Read Characteristic Value vs. Read Long Characteristic Values
From: Anderson Lizardo <hidden>
Date: 2011-01-25 19:07:30
Hi Brian, On the implementation you did for Long Characteristic value read, you integrated the Read Blob Request handling into the existing "Read Characteristic Value" implementation. From my understanding of the code, the read blob request is issued if the response PDU size is greater than or equal to LE ATT_MTU (23). The problem I see with this approach is that if the client knows that the characteristic value is exactly 22 bytes (which makes total PDU size equal to 23 with the opcode), a spurious read blob request (and corresponding response) is sent. How could we avoid this overhead? My idea was to separate the procedures, having a "Read Long Characteristic Value" and revert Read Characteristic Value to read only the first ATT_MTU - 1 bytes as before. For characteristic values which the client knows to be within ATT_MTU - 1 bytes (of if it only cares about these bytes at the time) it would use the latter. For cases where value length is unknown, it would use the former. This would also allow us to better map to GATT procedures and have fine control on the client implementation and on our test tool (igatttool). Any other ideas? -- Anderson Lizardo OpenBossa Labs - INdT Manaus - Brazil