Pulse Oximeter Reference Design

The design with 8-bit MCUs supports communication interfaces, an ECG sensor, and a modular system for making and testing medical applications.

Pulse oximetry is a non-invasive method for measuring blood oxygen saturation (SpO2). It determines the amount of oxygen dissolved in blood by detecting haemoglobin (Hb) and deoxyhemoglobin (HbO2). The MED-SPO2 Tower System module reference design from NXP Semiconductors is a medical-focused development tool for the 9S08MM Flexis 8-bit, MCF51MM ColdFire 32-bit, and Kinetis 32-bit MCU families. It supports pulse oximetry application development and is compatible with TWR-K53N512, TWR-MCF51MM, and TWR-S08MM128 Tower System modules.

The measurement relies on two light wavelengths—660 nm (red) and 940 nm (infrared)—to analyze differences in absorption. Deoxygenated haemoglobin (Hb) absorbs more light at 660 nm, while oxygenated haemoglobin (HbO2) absorbs more at 940 nm. These absorption differences help assess oxygen levels in the bloodstream.

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The 9S08MM128/64/32 is an 8-bit microcontroller that combines USB connectivity, graphic display support, and high measurement accuracy, enabling cost-effective product development with enhanced features. It is well-suited for medical devices and applications requiring precise analogue performance, such as instrumentation and industrial control. It is part of the Flexis microcontroller series.

The MCF51MM256/128 is a 32-bit microcontroller (MCU) that offers ultra-low power operation, USB connectivity, graphic display support, and high measurement accuracy. It enables cost-effective development of feature-rich products. Designed for medical applications and precision analogue tasks in instrumentation and industrial control, it is part of the Flexis MCU series.

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The TWR-K53N512 is a development tool for the NXP K53 Kinetis MCU family. As part of the Tower System, a modular development platform, it accelerates product development with packaged evaluation boards, tools, and runtime software. The MCU module can function as a standalone debug tool and is available separately. It also interfaces with the medical expansion connector and TWRPI-SLCD modules.

The TWR-MCF51MM module is a development board for the NXP MCF51MM256 Flexis ColdFire 32-bit MCUs, designed for evaluating and prototyping medical applications. It includes an electrocardiograph sensor as part of the evaluation system and functions as a standalone debug tool or as part of the modular Tower System development platform.

The TWR-S08MM128 is an NXP 9S08MM128 Flexis 8-bit MCU development tool designed for evaluating and prototyping medical applications. It supports external communication interfaces, features an open connector for a MED-EKG development board, and includes an electrocardiograph sensor as part of the evaluation system. It functions as a standalone debug tool or as part of the modular Tower System development platform.

NXP has tested this reference design. It comes with a bill of materials (BOM), schematics, and more. The company’s website has additional data about the reference design. To read more about this reference design, click here.