CQ Publishing
トランジスタ技術2014年10月号第6章のソフトウェア
Information
tg_201410s6_Plethysmographs トランジスタ技術 2014年 10月号 第6章のソフトウェア
Program for Section 6 in October. 2014 issue of the Transistor Gijutsu
(Japanese electronics magazine)
概要
このプログラムは、
- 脈波データ取得（A-Dサンプリング、ハイパスフィルタ）
- 脈拍数の算出（パルス検出、LEDおよび同期音出力、移動平均処理）
を行うPulseRateクラスと、それらをUSBシリアル通信でホストへ送信するmain関数で構成されています。
PulseRate.h, PulseRate.cpp
- A-Dサンプリング - 100 SPS
- ハイパスフィルタ - 遮断周波数0.1Hz、1次バターワースフィルタ
- パルス検出 - 脈波を微分処理、5point移動平均して速度脈波を求め、
それを包絡線検波した波形を、速度脈波が再び超える点をパルス開始とする - LED、同期音出力 - パルス同期LED(10ms)、圧電サウンダ出力(1kHz、10ms)
- 移動平均処理 - 直近5拍分の平均値を脈波として算出
main.cpp
- PulseRateクラスのインスタンスを生成
- 処理開始メソッドを実行
- メインループ - ポーリングにより、脈波データ、脈拍数データの完了フラグが返されたら、
USBシリアル通信経由で、ホストへ送信する
シリアル通信フォーマット
- 4byte固定長パケット方式
- 脈波データパケット、脈拍数データパケットの２種類
| 脈波データパケット | 脈拍数データパケット | |
| 0x00 | パケットヘッダ（固定値0xAA） | パケットヘッダ（固定値0xAA） |
| 0x01 | 波形番号（0 - 99繰り返し） | 脈拍数ID（固定値0xBB） |
| 0x02, 0x03 | 脈波データ（singed, 2byte） | 脈拍数データ（20 - 300, 2byte） |
Description
This contains PulseRate class and main function.
PulseRate class:
- Acquiring pulse waveform (A-D sampling, high pass filter)
- Calculate pulse rate (Detecting pulse, Sync. LED and buzzer, moving averaging)
Main function:
- Send pulse waveform and rate to host via USB serial class.
PulseRate.h, PulseRate.cpp
- A-D sampling - 100 SPS
- High pass filter - Cut off frequency 0.1Hz, first order butterworth
- Detecting pulse - Calculating velocity pulse waveform by derivation and moving averaging (5point).
Moreover, calculating threshold waveform like envelope demodulator.
Detecting point the velocity waveform pass over the threshold waveform as starting pulse. - Sync. LED, buzzer - Synchronous pulse LED(10ms), piezo sounder(1kHz, 10ms)
- Moving averaging - Calculating pulse rate averaging the previous 5 pulse.
main.cpp
- Generating an instance of PulseRate class
- Executing start procedure method
- Main loop - sending pulse waveform data and pulse rate data via USB serial interface when detecting ready in return value.
