Possible to achieve similar behaviour as Nordic BLE UART with only one characteristic

[sijohans]

Hello,

I have a question regarding BLE characteristics and bi-directional communication. Assume a service like Nordic UART Service (NUS) is used, then there are two characteristics:

• One for TX (peripheral sends data by writing to the characteristic and the central receive notifications)
  • Has the notify property
• One for RX (peripheral receives data when the central write to the characteristic)
  • Has the write without response property

Also, data packages that are longer than the MTU will be sent so they are chunked into packages as large as the effective MTU size.

If a connection is established and the central has written to the CCCD to enable notifications, both the central and peripheral may initiate a data transfer "at any time" (as viewed from the application). My question is if it would be possible to achieve this with only one characteristic that has both the properties notify and write without response.

Regards

[Andy]

Yes it's possible.

[sijohans]

Thank you,

Do you know why the Nordic UART Service uses two characteristics if it is possible with one? By bi-directional i mean as good full-duplex that can be achieved with BLE.

[Andy]

I don't think you can achieve full-duplex communication over BLE. I think they just did it to make it clear that one characteristic is RX and another is TX.

But if you really want to know the reason behind it I guess you'll have to wait for a Nordic guy to answer.

[sijohans]

Yes, i guess each one have their time slot to send stuff. But at least from the application point of view we it might be able to look like full-duplex ;)