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Introduction
============
A heartbeat generator can be used in a digital system to ...
Features
========
Normal rhythm produces four entities – a P wave, a QRS complex, a T wave, and a U wave – that each
have a fairly unique pattern. [[1]](https://en.wikipedia.org/wiki/Electrocardiography)
For simplicity the existing heartbeat module generates the QRS complex and T wave only.
* Models QRS-Complex and T-Wave
* Average time values based on 72 bpm
* Enable input for external prescaler
General Description
===================
{width=40%}
| **Name** | **Type** | **Direction** | **Polarity** | **Description** |
|-------------|-------------------|:-------------:|:------------:|-----------------|
| clk_i | std_ulogic | IN | HIGH | clock |
: Heartbeat Generator - Description of I/O Signals
Functional Description
======================
The shape of an [electrogardiogramm](https://en.wikipedia.org/wiki/Electrocardiography) as a voltage graph over time
{width=20%}
The important QRS complex and T wave are modelled as digital pulses.
{width=80%}
Design Description
==================
A conceptional RTL diagram is shown below.
{width=60%}
The simulation result shows two full periods based on a clock period of 1 ms
{width=80%}
In more detail using cursors to display correct parameters of the QRS complex and T wave.
{width=80%}
Device Utilization and Performance
==================================
The following table shows the utilisation of both modules heartbeat_gen and cntdnmodm.
The following results are extracted from
```pure
pnr/de1_heartbeat_gen/de1_heartbeat_gen.fit.rpt
```
```pure
+--------------------------------------------------------------------------------------+
; Fitter Summary ;
+------------------------------------+-------------------------------------------------+
```
The following results are extracted from
```pure
de1_heartbeat_gen.sta.rpt
```
```pure
+----------------------------------------------------------------------------------------+
; TimeQuest Timing Analyzer Summary ;
+--------------------+-------------------------------------------------------------------+
-----------------------------------------+
; Clocks ;
+------------+------+--------+-----------+
+-----------------------------------------------------------------------------+
; Multicorner Timing Analysis Summary ;
+------------------+-------+-------+----------+---------+---------------------+
```
Application Note
================
The following test environment on a DE1 prototype board uses a system clock frequency of 50 MHz.
A prescaler is parameterised to generate an output signal with a period of 1 ms.
{width=70%}
Appendix
========
References
----------
* [Wiki: Electrocardiography](https://en.wikipedia.org/wiki/Electrocardiography)
Project Hierarchy
-----------------
### Module Hierarchy for Verification
```pure
t_heartbeat_gen(tbench)
heartbeat_gen(rtl)
```
### Prototype Environment
```pure
de1_heartbeat_gen(structure)
heartbeat_gen(rtl)
cntdnmodm(rtl)
```
VHDL Sources
------------
```vhdl
LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;
ENTITY heartbeat_gen IS
PORT (clk_i : IN std_ulogic;
rst_ni : IN std_ulogic;
en_pi : IN std_ulogic;
count_o : OUT std_ulogic_vector;
heartbeat_o : OUT std_ulogic
);
END heartbeat_gen;
```
```vhdl
LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;
USE IEEE.numeric_std.ALL;
ARCHITECTURE rtl OF heartbeat_gen IS
CONSTANT n : natural := 10;
CONSTANT zero : unsigned(n-1 DOWNTO 0) := (OTHERS => '0');
CONSTANT heartbeat_period : unsigned(n-1 DOWNTO 0) := to_unsigned(833, n);
CONSTANT qrs_width : unsigned(n-1 DOWNTO 0) := to_unsigned(100, n);
CONSTANT st_width
CONSTANT t_width
CONSTANT qt_width
SIGNAL next_state, current_state : unsigned(n-1 DOWNTO 0);
SIGNAL tc_qrs : std_ulogic; -- qrs interval
SIGNAL tc_t : std_ulogic; -- T wave
BEGIN
next_state_logic :
state_register :
-- output_logic
t_wave : tc_t <=
qrs_complex : tc_qrs <=
output_value : heartbeat_o <=
END rtl;
```
Revision History
----------------
| **Date** | **Version** | **Change Summary** |
|:----------|:-------------|:--------------------|
| May 2020 | 0.1 | Initial Release |
| April 2021 | 0.2 | Added parameterisation |
|
