=1358182899

duff · Mar 20, 2014

Here is another useful post for inline assembly here

linuxgeek · Mar 20, 2014

MicroSD guide: http://forum.pjrc.com/threads/16758-Teensy-3-MicroSD-guide

Something on IntervalTimer would be good, but the posts I saw might be more confusing, since it was about the creation of the library: http://forum.pjrc.com/threads/17543-PITimer-PIT-(Periodic-Interrupt-Timer)-library-for-Teensy-3-0/

MichaelMeissner · Mar 20, 2014

The touchRead function is not documented in the the Teensy library page. The touchRead function does capacitive reading on select pins and it allows you to create switches and analog meters with with nothing but an extra wire (providing you share a common ground with the Teensy). This shows a minimal use for touchRead: http://njhurst.com/blog/01356576041.

On both the Teensy 3.0 and 3.1 chips, the touch sense pins are: 0, 1, 25, 32, 33, A1, A2, A3, A4, A5, A8, and A9

nox771 · Mar 20, 2014

IIRC this one:

Periodic Interrupt Timer Library http://forum.pjrc.com/threads/17543-...or-Teensy-3-0/

has been superceded by IntervalTimer, which is part of core and now has a reference page: http://pjrc.com/teensy/td_timing_IntervalTimer.html
Trying to manually work with PIT might cause problems.

JBeale · Mar 20, 2014

@nox771: Thanks, that's good to know.. I updated again. I find the Teensyduino pages at http://pjrc.com/teensy/teensyduino.html are a little confusing as it's not immediately obvious from the top level what applies to all versions, or just Teensy 2 ,or just T3. In fact the top level doesn't mention Teensy 3 at all, and I assumed it was all old material.

PaulStoffregen · Mar 21, 2014

Maybe add a "frequently asked questions" section?

Here's 2 answers for the price of one (Lock bits and 72 MHz support on Teensy 3.1)

http://forum.pjrc.com/threads/25407-Teensy-3-0-3-1-Lock-Bits-and-Reprogramming?p=44400#post44400

Another frequent question involves whether it's ok to use Teensy in commercial projects. I believe I've answered that several times. Here's a couple of the detailed ones:

http://forum.pjrc.com/threads/799-Firmware-loader-for-Teensy-3?p=1783&viewfull=1#post1783
http://forum.pjrc.com/threads/24063-Paul-Teensy-in-a-commercial-product?p=34451&viewfull=1#post34451

Also, maybe this CAN bus thread would be good to include in the libraries part?

http://forum.pjrc.com/threads/25101-CAN-Bus-Library-for-Teensy-3-1

pictographer · Mar 22, 2014

USB Host
http://www.circuitsathome.com/tag/usb-host-shield
http://forum.pjrc.com/threads/13433-USB-Host-Status

FAQ Candidates:

How do I deal with this 3.3V vs 5V stuff?
How do I control something that needs more current than a Teensy I/O can source?
Why is the reset button sometimes needed and sometimes not?
How do I make a serial connection to a Teensy without the Arduino Serial Monitor? E.g. cu, screen, Putty, TeraTerm, etc.
Are there any full color graphic displays that are easy to use with a Teensy?
What's the cheapest display that's easy to use?
How do I make a custom keyboard from a Teensy? How are the buttons wired? How does the software send keystrokes?
How do I drive a cheap speaker with a Teensy? E.g. switch a transistor using PWM, varying the frequency. Low pass filter. Software. Etc.
What's a good rechargeable battery solution? What kind of voltage regulator? How is the battery wired? Where do I cut? Which way does the diode go? How do I prevent a USB charger from turning itself off?
Is my Teensy dead?
What's the difference between an Arduino and a Teensy in terms of software support?
What's the difference between an Arduino sketch and a C++ program?
What are the popular wireless options for a Teensy and what are the differences between them? E.g. wifi router, bluetooth module, wifi module, 315/433 MHz RF module, XBee module, GSM module, GPRS module.

stevech · Mar 25, 2014

Re: Wireless data radio, HopeRF RFM22 and RF22B modules and the excellent RF22 Arduino/Teensy library for the radio modules.

