Protocol 7.00 Screenstreaming communication flows#

Screenstreaming with Protocol 7.00 involves a sender and a receiver. The objective with this protocol is for the sender to be able to send frames as they are produced to the receiver.

Except for a conditional acknowledgement at the beginning of the flow, the receiver does not send anything, and in case of invalid checksum, it discards such packets.

The communication schema is the following:

sequenceDiagram Participant sender as Sender<br />(Calculator) Participant receiver as Receiver<br />(PC, ...) alt Sender requires acknowledgement from the Receiver sender->>receiver: Check packet receiver->>sender: Acknowledgement packet end loop Screenstreaming is active sender->>receiver: Frame packet end

Warning

Sometimes, due to the high volume of data, a few bytes can be skipped here and there, leading to a desynchronization on the input stream. It is recommended, on the receiving function, to add an option to find the beginning of the next screenstreaming packet, to fix such desynchronized inputs.

Acknowledge a Sender#

On certain conditions, such as when the ScreenRecv(XP) mode is used on the fx-CG50, the sender requires acknowledgement from the receiver. As such, it will continuously send check packets, such as the following one:

16 43 41 4c 30 30 44 30  .CAL00D0

In such cases, the receiver must answer with the following acknowledgement packet:

06 30 32 30 30 31 30 44  .020010D

Once the sender has received acknowledgement, it will start sending frame packets.

For more information, see 0x16 – Check packet and 0x06 – Acknowledgement packet.