Even if you don’t want to use the Arduino IDE for building your application, or want to do fancy things that only the evil, convoluted syntax of Makefiles can provide, you can do Teensy development on the Mac from the command line. While there are a lot of guides out there on how to do it, I hadn’t seen a complete step-by-step set of instructions.

So with no further ado, here are the steps for building Teensy applications on Mac OS using the Makefiles and the mighty command line.

1. Download the Arduino IDE from https://www.arduino.cc/en/main/software and install it.
2. Download Teensyduino from https://www.pjrc.com/teensy/td_download.html and install it.
3. Download a “basic project template” for Teensy. The original is at https://github.com/apmorton/teensy-template but I’ve been using the fork at https://github.com/a-j-f/teensy-template which has been updated more recently and uses the Teensy CLI Loader for uploading to the device.
4. Update the Makefile to set your Teensy model
5. Type make to build, or make upload to install on your Teensy

If you’re wanting to monitor the serial console of your Teensy over USB, install a terminal program like CoolTerm. Alternatively, if you use Homebrew or MacPorts you can use a console-based terminal program like minicom. Once the USB connector is plugged in, your Teensy will show up as something like /dev/cu.usbmodem45504901. The communications settings will be 115200 baud, 8 bit, no parity, 1 stop bit.

Cambot is a project based on the Teensy development board. Cambot creates an infra-red “trip beam” that triggers a pre-focused Nikon D90.

To create an IR beam and detector that work in direct sunlight, Cambot pulses the IR source every 10ms, and compares detected signal between the on and off states. If it’s greater than a threshold, it’s considered a valid signal. The sensor also has a vary small aperture which is additionally shielded with a filter to reduce the ambient IR. When powered on, Cambot goes into calibration mode, which lights up an LED when it detects a good signal. This is critical for lining up the IR sources and detector — once a good signal is sustained for 3 seconds, Cambot goes into “armed” mode. When armed, breaking the beam will turn off the IR source, half-press the camera’s shutter for 10ms so the camera can compute exposure, and then fires off a burst of pictures before re-arming itself.

While there’s nothing in Cambot that couldn’t have been implemented with, say, 555 timers, counters, and gates, having the ability to drive digital logic with C code makes things much more flexible. When trying to determine the proper threshold values for arming and triggering, the ability to output hex data over the USB connector to a host computer was invaluable.

Here’s Cambot’s first run, when the trip-beam was positioned over a tempting milkweed blossom in the back yard.

If there’s any interest, I’ll post a circuit diagram and source code.