Relevant to the RF22 library for AVR and Teensy 2,3...
1. See this tread for solution to pin 13, 14 remapping to move SPI SCK to pin 14 so pin 13 can be used as LED. http://forum.pjrc.com/threads/25349-Remapping-pin-13

2. Some RF22 modules have an TX/RX antenna switch (6 pin DIP IC); Radio's GPIO0 and GPIO1 bits control the switch, normally. Some RF22 modules have these two GPIO bits wired opposite (TX/RX) versus others. The #ifdef in the RF22 library is hard-coded with an #ifdef 0 on this hardware specific choice. If wrong on the ifdef, the signals are 40dB too weak (antenna not used). Cure is to put the same code as in the library in the application but change the #ifdef to match hardware wiring of the GPIO bits.
This library code:

Code:

#if 0
    spiWrite(RF22_REG_0B_GPIO_CONFIGURATION0, 0x12) ; // TX state
    spiWrite(RF22_REG_0C_GPIO_CONFIGURATION1, 0x15) ; // RX state
#else
    // Reversed for HAB-RFM22B-BOA HAB-RFM22B-BO
    spiWrite(RF22_REG_0B_GPIO_CONFIGURATION0, 0x15) ; // RX state
    spiWrite(RF22_REG_0C_GPIO_CONFIGURATION1, 0x12) ; // TX state
#endif

can be copied into application and the #if 0 can be #if 1 depending on the hardware. I had RFM22B modules so #if 1 is needed.

Of course, a mix of RFM module hardware types would be messy in terms of this. Each RFM22 (SiLab's 4431 chip) returns a device type code that's in the data sheet for the chip. Mine were type = 8. Others are type 7.
When I get next batch I ordered from a different source, perhaps the type 7 vs. 8 can be used to decide at run time rather than compile time.

Modules with no TX/RX switch (e.g., low TX power) can just skip this code.

These changes made, my radios are working very well. Using the reliable datagram mode (ACKs for every unicast message), with node addressing.

PaulStoffregen · Mar 28, 2014

Maybe links to the many Eagle files/libs people have posted would be good too add?

I personally do not use Eagle, so I'm not qualified to say which ones should be on this post. Maybe some Eagle users could recommend which threads have the best info?

nox771 · Mar 28, 2014

Hmm.. <puts on flameproof suit>
The first Eagle link should be a link to DesignSpark

stevech · Mar 28, 2014

nox771 said:
Hmm.. <puts on flameproof suit>
The first Eagle link should be a link to DesignSpark

Nah, DipTrace (free or cheap version). Great stuff. diptrace.com

stevech · Apr 3, 2014

How to restart (not reboot) Teensy 3.x, since the library to do that as in Teensy 2 doesn't exist yet.
see
post #21 on thread http://forum.pjrc.com/threads/24304...)-vs-_restart_Teensyduino()?p=45253#post45253

Pedvide · Apr 7, 2014

Teensy 3.x ADC library update, http://forum.pjrc.com/threads/25532-ADC-library-update-now-with-support-for-Teensy-3-1

pictographer · May 6, 2014

Oscilloscope advice:
http://forum.pjrc.com/threads/25730-Oscilloscope-advice?p=47209&viewfull=1#post47209

There's at east one other thread that has good scope advice. If I recall, it might talk about other cheap options and their limitations.

A related question is how to build an oscilloscope from a Teensy and why this is a fine learning exercise, but probably won't get a very useful tool without significant investment in additional parts and very challenging analog design.

pictographer · May 6, 2014

This forum software has its own FAQ, but it doesn't appear to be customized. Perhaps a link to this thread could be put there if not too much trouble.

pictographer · May 7, 2014

There's some really good stuff on reset in these and other threads but it's intermingled with lots of project debugging details:

http://forum.pjrc.com/threads/25306-Teensy-3-1-Reset?p=45344&viewfull=1#post45344
http://forum.pjrc.com/threads/25670-Update-Teensy-remotely-without-using-the-pushbutton
http://forum.pjrc.com/threads/24740-Will-pressing-the-reset-program-button-by-itself-erase-the-chip
http://forum.pjrc.com/threads/24304-_reboot_Teensyduino()-vs-_restart_Teensyduino()

Teensy Quick Reference: Code Examples, Tips and Tricks

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