原标题：Freescale Kinetis K5x系列脉搏血氧仪开发方案

　　freescale公司的Kinetis K5x系列MCU为设计人员提供包含集成运算的跨阻抗放大器和高分辨率模数转换器(ADC)和数模转换器(DAC)模块的模拟测量引擎.器件集成了高达512 KB闪存,提供IEEE®1588以太网和硬件加密,具有设备充电检测功能的全速USB 2.0 OTG以及一个灵活的低功率段式LCD控制器,主要用在医疗电子和工业应用.本文介绍了Kinetis K5x MCU系列主要特性,框图,以及MED-SPO2脉搏血氧仪开发套件框图,电路图和材料清单.

　　The Kinetis K5x MCU family is pin-, peripheral- and software-compatible with other Kinetis MCUs and provides designers with an analog measurement engine consisting of integrated operational and transimpedance amplifiers and high-resolution ADC and DAC modules.

　　The family also features IEEE® 1588 Ethernet and hardware encryption, full-speed USB 2.0 On-The-Go with device charger detect capability and a flexible low-power segment LCD controller with support for up to 320 segments. Devices start from 128 KB of flash in 64-pin LQFP packages extending up to 512 KB in a 144-pin MAPBGA package.

　　Kinetis K5x MCU系列主要特性:

　　• Operating Characteristics

　　– Voltage range: 1.71 to 3.6 V

　　– Flash write voltage range: 1.71 to 3.6 V

　　– Temperature range (ambient): -40 to 85℃

　　• Performance

　　– Up to 100 MHz ARM Cortex-M4 core with DSPinstructions delivering 1.25 Dhrystone MIPS perMHz

　　• Memories and memory interfaces

　　– Up to 512 KB program flash memory on non-FlexMemory devices

　　– Up to 256 KB program flash memory onFlexMemory devices

　　– Up to 256 KB FlexNVM on FlexMemory devices

　　– 4 KB FlexRAM on FlexMemory devices

　　– Up to 128 KB RAM

　　– Serial programming interface (EzPort)

　　– FlexBus external bus interface

　　• Clocks

　　– 3 to 32 MHz crystal oscillator

　　– 32 kHz crystal oscillator

　　– Multi-purpose clock generator

　　• System peripherals

　　– Multiple low-power modes to provide poweroptimization based on application requirements

　　– Memory protection unit with multi-masterprotection

　　– 16-channel DMA controller, supporting up to 63request sources

　　– External watchdog monitor

　　– Software watchdog

　　– Low-leakage wakeup unit

　　• Security and integrity modules

　　– Hardware CRC module to support fast cyclicredundancy checks

　　– Hardware random-number generator

　　– Hardware encryption supporting DES, 3DES, AES,MD5, SHA-1, and SHA-256 algorithms

　　– 128-bit unique identification (ID) number per chip

　　• Human-machine interface

　　– Segment LCD controller supporting up to 40frontplanes and 8 backplanes, or 44 frontplanes and4 backplanes, depending on the package size

　　– Low-power hardware touch sensor interface (TSI)

　　– General-purpose input/output

　　• Analog modules

　　– Two 16-bit SAR ADCs

　　– Programmable gain amplifier (PGA) (up to x64)integrated into each ADC

　　– Two 12-bit DACs

　　– Two operational amplifiers

　　– Two transimpedance amplifiers

　　– Three analog comparators (CMP) containing a 6-bitDAC and programmable reference input

　　– Voltage reference

　　• Timers

　　– Programmable delay block

　　– Eight-channel motor control/general purpose/PWMtimer

　　– Two 2-channel quadrature decoder/general purposetimers

　　– IEEE 1588 timers

　　– Periodic interrupt timers

　　– 16-bit low-power timer

　　– Carrier modulator transmitter

　　– Real-time clock

　　Communication interfaces

　　– Ethernet controller with MII and RMII interface to external PHY and hardware IEEE 1588 capability

　　– USB full-/low-speed On-the-Go controller with on-chip transceiver

　　– Three SPI modules

　　– Two I2C modules

　　– Six UART modules

　　– Secure Digital host controller (SDHC)

　　– I2S module

　　图1.Kinetis K5x MCU系列框图

　　脉搏血氧测量是监测血液中含氧血红蛋白百分比的一种简单的非侵入式方法。脉搏血氧仪间接地测量患者血液的氧饱和度及皮肤中血液量的变化。LCD显示屏上会显示血氧饱和度及心率。

　　脉搏血氧仪可以作为独立的便携式装置出售，也可以连接到更大型的病患监护系统。

　　飞思卡尔提供具有LCD显示屏驱动功能的超低功率MCU。此类器件是便携式脉搏血氧仪的理想选择。

　　Pulse oximetry is the non-invasive measurement of the oxygen saturation (SpO2). Oxygen saturation is defined as themeasurement of the amount of oxygen dissolved in blood, based on the detection of Hemoglobin and Deoxyhemoglobin.

　　Two different light wavelengths are used to measure the actual difference in the absorption spectra of HbO2 and Hb. Thebloodstream is affected by the concentration of HbO2 and Hb, and their absorption coefficients are measured using twowavelengths 660 nm (red light spectra) and 940 nm (infrared light spectra). Deoxygenated and oxygenated hemoglobinabsorb different wavelengths. Deoxygenated hemoglobin (Hb) has a higher absorption at 660 nm and oxygenatedhemoglobin (HbO2) has a higher absorption at 940 nm.

　　The pulse oximeter is implemented using the Freescale MCU Kinetis K53 which embeds the following key features for thepulse oximetry signal treatment, among other medical oriented applications:

　　• 32-bit ARM? Cortex™-M4 core up to 100 MHz, bus speed up to 50 MHz

　　• DSP instructions for signal filtering

　　• Two Operational Amplifiers (OpAmp)

　　• Two Transimpedance Amplifiers (TRIAMP)

　　• USB connectivity as host, device or On-The-Go (OTG)

　　• Up to four pairs of differential and 24 single-ended 16-bit ADC channels

　　• 3 x 16-bit Flex Timer Modules (FTM) with PWM capability

　　图2.MED-SPO2脉搏血氧仪开发套件外形图

　　图3.MED-SPO2脉搏血氧仪功能框图