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) |
PulseRate.cpp@0:f0c12790aadb, 2014-09-11 (annotated)
- Committer:
- t_tatsuoka
- Date:
- Thu Sep 11 15:02:45 2014 +0000
- Revision:
- 0:f0c12790aadb
Name?tg_201410s6_Plethysmographs; Description?????????2014?10???6????????; Publish in :CQ Publishing
Who changed what in which revision?
User | Revision | Line number | New contents of line |
---|---|---|---|
t_tatsuoka | 0:f0c12790aadb | 1 | /** |
t_tatsuoka | 0:f0c12790aadb | 2 | * @file PulseRate.cpp |
t_tatsuoka | 0:f0c12790aadb | 3 | * @brief Calculate pulse waveform and pulse rate |
t_tatsuoka | 0:f0c12790aadb | 4 | * @date 2014.08.08 |
t_tatsuoka | 0:f0c12790aadb | 5 | * @version 1.0.0 |
t_tatsuoka | 0:f0c12790aadb | 6 | */ |
t_tatsuoka | 0:f0c12790aadb | 7 | #include "PulseRate.h" |
t_tatsuoka | 0:f0c12790aadb | 8 | |
t_tatsuoka | 0:f0c12790aadb | 9 | /** Constructor |
t_tatsuoka | 0:f0c12790aadb | 10 | * @param sensor Pin for A/D converter |
t_tatsuoka | 0:f0c12790aadb | 11 | * @param sync_led Pin for synchronous LED |
t_tatsuoka | 0:f0c12790aadb | 12 | * @param beep Pin for piezo sounder |
t_tatsuoka | 0:f0c12790aadb | 13 | */ |
t_tatsuoka | 0:f0c12790aadb | 14 | PulseRate::PulseRate(PinName sensor, PinName sync_led, PinName beep) : |
t_tatsuoka | 0:f0c12790aadb | 15 | _sensor(sensor), _sync_led(sync_led), _beep(beep) { |
t_tatsuoka | 0:f0c12790aadb | 16 | |
t_tatsuoka | 0:f0c12790aadb | 17 | _sync_led = LED_OFF; |
t_tatsuoka | 0:f0c12790aadb | 18 | _val = 0; |
t_tatsuoka | 0:f0c12790aadb | 19 | _wave_flag = false; |
t_tatsuoka | 0:f0c12790aadb | 20 | _pr_flag = false; |
t_tatsuoka | 0:f0c12790aadb | 21 | _sampling_num = 0; |
t_tatsuoka | 0:f0c12790aadb | 22 | _mv_idx = 0; |
t_tatsuoka | 0:f0c12790aadb | 23 | _beep.period(1.0/BEEP_FREQ); |
t_tatsuoka | 0:f0c12790aadb | 24 | } |
t_tatsuoka | 0:f0c12790aadb | 25 | |
t_tatsuoka | 0:f0c12790aadb | 26 | /** Start interval timer |
t_tatsuoka | 0:f0c12790aadb | 27 | */ |
t_tatsuoka | 0:f0c12790aadb | 28 | void PulseRate::start_sampling() { |
t_tatsuoka | 0:f0c12790aadb | 29 | _sampling.attach(this, &PulseRate::interval_timer, SAMPLING_RATE); |
t_tatsuoka | 0:f0c12790aadb | 30 | } |
t_tatsuoka | 0:f0c12790aadb | 31 | |
t_tatsuoka | 0:f0c12790aadb | 32 | /** Get waveform data |
t_tatsuoka | 0:f0c12790aadb | 33 | * @param &num Sampling number |
t_tatsuoka | 0:f0c12790aadb | 34 | * @param &wave_val Waveform value |
t_tatsuoka | 0:f0c12790aadb | 35 | * @retval true Ready for data |
t_tatsuoka | 0:f0c12790aadb | 36 | * @retval false Not ready |
t_tatsuoka | 0:f0c12790aadb | 37 | */ |
t_tatsuoka | 0:f0c12790aadb | 38 | bool PulseRate::get_wave(uint32_t &num, int32_t &wave_val) { |
t_tatsuoka | 0:f0c12790aadb | 39 | if(_wave_flag) { |
t_tatsuoka | 0:f0c12790aadb | 40 | _wave_flag = false; |