Packet format for USB serial interface
- Packet size: 4 bytes(fixed)
- Two types of packets, pulse waveform packet and pulse rate packet
| Pulse waveform packet | Pulse rate packet | |
| 0x00 | Packet header (0xAA (fixed))） | Packet header (0xAA (fixed)) |
| 0x01 | Sampling number (0 - 99) | Pulse rate ID (0xBB (fixed)) |
| 0x02, 0x03 | Pulse waveform data (singed, 2byte) | Pulse rate data (20 - 300, 2byte) |
Revision 0:f0c12790aadb, committed 2014-09-11
- Comitter:
- t_tatsuoka
- Date:
- Thu Sep 11 15:02:45 2014 +0000
- Commit message:
- Name?tg_201410s6_Plethysmographs; Description?????????2014?10???6????????; Publish in :CQ Publishing
Changed in this revision
diff -r 000000000000 -r f0c12790aadb PulseRate.cpp
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/PulseRate.cpp Thu Sep 11 15:02:45 2014 +0000
@@ -0,0 +1,183 @@
+/**
+ * @file PulseRate.cpp
+ * @brief Calculate pulse waveform and pulse rate
+ * @date 2014.08.08
+ * @version 1.0.0
+ */
+ #include "PulseRate.h"
+
+/** Constructor
+ * @param sensor Pin for A/D converter
+ * @param sync_led Pin for synchronous LED
+ * @param beep Pin for piezo sounder
+ */
+ PulseRate::PulseRate(PinName sensor, PinName sync_led, PinName beep) :
+ _sensor(sensor), _sync_led(sync_led), _beep(beep) {
+
+ _sync_led = LED_OFF;
+ _val = 0;
+ _wave_flag = false;
+ _pr_flag = false;
+ _sampling_num = 0;
+ _mv_idx = 0;
+ _beep.period(1.0/BEEP_FREQ);
+}
+
+/** Start interval timer
+ */
+void PulseRate::start_sampling() {
+ _sampling.attach(this, &PulseRate::interval_timer, SAMPLING_RATE);
+}
+
+/** Get waveform data
+ * @param &num Sampling number
+ * @param &wave_val Waveform value
+ * @retval true Ready for data
+ * @retval false Not ready
+ */
+bool PulseRate::get_wave(uint32_t &num, int32_t &wave_val) {
+ if(_wave_flag) {
+ _wave_flag = false;
+ num = _sampling_num;
+ wave_val = _val;
+ return true;
+ } else {
+ return false;
+ }
+}
+
+/** Gat pulse rate
+ * @param &pr Pulse rate
+ * @retval true Ready for data
+ * @retval false Not ready
+ */
+ bool PulseRate::get_pr_val(uint32_t &pr) {
+ if(_pr_flag) {
+ _pr_flag = false;
+ pr = _pr;
+ return true;
+ } else {
+ return false;
+ }
+}
+
+/** Interval timer
+ */
+void PulseRate::interval_timer() {
+
+ /* Pulse waveform */
+ _val = ((int32_t)(_sensor.read_u16()) - AD_OFFSET); /* Get AD value */
+ _val = hpf(_val); /* High pass filter (Comment out if not necessary) */
+ _sampling_num = (_sampling_num + 1) % SPL_NUM; /* Update sampling number */
+ _wave_flag = true; /* Set ready flag for pulse waveform */
+
+ /* Pulse rate */
+ if(detect_peak(_val)) { /* If detecting pulse */
+ calc_pr(); /* Calculate pulse rate including flag set */
+ }
+
+ /* Control LED and Beep */
+ if(_pr_flag) {
+ _sync_led = LED_ON;
+ _beep.write(BEEP_LOUD);
+ } else {
+ _sync_led = LED_OFF;
+ _beep.write(0);
+ }
+}
+
+/** Fixed point high pass filter
+ * @param val Input value
+ * @return Output value
+ *
+ * A/D value of mbed is Q6 format.
+ * Please shift in advance if necessary.
