Write long data over BLE (+ than 20 bytes)

Steps to reproduce

1. use the BLE explorer application

2. modify to send more than 20 bytes

Expected behavior

I develop a long data function sender like follow :

public async void sendDataBle(List<List<Byte>> trame)
        {
           Task isSendCompleted = new Task();
            for (Byte numPaquet = 0; numPaquet < trame.Count; numPaquet++)
            {
                await(isSendCompleted  = WriteToTXCharacteristic(trame.ElementAt(numPaquet).ToArray())));
                while (!isSendCompleted.IsCompleted) ;
            }
        }

the List<Byte> in list trame have a maximum of 20 Bytes.

I tried this implementation too :

 public async void sendDataBle(List<List<Byte>> trame)
        {
            for (Byte numPaquet = 0; numPaquet < trame.Count; numPaquet++)
            {
                await WriteToTXCharacteristic(trame.ElementAt(numPaquet).ToArray());
            }
        }

this is the writeToTXCharacteristic function :

        public async Task WriteToTXCharacteristic(byte [] dataTX)
        {
            if (_UartTXcharac.CanWrite)
                await _UartTXcharac.WriteAsync(dataTX);

            await Task.Delay(200); //try to get tempo between two characteristic write
        }

Actual behavior

When i send less than or 20Bytes, it’s ok, i receive my packet.

When i send data (more than 20Bytes), this function try to send 2 packets. I receive one of them but after that nothing, i never receive the second.

Crashlog

There are no crash log

Configuration

Version of the Plugin: 1.2.1

Platform: e.g. iOS 10 / Android 4.4

Device: e.g. Wiko raimbow 4G

[Tijgerd]

I havent seen “INITIAL_MESSAGE_PACKET” at the time I was using Xamarin so I can’t help you with that.

If you consider using my method, there are serveral ways to “mark” the chunks:

1 (I used this one and never had any “false-positive” outcomes):

• In the first part of the message, send the total number of bytes you are going to send
• Send all the chunks
• The last chunk should contain a CRC to check if all previous bytes where send correctly

2:

• Mark the start of each chunk with the chunk-number (this will reduce the maximum data-bytes you can send with each chunk but is more secure)
• You will still need to send the number of chunks you are going to send
• A CRC is still advised

Just be creative, Hope this helps!

[trix0]

@Tijgerd I have my data divided into the chunks of data. My question is: How do I mark the start and how do I mark the last chunk.

I am very confused in here, IF I look to this stackoverflow question, In the answer there is something like initial_packet[0] = BLE.INITIAL_MESSAGE_PACKET; Do I need to specify this somehow or just send data randomly and my characteristic should take care of it ?