Characteristic length being truncated when sent as notification.

[jhewitt]

I have a custom profile containing five custom characteristics.

The largest characteristic is 256 bytes in size and can be read reliably by an iPhone.

When it is sent as a notification however, it is being truncated reliably at 182 bytes.

I am receiving no errors in the call to sd_ble_gatts_hvx() and it is returning the correct length value of 256.

What is causing the value to be truncated when sent as a notification but not when read by the central device directly?

[Andy]

Your iPhone's ATT MTU is 185. You have 3 bytes of overhead and that's why you only receive 182 bytes. You'll have to come up with a different strategy to send all the data you need.

For example, you could send a series of notifications and parse them as needed on your app.