+ */
+int32_t PulseRate::hpf(int32_t val) {
+ int32_t reg, ret_val;
+ int64_t temp_val;
+
+ temp_val = (int64_t)COEF_AH * (int64_t)_reg_hpf;
+ reg = val + (int32_t)(temp_val >> 30);
+ ret_val = reg - _reg_hpf;
+ temp_val = (int64_t)COEF_BH * (int64_t)ret_val;
+ ret_val = (int32_t)(temp_val >> 30);
+ _reg_hpf = reg;
+ return ret_val;
+}
+
+/** Detect pulse peak
+ * @param &val Waveform data value
+ * @retval true Detected pulse peak
+ * @retval false No detection
+ */
+bool PulseRate::detect_peak(int32_t val) {
+ int i;
+ bool retVal = false;
+
+ /* Calculate differential of input value */
+ _mv_buf[_mv_idx] = val - _prev_val;
+ _prev_val = val;
+ _mv_idx = (_mv_idx + 1) % MV_LENGTH;
+
+ /* Calculate moving averaging */
+ _detect_val = 0;
+ for(i=0; i<MV_LENGTH; i++)
+ {
+ _detect_val += _mv_buf[i];
+ }
+ _detect_val = _detect_val / MV_LENGTH;
+
+ /* Calculate exponential decline for threshold line */
+ _threshold_val = (int32_t)((double)_prev_th_val * TH_COEF);
+
+ if(_detect_val >= _threshold_val) {
+ /* If exceeding threshold */
+ if(_prev_dt_val < _prev_th_val){
+ /* If previous value is under threshold and over ignore value */
+ if((_detect_val > PEAK_MIN) && (_pr_counter >= PR_INT_MIN)) {
+ /* Detecting peak!!! */
+ retVal = true;
+ }
+ }
+ /* Previous threshold value is set to input value */
+ _prev_th_val = _detect_val;
+ } else {
+ /* Previous threshold value is set to decline value */
+ _prev_th_val = _threshold_val;
+ }
+ /* Update previous input value */
+ _prev_dt_val = _detect_val;
+
+ /* Increment pulse rate counter */
+ _pr_counter++;
+
+ return retVal;
+}
+
+/** Calculate pulse rate
+ */
+void PulseRate::calc_pr() {
+ int i;
+
+ /* If pulse rate counter is within maximum value */
+ if(_pr_counter <= PR_INT_MAX) {
+ /* Calculate moving averaging */
+ _pr_buf[_pr_idx] = _pr_counter;
+ _pr_idx = (_pr_idx + 1) % PR_LENGTH;
+ _pr = 0;
+ for(i=0; i<PR_LENGTH; i++)
+ {
+ _pr += _pr_buf[i];
+ }
+ /* Set pulse rate value */
+ _pr = PR_1MIN_SPL * PR_LENGTH / _pr;
+ } else {
+ /* Pulse rate is set to invalid value */
+ _pr = 0;
+ }
+ _pr_counter = 0;
+
+ /* Set pulse rate flag */
+ _pr_flag = true;
+}
diff -r 000000000000 -r f0c12790aadb PulseRate.h
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/PulseRate.h Thu Sep 11 15:02:45 2014 +0000
@@ -0,0 +1,87 @@
+/**
+ * @file PulseRate.h
+ * @brief Header file for PulseRate.cpp
+ * @date 2014.08.08
+ * @version 1.0.0
+ */
+#ifndef _INC_PulseRate
+#define _INC_PulseRate
+
+#include "mbed.h"
+
+#define LED_ON (0)
+#define LED_OFF (1)
+
+#define BEEP_FREQ (1000.0)
+#define BEEP_LOUD (0.5)
+
+#define SAMPLING_RATE (0.01) /* A/D sampling rate (10ms) */
+#define SPL_NUM (100) /* Range of sampling number (0 - 99) */
+
+#define AD_OFFSET (21845) /* Offset value for VREF (about +1.1V) */
+
+#define COEF_BH (0x3FCCB062) /* High pass filter b0, -b1 coefficient 0.1Hz/100Hz Q30 format */
+ /* Use (0x3F02946A) when 0.5Hz/100Hz Q30 format */
+#define COEF_AH (0x3F9960C5) /* High pass filter -a1 coefficient 0.1Hz/200Hz Q30 format */
+ /* Use (0x3E0528D5) when 0.5Hz/100Hz Q30 format */
+
+#define MV_LENGTH (5) /* Number of moving averaging for pulse detection */
+#define TH_COEF (0.993) /* Coefficient for pulse threshold (exponential decline) */
+#define PEAK_MIN (127) /* Ignore waveform as pulse under this value */
+
+#define PR_LENGTH (5) /* Number of average for pulse rate */
