iOS蓝牙BLE读取数据的最大大小

Question

I have an iOS app that reads/writes on a BLE device. The device is sending me data over 20 bytes long and I see they get trimmed. Based on the following thread

Bluetooth LE maximum transmission size

it looks like iOS is trimming the data. That thread shows the solution on how to write bigger data sizes, but how do we read info larger than 20 bytes?

Answer 1

For anyone looking at this post years later like I am, we ran into this question as well at one point. I would like to share some helpful hints for data larger than 20 bytes.

• Since the data is larger than one packet can handle, you will need to send it in multiple packets. It helps significantly if your data ALWAYS ends with some sort of END byte. For us, our end byte gives the size of the total byte array so we can check that at the end of reading.
• Create a loop that checks for a packet constantly and stops when it receives that end byte (would also be good to have a timeout for that loop).
• Make sure to clear the "buffer" when you start a new read.
• It is nice to have an "isBusy" boolean to keep track of whether another function is currently waiting to read from the device. This prevents read overlaps. For us, if the port is currently busy, we wait a half second and try again.

Hope this helps!