BLE
I thought I’d try the BLE subset of the assignment since my team had been thinking about ways to control a drone and BLE was one of the options we were considering.
I followed the instructions on the class website and uploaded the BLE_write program from examples
For the LED specifically, there was this code also on the class website.
/*
Based on Neil Kolban example for IDF: https://github.com/nkolban/esp32-snippets/blob/master/cpp_utils/tests/BLE%20Tests/SampleWrite.cpp
Ported to Arduino ESP32 by Evandro Copercini
*/
#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEServer.h>
// See the following for generating UUIDs:
// https://www.uuidgenerator.net/
#define SERVICE_UUID "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"
int LED_PIN = 5;
char LED_STATUS;
class MyCallbacks: public BLECharacteristicCallbacks {
void onWrite(BLECharacteristic *pCharacteristic) {
std::string value = pCharacteristic->getValue();
if (value.length() > 0) {
for (int i = 0; i < value.length(); i++){
LED_STATUS = value[i];
}
}
}
};
void setup() {
Serial.begin(115200);
BLEDevice::init("MyESP32");
BLEServer *pServer = BLEDevice::createServer();
BLEService *pService = pServer->createService(SERVICE_UUID);
BLECharacteristic *pCharacteristic = pService->createCharacteristic(
CHARACTERISTIC_UUID,
BLECharacteristic::PROPERTY_READ |
BLECharacteristic::PROPERTY_WRITE
);
pCharacteristic->setCallbacks(new MyCallbacks());
pCharacteristic->setValue("Hello World");
pService->start();
BLEAdvertising *pAdvertising = pServer->getAdvertising();
pAdvertising->start();
pinMode(LED_PIN, OUTPUT);
digitalWrite(LED_PIN, LOW);
}
void loop() {
int val = (int)LED_STATUS; // cast the char* as an int
if (val == 49) // ASCII code for the number 1
digitalWrite(LED_PIN, HIGH);
else
digitalWrite(LED_PIN, LOW);
delay(2000);
}BLE Scanner App
I downloaded the basic BLE scanner from the app store and found my device on the scanner (there were a lot of devices that showed on the device surprisingly).
I notice a 1-2 second lag between writing 1 or 0 in the app and the LED turning on and off. After getting rid of the delay, the response was almost instantaneous.
I was originally concerned about the lag in piloting something like a drone, but now that I know it’s possible for the board to be pretty responsive, the problem is getting a better UI than having to write in numbers or HEX.
One solution to being limited by having to write text or HEX is to build command packets but I don’t exactly know to what to map over as of yet.