ECG Simulator 2. Steps                                     ECG SIMULATOR  Purpose simulate the normal sinus rhythm ECG signal 3 leads RA,LA,RL  Background   In normal electrocardiography ECG or EKG if youre German, three leads make up the  Einthovens triangle. Two leads are taped to the right and left side of the chest above  the heart RA right arm, LA left arm and one lead is taped to the lower chest, typically  on the right hip RL right leg. Its important to know that these ECG signals are millivolts in amplitude. This can be achieved by           feeding the DA converter through a voltage divider to get to the millivolt levels. The ECG signal   I found a suitable ECG waveform from the internet. Here is how I converted a picture from my  monitor screen to a C language array of AD values, each spaced 1. A. Screen shot of waveform using the free screen capture program MWSNAP                         http www. B. Digitize the jpeg waveform using the free digitizing program ENGAUGE                http digitizer. Serial Ecg Frequency' title='Serial Ecg Frequency' />C I wrote a Python program to convert the rather irregular samples from ENGAUGE          to an array of values spaced 1. Then I created a text file where these data points were part of a C language array          construct that is, the data points are C initializers. D Cut and paste from the text file the C data array with initializers into the          Arduino sketch below. Arduino Resources      Digital Output 9  chip select the 7 segment display SPI port low to select    Digital Output 1. DA converter  low to select    Digital Output 1. SDI data to the DA converter  SPI interface    Digital Output 1. SCK clock to the DA converter SPI interface     Analog Input   0  center wiper pin of 5k ohm pot heart rate adjust    I followed the Timer. Sebastian Wallin    http popdevelop. I set up the SPI interface according to the excellent instructions of Australian John Boxall,    whose wonderful website has many excellent Arduino tutorials     http tronixstuff. Programmer  James P Lynch                             lynch. BBjpegwm-1024x408.jpg' alt='Serial Ecg Frequency' title='Serial Ecg Frequency' />SPI. SPI interface to the DA converter and 7 segment displayinclude lt Wire. Wire library various constants used by the waveform generatordefine INIT          0define IDLE        1define QRS         2define FOUR      4define THREE    3define TWO         2define ONE         1    ydata5. Waveform is scaled for a 1. DA converter 0. A 6. ECG would require this waveform 5. Num. Samples sizeofydata 2               number of elements in ydata aboveunsigned int  QRSCount 0                                                 running QRS period msec countunsigned int  Idle. EE Times connects the global electronics community through news, analysis, education, and peertopeer discussion around technology, business, products and design. Search and browse Intel processors and chipsets by platform code name, brand name, application, or release date. DSC6000. The new DSC6000 family is the industrys smallest MEMS MHz oscillator with the lowest power consumption over full frequency range of 2 KHz to 100 MHz. Count 0                                                   running Idle period msec countunsigned long Idle. Game Maker 8 Pinball Tutorial. Period 0                                               idle period is adjusted by pot to set heart rateunsigned int  State INIT                                                     states are INIT, QRS, and IDLEunsigned int  Display. Count 0                                           counts 5. Timer. 2 reload value, globally availablefloat         Beats. Per. Minute                                                     floating point representation of the heart rateunsigned int  Bpm                                                                 integer version of heart rate times 1. Bpm. Low                                                           lowest heart rate allowed x. Bpm. High                                                         highest heart rate allowed x. Value                                                                         place holder for analog input 0unsigned long Bpm. Values3. 2 0, 0, 0, 0, 0, 0, 0, 0,     holds 3. Bpm. Average 0                                           used in a simple averaging filterunsigned char Index 0                                                       used in a simple averaging filter unsigned int  Display. Value 0                                           filtered Beats Per Minute sent to displayvoid setup   Configure the output ports 1 msec intrerrupt indicator and DA SPI supportpin. Mode9, OUTPUT                     7 segment display chip select   low to select chippin. Mode1. 0, OUTPUT                    DA converter chip select       low to select chippin. Mode1. 1, OUTPUT                    SDI datapin. TOMB050109Cwm21-1024x417.jpg' alt='Serial Ecg Frequency' title='Serial Ecg Frequency' />Mode1. OUTPUT                    SCK clock  initial state of SPI interface. SPI. begin                                                           wake up the SPI bus. SPI. set. Data. Mode0                                           mode CPHA0, data captured on clocks rising edge low to highSPI. Clock. DividerSPICLOCKDIV6. SPI. set. Bit. OrderMSBFIRST                             bit 7 clocks out first establish the heart rate range allowed Bpm. Low  3. 00 3. 0 bpm x 1. Bpm. High 6. 0. Num. Samples 0. Bpm. Low 3. Bpm. High 6. 0. 0 floatNum. Samples 0. 0. 01 1. First disable the timer overflow interrupt while were configuring. Serial Ecg Frequency' title='Serial Ecg Frequency' />TIMSK2 1lt lt TOIE2  Configure timer. PWM etc. TCCR2. A 1lt lt WGM2. WGM2. 0 TCCR2. B 1lt lt WGM2. Select clock source internal IO clock  ASSR 1lt lt AS2  Disable Compare Match A interrupt enable only want overflow  TIMSK2 1lt lt OCIE2. A  Now configure the prescaler to CPU clock divided by 1. TCCR2. B 1lt lt CS2. CS2. 0 Set bits. TCCR2. B 1lt lt CS2. Clear bit  We need to calculate a proper value to load the timer counter. The following loads the value 1. Timer 2 counter register The math behind this is CPU frequency prescaler value 1. Hz 8us. desired period 8us 1. MAXuint. 8 1 1. Save value globally for later reload in ISR  tcnt. Finally load end enable the timer  TCNT2 tcnt. TIMSK2 1lt lt TOIE2 void loop   read from the heart rate pot Analog Input 0 Value analog. Read0  map the Analog Input 0 range 0. Bpm range 3. 00. Bpm mapValue, 0, 1. Bpm. Low, Bpm. High  To lessen the jitter or bounce in the displays least significant digit, a moving average filter 3. Bpm. ValuesIndex Bpm                       add latest sample to eight element arrayif Index 3. Index 0 Bpm. Average 0 for int  i 0  i lt 3. Bpm. Average Bpm. Valuesi Bpm. Average 5                                       Divide by 3. XXX. X since update is a multi byte transfer, disable interrupts until its doneno. Interrupts Display. Value Bpm. Average interrupts  given the pot value beats per minute read in, calculate the Idle. Period msec this value is used by the Timer. Beats. Per. Minute floatBpm 1. Interrupts Idle. Period unsigned intfloat6. Beats. Per. Minute floatNum. Samples interrupts delay2. Timer. 2 Interrupt Service Routine Interrupt Service Routine ISR for Timer.