Initial commit

.gitignore

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+.pio
+.pioenvs
+.piolibdeps
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+.vscode/launch.json

.travis.yml

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+# Continuous Integration (CI) is the practice, in software
+# engineering, of merging all developer working copies with a shared mainline
+# several times a day < https://docs.platformio.org/page/ci/index.html >
+#
+# Documentation:
+#
+# * Travis CI Embedded Builds with PlatformIO
+#   < https://docs.travis-ci.com/user/integration/platformio/ >
+#
+# * PlatformIO integration with Travis CI
+#   < https://docs.platformio.org/page/ci/travis.html >
+#
+# * User Guide for `platformio ci` command
+#   < https://docs.platformio.org/page/userguide/cmd_ci.html >
+#
+#
+# Please choose one of the following templates (proposed below) and uncomment
+# it (remove "# " before each line) or use own configuration according to the
+# Travis CI documentation (see above).
+#
+
+
+#
+# Template #1: General project. Test it using existing `platformio.ini`.
+#
+
+# language: python
+# python:
+#     - "2.7"
+#
+# sudo: false
+# cache:
+#     directories:
+#         - "~/.platformio"
+#
+# install:
+#     - pip install -U platformio
+#     - platformio update
+#
+# script:
+#     - platformio run
+
+
+#
+# Template #2: The project is intended to be used as a library with examples.
+#
+
+# language: python
+# python:
+#     - "2.7"
+#
+# sudo: false
+# cache:
+#     directories:
+#         - "~/.platformio"
+#
+# env:
+#     - PLATFORMIO_CI_SRC=path/to/test/file.c
+#     - PLATFORMIO_CI_SRC=examples/file.ino
+#     - PLATFORMIO_CI_SRC=path/to/test/directory
+#
+# install:
+#     - pip install -U platformio
+#     - platformio update
+#
+# script:
+#     - platformio ci --lib="." --board=ID_1 --board=ID_2 --board=ID_N

.vscode/extensions.json

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+{
+	// See http://go.microsoft.com/fwlink/?LinkId=827846
+	// for the documentation about the extensions.json format
+	"recommendations": [
+		"platformio.platformio-ide"
+	]
+}

include/README

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+
+This directory is intended for project header files.
+
+A header file is a file containing C declarations and macro definitions
+to be shared between several project source files. You request the use of a
+header file in your project source file (C, C++, etc) located in `src` folder
+by including it, with the C preprocessing directive `#include'.
+
+```src/main.c
+
+#include "header.h"
+
+int main (void)
+{
+ ...
+}
+```
+
+Including a header file produces the same results as copying the header file
+into each source file that needs it. Such copying would be time-consuming
+and error-prone. With a header file, the related declarations appear
+in only one place. If they need to be changed, they can be changed in one
+place, and programs that include the header file will automatically use the
+new version when next recompiled. The header file eliminates the labor of
+finding and changing all the copies as well as the risk that a failure to
+find one copy will result in inconsistencies within a program.
+
+In C, the usual convention is to give header files names that end with `.h'.
+It is most portable to use only letters, digits, dashes, and underscores in
+header file names, and at most one dot.
+
+Read more about using header files in official GCC documentation:
+
+* Include Syntax
+* Include Operation
+* Once-Only Headers
+* Computed Includes
+
+https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html

lib/README

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+
+This directory is intended for project specific (private) libraries.
+PlatformIO will compile them to static libraries and link into executable file.
+
+The source code of each library should be placed in a an own separate directory
+("lib/your_library_name/[here are source files]").
+
+For example, see a structure of the following two libraries `Foo` and `Bar`:
+
+|--lib
+|  |
+|  |--Bar
+|  |  |--docs
+|  |  |--examples
+|  |  |--src
+|  |     |- Bar.c
+|  |     |- Bar.h
+|  |  |- library.json (optional, custom build options, etc) https://docs.platformio.org/page/librarymanager/config.html
+|  |
+|  |--Foo
+|  |  |- Foo.c
+|  |  |- Foo.h
+|  |
+|  |- README --> THIS FILE
+|
+|- platformio.ini
+|--src
+   |- main.c
+
+and a contents of `src/main.c`:
+```
+#include <Foo.h>
+#include <Bar.h>
+
+int main (void)
+{
+  ...
+}
+
+```
+
+PlatformIO Library Dependency Finder will find automatically dependent
+libraries scanning project source files.
+
+More information about PlatformIO Library Dependency Finder
+- https://docs.platformio.org/page/librarymanager/ldf.html

platformio.ini

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+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[env:esp32dev]
+platform = espressif32
+board = esp32dev
+framework = arduino

src/data.cpp

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+#include <BLEUtils.h>
+#include <math.h>
+#include <Arduino.h>
+#include "data.h"
+
+inline int min(int a, int b) { return ((a)<(b) ? (a) : (b)); }
+
+/*
+
+The data schema is:
+
+- 2 bytes sequencing header:
+  - byte 1: stroke number (0-255, cycles back to 0)
+  - byte 2: reading number (0-255 max, will give 2.5 seconds at 50Hz)
+- 18 bytes of data
+
+totalling the maximum of 20 bytes per GATT packet.
+
+We'll still break down 
+
+*/
+
+void sendData (uint8_t data[], int stroke_index, int size, BLECharacteristic* pCharacteristic) {
+  int index = 0;
+  int tx_index = 0;
+  int packet_index = 0;
+  uint8_t tx_buffer[BLE_MAX_BYTES];
+
+  // TODO: need to add current time (millis) and length of packet to buffer
+
+  while (index < size) {
+    // Set the header bytes in the tx_buffer
+    packet_index += 1;
+    tx_buffer[0] = stroke_index;
+    tx_buffer[1] = packet_index;
+    tx_index = BLE_HEADER_BYTES;
+
+    // Transfer a chunk of payload data to the tx_buffer
+    for (int i=index; i<min(index + BLE_PAYLOAD_BYTES,size); i++) {
+      tx_buffer[tx_index] = data[index];
+      tx_index++;
+    }
+
+    // Send the buffer
+    pCharacteristic->setValue(tx_buffer, BLE_MAX_BYTES);
+    pCharacteristic->indicate();
+
+    // Increment the readings buffer index 
+    index += BLE_PAYLOAD_BYTES;
+
+    delay(20); // bluetooth stack will go into congestion, if too many packets are sent
+  }
+}

src/data.h

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+
+
+#ifndef HEADER_DATA
+#define HEADER_DATA
+
+#define BLE_DATA_LENGTH 2
+#define BLE_HEADER_BYTES 2
+#define BLE_MAX_BYTES 20
+#define BLE_PAYLOAD_BYTES 18
+#define MIN_READINGS 50
+#define MAX_READINGS 100
+
+//Prototype for data helper functions found in data.cpp
+void sendData (uint8_t data[], int stroke_index, int size, BLECharacteristic* pCharacteristic);
+
+#endif