+#define PR_1MIN_SPL (6000) /* Number of sampling for 1 minute (60*100) */
+#define PR_INT_MAX (300) /* 20 bpm (60*100/20) */
+#define PR_INT_MIN (20) /* 300 bpm (60*100/300) */
+
+/** Calculate pulse waveform and pulse rate
+ */
+class PulseRate {
+
+public:
+ PulseRate(PinName sensor, PinName sync_led, PinName beep);
+ void start_sampling();
+ bool get_wave(uint32_t &num, int32_t &wave_val);
+ bool get_pr_val(uint32_t &pr);
+
+private:
+ Ticker _sampling; /* Interval timer for data sampling */
+
+ AnalogIn _sensor; /* A/D converter */
+ DigitalOut _sync_led; /* Synchronous LED */
+ PwmOut _beep; /* Piezo sounder */
+
+ /* Pulse waveform */
+ int32_t _val; /* Pulse waveform value */
+ int32_t _prev_val; /* Previous value */
+ int32_t _reg_hpf; /* High pass filter memory value */
+ bool _wave_flag; /* Pulse waveform set flag */
+
+ uint32_t _sampling_num; /* Sampling number */
+
+ /* Moving averaging */
+ int32_t _mv_buf[MV_LENGTH]; /* Circular buffer */
+ int32_t _mv_idx; /* Buffer index */
+
+ /* Threshold for detecting pulse */
+ int32_t _detect_val; /* Detection value */
+ int32_t _prev_dt_val; /* Previous data */
+
+ int32_t _threshold_val; /* Threshold value */
+ int32_t _prev_th_val; /* Previous data */
+
+ /* Pulse rate */
+ int32_t _pr_counter; /* Counter for pulse rate */
+ int32_t _pr_buf[PR_LENGTH]; /* Circular buffer */
+ int32_t _pr_idx; /* Buffer index */
+
+ int32_t _pr; /* Pulse rate value */
+ bool _pr_flag; /* Pulse rate set flag */
+
+ /* Member functions */
+ void interval_timer();
+ int32_t hpf(int32_t val);
+ bool detect_peak(int32_t val);
+ void calc_pr();
+};
+#endif /* INC_PulseRate */
diff -r 000000000000 -r f0c12790aadb USBDevice.lib --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/USBDevice.lib Thu Sep 11 15:02:45 2014 +0000 @@ -0,0 +1,1 @@ +http://mbed.org/users/mbed_official/code/USBDevice/#c09a0c9bf425
diff -r 000000000000 -r f0c12790aadb main.cpp
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Thu Sep 11 15:02:45 2014 +0000
@@ -0,0 +1,56 @@
+/**
+ * @file Main.cpp
+ * @brief Send pulse waveform and pulse rate
+ * @date 2014.08.08
+ * @version 1.0.0
+ */
+#include "mbed.h"
+#include "USBSerial.h"
+#include "PulseRate.h"
+
+#define PACKET_HEADER (0xAA)
+#define PULSE_RATE_ID (0xBB)
+#define BYTE_MASK (0xFF)
+
+USBSerial serial;
+PulseRate pr(p20, LED1, p26); /* AD, LED, Beep */
+
+/** Send data packet
+ * @param second_val Byte data at packet address 0x01
+ * @param data_val Short data at packet address 0x02, 0x03
+ */
+bool send_packet(int second_val, int data_val)
+{
+ if(serial.writeable()) {
+ serial.putc(PACKET_HEADER);
+ serial.putc(second_val & BYTE_MASK);
+ serial.putc((data_val >> 8 ) & BYTE_MASK);
+ serial.putc(data_val & BYTE_MASK);
+ return true;
+ }
+ else
+ {
+ return false;
+ }
+}
+
+/** Main function
+ */
+int main() {
+ uint32_t num;
+ int32_t wave;
+ uint32_t rate;
+
+ pr.start_sampling(); /* start procedure */
+
+ while(1) {
+ /* Pulse waveform */
+ if(pr.get_wave(num, wave)) {
+ send_packet(num, wave);
+ }
+ /* Pulse rate */
+ if(pr.get_pr_val(rate)) {
+ send_packet(PULSE_RATE_ID, rate);
+ }
+ }
+}
diff -r 000000000000 -r f0c12790aadb mbed.bld --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mbed.bld Thu Sep 11 15:02:45 2014 +0000 @@ -0,0 +1,1 @@ +http://mbed.org/users/mbed_official/code/mbed/builds/6213f644d804 \ No newline at end of file