In the last few weeks we’ve been working diligently on getting the photosynq handheld device actually handheld. Until now we had taken data using the standard Ideaspec hardware but with the new LEDs, detectors, and light guide setup. Now it’s time to shed the Ideaspec hardware totally and go completely cordless.
We’re almost there.
Robert is in the process of creating a shield (to use arduino-ish terminology) for the Teensy 3.0. This shield does a lot of important stuff – it contains an SD card reader, provides AC filtering of the detector signal, creates a high quality / low noise analog reference signal for the ADC, and includes full brightness control over all of the LEDs. It’s a work in progress, but we hope to have an early version in a few weeks before he goes on vacation of Croatia for the summer, where nice beaches and family time will probably out-compete time spent on this project 🙂
I’ve been writing the Arduino code to run a basic fluorescence measurement – and it’s pretty much done. It interfaces through the serial port and has a simple program for user input before sampling (“do you want to create a new file y/n?” and “would you like to run a calibration?”… etc). It also saves the data on an SD card, which will make sending the data to a cell phone a piece of cake later. I’m working on getting the code on github, but for now I’m just posting to the Teensy forum at PJRC (Teensy is the arduino-based microcontroller that we’re using) located here.
Though the code itself works like a champ, the signal quality is not quite as good as when we use the Ideaspec signal processing hardware. It looks like we’ve got a lot of noise as you can see in the graphs below (the left is Ideaspec, the right is the handheld). But we’re pretty sure we understand the source of the noise and Robert’s on it – you can read about the source of the noise here, and expect to see more posts on PJRC from Robert which describes how we’re dealing with it.
The last big “cords” left to get rid of is the main power and the 12V power which is pushed through the detector. Once those are gone, we’ll be truly cordless… I can’t wait!