t_tatsuoka | 0:f0c12790aadb | 41 | num = _sampling_num; |
t_tatsuoka | 0:f0c12790aadb | 42 | wave_val = _val; |
t_tatsuoka | 0:f0c12790aadb | 43 | return true; |
t_tatsuoka | 0:f0c12790aadb | 44 | } else { |
t_tatsuoka | 0:f0c12790aadb | 45 | return false; |
t_tatsuoka | 0:f0c12790aadb | 46 | } |
t_tatsuoka | 0:f0c12790aadb | 47 | } |
t_tatsuoka | 0:f0c12790aadb | 48 | |
t_tatsuoka | 0:f0c12790aadb | 49 | /** Gat pulse rate |
t_tatsuoka | 0:f0c12790aadb | 50 | * @param &pr Pulse rate |
t_tatsuoka | 0:f0c12790aadb | 51 | * @retval true Ready for data |
t_tatsuoka | 0:f0c12790aadb | 52 | * @retval false Not ready |
t_tatsuoka | 0:f0c12790aadb | 53 | */ |
t_tatsuoka | 0:f0c12790aadb | 54 | bool PulseRate::get_pr_val(uint32_t &pr) { |
t_tatsuoka | 0:f0c12790aadb | 55 | if(_pr_flag) { |
t_tatsuoka | 0:f0c12790aadb | 56 | _pr_flag = false; |
t_tatsuoka | 0:f0c12790aadb | 57 | pr = _pr; |
t_tatsuoka | 0:f0c12790aadb | 58 | return true; |
t_tatsuoka | 0:f0c12790aadb | 59 | } else { |
t_tatsuoka | 0:f0c12790aadb | 60 | return false; |
t_tatsuoka | 0:f0c12790aadb | 61 | } |
t_tatsuoka | 0:f0c12790aadb | 62 | } |
t_tatsuoka | 0:f0c12790aadb | 63 | |
t_tatsuoka | 0:f0c12790aadb | 64 | /** Interval timer |
t_tatsuoka | 0:f0c12790aadb | 65 | */ |
t_tatsuoka | 0:f0c12790aadb | 66 | void PulseRate::interval_timer() { |
t_tatsuoka | 0:f0c12790aadb | 67 | |
t_tatsuoka | 0:f0c12790aadb | 68 | /* Pulse waveform */ |
t_tatsuoka | 0:f0c12790aadb | 69 | _val = ((int32_t)(_sensor.read_u16()) - AD_OFFSET); /* Get AD value */ |
t_tatsuoka | 0:f0c12790aadb | 70 | _val = hpf(_val); /* High pass filter (Comment out if not necessary) */ |
t_tatsuoka | 0:f0c12790aadb | 71 | _sampling_num = (_sampling_num + 1) % SPL_NUM; /* Update sampling number */ |
t_tatsuoka | 0:f0c12790aadb | 72 | _wave_flag = true; /* Set ready flag for pulse waveform */ |
t_tatsuoka | 0:f0c12790aadb | 73 | |
t_tatsuoka | 0:f0c12790aadb | 74 | /* Pulse rate */ |
t_tatsuoka | 0:f0c12790aadb | 75 | if(detect_peak(_val)) { /* If detecting pulse */ |
t_tatsuoka | 0:f0c12790aadb | 76 | calc_pr(); /* Calculate pulse rate including flag set */ |
t_tatsuoka | 0:f0c12790aadb | 77 | } |
t_tatsuoka | 0:f0c12790aadb | 78 | |
t_tatsuoka | 0:f0c12790aadb | 79 | /* Control LED and Beep */ |
t_tatsuoka | 0:f0c12790aadb | 80 | if(_pr_flag) { |
t_tatsuoka | 0:f0c12790aadb | 81 | _sync_led = LED_ON; |
t_tatsuoka | 0:f0c12790aadb | 82 | _beep.write(BEEP_LOUD); |
t_tatsuoka | 0:f0c12790aadb | 83 | } else { |
t_tatsuoka | 0:f0c12790aadb | 84 | _sync_led = LED_OFF; |
t_tatsuoka | 0:f0c12790aadb | 85 | _beep.write(0); |
t_tatsuoka | 0:f0c12790aadb | 86 | } |
t_tatsuoka | 0:f0c12790aadb | 87 | } |
t_tatsuoka | 0:f0c12790aadb | 88 | |
t_tatsuoka | 0:f0c12790aadb | 89 | /** Fixed point high pass filter |
t_tatsuoka | 0:f0c12790aadb | 90 | * @param val Input value |
