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My project is to transfer an image wirelessly via BLE from my Sparkfun EDGE board using the Arduino IDE to another laptop. In the following, for simplicity, I have reduced the program to transmit integers via BLE. This already works but it takes a long time (~0.5 seconds) to transfer a few bytes. However, from the BLE specifications, much more should be possible. This is the stripped down code for the Board using Arduino:


#include <ArduinoBLE.h>
#include "utility/HCI.h"    // needed for sendcommand
#include <string>

const char BLE_PERIPHERAL_NAME[] = "Peripheral Hello World BLE";
BLEService Test("83436682-10c6-4dad-acb1-133927f3f080");
BLEStringCharacteristic HelloWorlds("83436682-10c6-4dad-acb1-133927f3f080", BLERead | BLENotify, 512);


#define SERIAL_PORT Serial
#define BAUD_RATE   115200 //(originally, 460800)


void setup() {


// Start up serial monitor
  SERIAL_PORT.begin(BAUD_RATE);


#ifdef BLE_Debug
  BLE.debug(SERIAL_PORT);         // enable display HCI commands
#endif
  BLE.setLocalName(BLE_PERIPHERAL_NAME);
  BLE.begin();


BLE.setAdvertisedService(Test);


Test.addCharacteristic(HelloWorlds);


BLE.addService(Test);
  BLE.advertise();
//BLE part end
  }


void loop(){
    int period=3000; //minimum time [ms] to be spent in each loop. This is to give the BLE enought time to transmit. To be adjusted depending on the test.
    unsigned long timing=millis();


BLE.poll();

int v1;
v1 = rand() % 100; 

//Generate 8 integer to be transmitted
String sixteen=String(v1);
for (uint32_t ccc=0; ccc &lt; 8; ccc=ccc+1){

  v1 = rand() % 100; 
  sixteen = sixteen + &quot; &quot; +String(v1);      
}



HelloWorlds.writeValue(sixteen);
  SERIAL_PORT.print(sixteen);
  SERIAL_PORT.print("   ");


while(millis() < timing + period){
   }


}

The code compiles, runs on the EDGE board and I receive the random bytes on my phone (NRF app) as well as on the other laptop. On the other laptop, I use gatttool in the Ubuntu terminal to receive the packets:

gatttool -I
connect C0:4B:39:C9:B1:04
char-read-hnd c

(I obtain the handle "c" through inspecting the characteristics before). Then, I do receive the String, but it takes the some hundreds of milliseconds until the integers are displayed. I also automated this in a Python script using pexpect and then print the timestamps after the sendline and expect command and it shows the time difference of ~hundreds of milliseconds.

The data rate that I target should be at least hundreds of bytes per second.

Thank you kind community.

Bene Gesserit
  • 21
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0 Answers0