Problem when using "pc-ble-driver-js", sending a large file to peripheral

[Eric YY]

Hi,

I'm using the  "pc-ble-driver-js" to implement a central on PC, trying to send a file through a Write w/o Response characteristic to a device. It's OK for a small file (eg. 4KB), but when I try to send a  large file, it will break randomly, eg. after several tenth KB.

The error message is: Failed to write to attribute with handle: 23: Timed out when waiting for BLE_EVT_TX_COMPLETE. 

After occurs, the connection keep but any other message (no matter short or long) will not be send to device, unless I disconnect and reconnect it.

I'm using the NodeJS 8.15.1, PCA10031 dongle with v2 SD_API_VERSION.

This is what I send the data out, anything I did it wrong? Thanks

async function sendBurst(data)

{

    let offset = 0;

    let seq = 0;

    let txBuf;

    let i;

    while (true)

    {

        i = data.length - offset;       // no. of byte need to send in this round

        // Prepare the txBuf[]

        if (offset === 0)

        {

            // First packet

            if (i > 20)

                i = 20;

            txBuf = data.slice(0, offset + i);

            txBuf[0] = (data[0] & 0x0f) | (seq << 4);       // insert "seq" into [CMD1]

        }

        else

        {

            // Remaining Packet

            if (i > 19)

                i = 19;

            txBuf = data.slice(offset, offset + i);

            txBuf.unshift(seq << 4);        // insert "seq" into txBuf[0]

        }

        seq ++;

        if (seq >= 7)

            seq = 1;

        offset += i;

        if (offset >= data.length)

        {

            txBuf[0] |= 0x80;

            seq = 0xff;

        }

        // Send it now

        await new Promise((resolve, reject) => {

            adapter.writeCharacteristicValue(charID_burstTx, txBuf, false, (err) => {

                if (err)

                {

                    reject(err);

                    return;

                }

                resolve();

            });

        });

        if (seq == 0xff)

            break;          // abort if all send

    }

}

[Eric YY]

Thanks tsec,

Seems you're right, I send the data too quickly, I don't know why but if I add 10ms delay between each writeCharacteristicValue(), the problem gone. But I meet another throughput problem, seems the implementation of the writeCharacteristicValue() is not alright for my application.

[tesc]

Hi,

What I meant was that when you get that error, you wait a few ms, then try again. You do not need to wait between each writeCharacteristicValue(), you only have to wait (and then retry) when you get the waiting for BLE_EVT_TX_COMPLETE error.

Regards,
Terje