How to synchronize processing of received BLE data to prevent overwrites

RE: How to synchronize processing of received BLE data to prevent overwrites

Simonr — Wed, 04 Dec 2019 10:34:17 GMT

Hi Dave

What exactly in your process is it that's going slowly now? In order to make sure your writing procedure doesn't get overwritten you'll have to give some sort of signal in order to let the next command being written.

Best regards,

Simon

RE: How to synchronize processing of received BLE data to prevent overwrites

SleepingDog — Tue, 03 Dec 2019 21:54:10 GMT

I've changed the implementation so that once I've parsed and processed the JSON command I write a zero into the first byte of commandJSON. On the app side I read the command characteristic after I've written the JSON command to it to look for the zero byte and when I see it I know that the previous command has been processed and I can go ahead and send the next command. This works in that it synchronizes the writing of commands and the processing of them however it is extremely slow.

I figure there must be a better way.

I thought about moving data into a circular buffer from the commandJSON buffer so that it is removed quickly but I still would not be guaranteed that it doesn't get overwritten before I complete the transfer to the circular buffer.

RE: How to synchronize processing of received BLE data to prevent overwrites

SleepingDog — Tue, 03 Dec 2019 17:08:10 GMT

Thanks for the reply.

Are you suggesting I use a second characteristic to allow the App to be notified when it is okay to send another command?

Dave

RE: How to synchronize processing of received BLE data to prevent overwrites

Simonr — Tue, 03 Dec 2019 13:17:21 GMT

It shouldn't be possible for a command to override "itself" like this. What I think is happening, is that when you are processing the JSONcommand, your application thinks that the on_write function is finished, and sends the next one. You should add a check of some kind that makes sure that you're finished parsing the first command before calling the on_write(); function again. So add a WAIT_FOR_FINISHED check that confirms that whatever the last function that finishes up processing your command is complete.

Best regards,

Simon