lawrencejberry / heart-rate-monitor

An embedded heart rate monitor developed for the FRDM KL03 micro-controller

Heart Rate Monitor

This is a heart rate monitoring application developed for the FRDM KL03 evaluation board. It is built on a stripped-down version of the Warp firmware developed by the University of Cambridge's Physical Computation Laboratory.

Building the application

Prerequisites: You need an arm cross-compiler such as arm-none-eabi-gcc installed as well as a working cmake (installed, e.g., via apt-get on Linux or via MacPorts or Homebrew on macOS). You will also need an installed copy of the SEGGER JLink commander, JlinkExe, which is available for Linux, macOS, and Windows (here are direct links for downloading it for macOS, and Linux tgz 64-bit).

1. Compiling the application

The steps here are drawn from the compilation of the Warp firmware.

First, specify the full path to the bin directory of your arm cross-compiler in the environment variable ARMGCC_DIR by changing line 3 of build/ksdk1.1/build.sh:

export ARMGCC_DIR=<full-path-to-arm-cross-compiler>

Second, specify the full path to the application directory so that JLink can correctly locate the binary output file by changing line 3 of tools/scripts/jlink.commands:

loadfile <full-path-to-application>/build/ksdk1.1/work/demos/Warp/armgcc/Warp/release/Warp.srec

Then you should be able to compile the application with:

cd build/ksdk1.1/
./build.sh

This copies the files from Warp/src/boot/ksdk1.1.0/ into the KSDK tree, builds, and converts the binary to SREC. When editing source, edit the files in Warp/src/boot/ksdk1.1.0/, not the files in the build location, since the latter are overwritten during each build.

2. Pin configuration

The following pins on the FRDM KL03 evaluation board are connected to an SSD1331 OLED display and a MAX30105 IR sensor:

OLED display:

BOARD		DISPLAY
3.3V	->	VCC
GND	->	GND
PTA8	->	MOSI
PTA9	->	SCK
PTB13	->	OCS
PTA12	->	D/C
PTB0	->	RST

IR sensor:

BOARD		IR SENSOR
3.3V	->	VCC
GND	->	GND
PTB3	->	I2C SCL
PTB4	->	I2C SDA
PTA7	->	INTERRUPT

The interrupt pin on the IR sensor is pulled up by a 4.7k resistor.

3. Loading the application onto the evaluation board

Run the firmware downloader:

JLinkExe -device MKL03Z32XXX4 -if SWD -speed 100000 -CommanderScript ../../tools/scripts/jlink.commands

Source File Descriptions

The core of the application is in src/boot/ksdk1.1.0/warp-kl03-ksdk1.1-boot.c. The drivers for the display are in devSSD1331.c and for the IR sensor in devMAX30105.c. The section below briefly describes all the source files in this directory.

CMakeLists.txt

This is the CMake configuration file. Edit this to change the default size of the stack and heap.

SEGGER_RTT.*

This is the implementation of the SEGGER Real-Time Terminal interface. Do not modify.

SEGGER_RTT_Conf.h

Configuration file for SEGGER Real-Time Terminal interface. You can increase the size of BUFFER_SIZE_UP to reduce text in the menu being trimmed.

SEGGER_RTT_printf.c

Implementation of the SEGGER Real-Time Terminal interface formatted I/O routines. Do not modify.

devSSD1331.*

Driver for the SSD1331 OLED display.

devMAX30105.*

Driver for the MAX30105 IR sensor.

gpio_pins.c

Definition of I/O pin configurations using the KSDK gpio_output_pin_user_config_t structure.

gpio_pins.h

Definition of I/O pin mappings and aliases for different I/O pins to symbolic names relevant to the Warp hardware design, via GPIO_MAKE_PIN().

startup_MKL03Z4.S

Initialization assembler.

warp-kl03-ksdk1.1-boot.c

The core of the implementation. This puts together the processor initialization with a while loop which continuously runs the program when activated by an interrupt on PTA7.

warp.h

Constant and data structure definitions.

Acknowledgements

The Warp firmware is developed by Phillip Stanley-Marbell and the University of Cambridge's Physical Computation Laboratory. This application was developed as a final project for the 4B25 Embedded Systems course at the Cambridge University Engineering Department.