t_tatsuoka | 0:f0c12790aadb | 91 | * @return Output value |
t_tatsuoka | 0:f0c12790aadb | 92 | * |
t_tatsuoka | 0:f0c12790aadb | 93 | * A/D value of mbed is Q6 format. |
t_tatsuoka | 0:f0c12790aadb | 94 | * Please shift in advance if necessary. |
t_tatsuoka | 0:f0c12790aadb | 95 | */ |
t_tatsuoka | 0:f0c12790aadb | 96 | int32_t PulseRate::hpf(int32_t val) { |
t_tatsuoka | 0:f0c12790aadb | 97 | int32_t reg, ret_val; |
t_tatsuoka | 0:f0c12790aadb | 98 | int64_t temp_val; |
t_tatsuoka | 0:f0c12790aadb | 99 | |
t_tatsuoka | 0:f0c12790aadb | 100 | temp_val = (int64_t)COEF_AH * (int64_t)_reg_hpf; |
t_tatsuoka | 0:f0c12790aadb | 101 | reg = val + (int32_t)(temp_val >> 30); |
t_tatsuoka | 0:f0c12790aadb | 102 | ret_val = reg - _reg_hpf; |
t_tatsuoka | 0:f0c12790aadb | 103 | temp_val = (int64_t)COEF_BH * (int64_t)ret_val; |
t_tatsuoka | 0:f0c12790aadb | 104 | ret_val = (int32_t)(temp_val >> 30); |
t_tatsuoka | 0:f0c12790aadb | 105 | _reg_hpf = reg; |
t_tatsuoka | 0:f0c12790aadb | 106 | return ret_val; |
t_tatsuoka | 0:f0c12790aadb | 107 | } |
t_tatsuoka | 0:f0c12790aadb | 108 | |
t_tatsuoka | 0:f0c12790aadb | 109 | /** Detect pulse peak |
t_tatsuoka | 0:f0c12790aadb | 110 | * @param &val Waveform data value |
t_tatsuoka | 0:f0c12790aadb | 111 | * @retval true Detected pulse peak |
t_tatsuoka | 0:f0c12790aadb | 112 | * @retval false No detection |
t_tatsuoka | 0:f0c12790aadb | 113 | */ |
t_tatsuoka | 0:f0c12790aadb | 114 | bool PulseRate::detect_peak(int32_t val) { |
t_tatsuoka | 0:f0c12790aadb | 115 | int i; |
t_tatsuoka | 0:f0c12790aadb | 116 | bool retVal = false; |
t_tatsuoka | 0:f0c12790aadb | 117 | |
t_tatsuoka | 0:f0c12790aadb | 118 | /* Calculate differential of input value */ |
t_tatsuoka | 0:f0c12790aadb | 119 | _mv_buf[_mv_idx] = val - _prev_val; |
t_tatsuoka | 0:f0c12790aadb | 120 | _prev_val = val; |
t_tatsuoka | 0:f0c12790aadb | 121 | _mv_idx = (_mv_idx + 1) % MV_LENGTH; |
t_tatsuoka | 0:f0c12790aadb | 122 | |
t_tatsuoka | 0:f0c12790aadb | 123 | /* Calculate moving averaging */ |
t_tatsuoka | 0:f0c12790aadb | 124 | _detect_val = 0; |
t_tatsuoka | 0:f0c12790aadb | 125 | for(i=0; i<MV_LENGTH; i++) |
t_tatsuoka | 0:f0c12790aadb | 126 | { |
t_tatsuoka | 0:f0c12790aadb | 127 | _detect_val += _mv_buf[i]; |
t_tatsuoka | 0:f0c12790aadb | 128 | } |
t_tatsuoka | 0:f0c12790aadb | 129 | _detect_val = _detect_val / MV_LENGTH; |
t_tatsuoka | 0:f0c12790aadb | 130 | |
t_tatsuoka | 0:f0c12790aadb | 131 | /* Calculate exponential decline for threshold line */ |
t_tatsuoka | 0:f0c12790aadb | 132 | _threshold_val = (int32_t)((double)_prev_th_val * TH_COEF); |
t_tatsuoka | 0:f0c12790aadb | 133 | |
t_tatsuoka | 0:f0c12790aadb | 134 | if(_detect_val >= _threshold_val) { |
t_tatsuoka | 0:f0c12790aadb | 135 | /* If exceeding threshold */ |
