An open-source platform for the development of microcontroller based multi-wavelength oximetry

Abstract

We present here, an open-source printed circuit board (PCB) platform for the prototyping, testing and trialing of non-invasive oximeter devices. The system is designed around a dspic33fj128gp804 microcontroller with coding in C. It can control over 100 LED and photodiode devices and has two modes, one for calibration and one for signal interrogation. At the top-level, the microcontroller has ports dedicated for LED and photodiode control, with EEPROM and SD card for storage, alphanumeric display for menu control and graphical display showing relevant waveforms. Further the device is battery powered and rechargeable. This device was designed with consideration to robustness, power-efficient operation, expandable hardware and algorithms and cheap off the shelf components, ensuring it can be used and repaired in low-resource settings. We show a working example device calculating total Haemoglobin, which has relevance World-Wide as a non-invasive anaemia detector. Continuous operation the device consumes approx. 222 mW. Under these circumstances four AA batteries (2650 mAh) could operate for over eight hours allowing general use operation of several weeks, without charging.