t_tatsuoka | 0:f0c12790aadb | 136 | if(_prev_dt_val < _prev_th_val){ |
t_tatsuoka | 0:f0c12790aadb | 137 | /* If previous value is under threshold and over ignore value */ |
t_tatsuoka | 0:f0c12790aadb | 138 | if((_detect_val > PEAK_MIN) && (_pr_counter >= PR_INT_MIN)) { |
t_tatsuoka | 0:f0c12790aadb | 139 | /* Detecting peak!!! */ |
t_tatsuoka | 0:f0c12790aadb | 140 | retVal = true; |
t_tatsuoka | 0:f0c12790aadb | 141 | } |
t_tatsuoka | 0:f0c12790aadb | 142 | } |
t_tatsuoka | 0:f0c12790aadb | 143 | /* Previous threshold value is set to input value */ |
t_tatsuoka | 0:f0c12790aadb | 144 | _prev_th_val = _detect_val; |
t_tatsuoka | 0:f0c12790aadb | 145 | } else { |
t_tatsuoka | 0:f0c12790aadb | 146 | /* Previous threshold value is set to decline value */ |
t_tatsuoka | 0:f0c12790aadb | 147 | _prev_th_val = _threshold_val; |
t_tatsuoka | 0:f0c12790aadb | 148 | } |
t_tatsuoka | 0:f0c12790aadb | 149 | /* Update previous input value */ |
t_tatsuoka | 0:f0c12790aadb | 150 | _prev_dt_val = _detect_val; |
t_tatsuoka | 0:f0c12790aadb | 151 | |
t_tatsuoka | 0:f0c12790aadb | 152 | /* Increment pulse rate counter */ |
t_tatsuoka | 0:f0c12790aadb | 153 | _pr_counter++; |
t_tatsuoka | 0:f0c12790aadb | 154 | |
t_tatsuoka | 0:f0c12790aadb | 155 | return retVal; |
t_tatsuoka | 0:f0c12790aadb | 156 | } |
t_tatsuoka | 0:f0c12790aadb | 157 | |
t_tatsuoka | 0:f0c12790aadb | 158 | /** Calculate pulse rate |
t_tatsuoka | 0:f0c12790aadb | 159 | */ |
t_tatsuoka | 0:f0c12790aadb | 160 | void PulseRate::calc_pr() { |
t_tatsuoka | 0:f0c12790aadb | 161 | int i; |
t_tatsuoka | 0:f0c12790aadb | 162 | |
t_tatsuoka | 0:f0c12790aadb | 163 | /* If pulse rate counter is within maximum value */ |
t_tatsuoka | 0:f0c12790aadb | 164 | if(_pr_counter <= PR_INT_MAX) { |
t_tatsuoka | 0:f0c12790aadb | 165 | /* Calculate moving averaging */ |
t_tatsuoka | 0:f0c12790aadb | 166 | _pr_buf[_pr_idx] = _pr_counter; |
t_tatsuoka | 0:f0c12790aadb | 167 | _pr_idx = (_pr_idx + 1) % PR_LENGTH; |
t_tatsuoka | 0:f0c12790aadb | 168 | _pr = 0; |
t_tatsuoka | 0:f0c12790aadb | 169 | for(i=0; i<PR_LENGTH; i++) |
t_tatsuoka | 0:f0c12790aadb | 170 | { |
t_tatsuoka | 0:f0c12790aadb | 171 | _pr += _pr_buf[i]; |
t_tatsuoka | 0:f0c12790aadb | 172 | } |
t_tatsuoka | 0:f0c12790aadb | 173 | /* Set pulse rate value */ |
t_tatsuoka | 0:f0c12790aadb | 174 | _pr = PR_1MIN_SPL * PR_LENGTH / _pr; |
t_tatsuoka | 0:f0c12790aadb | 175 | } else { |
t_tatsuoka | 0:f0c12790aadb | 176 | /* Pulse rate is set to invalid value */ |
t_tatsuoka | 0:f0c12790aadb | 177 | _pr = 0; |
t_tatsuoka | 0:f0c12790aadb | 178 | } |
t_tatsuoka | 0:f0c12790aadb | 179 | _pr_counter = 0; |
t_tatsuoka | 0:f0c12790aadb | 180 | |
t_tatsuoka | 0:f0c12790aadb | 181 | /* Set pulse rate flag */ |
t_tatsuoka | 0:f0c12790aadb | 182 | _pr_flag = true; |
t_tatsuoka | 0:f0c12790aadb | 183 | } |