RF69 datasheet(57/81 Pages) ETC2

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RF69

Page 56

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5.5.6. Handling Large Packets

When Payload length exceeds FIFO size (66 bytes) whether in fixed, variable or unlimited length packet format, in addition

to PacketSent in Tx and PayloadReady or CrcOk in Rx, the FIFO interrupts/flags can be used as described below:

 For Tx:

FIFO can be prefilled in Sleep/Standby but must be refilled "on-the-fly" during Tx with the rest of the payload.

1) Prefill FIFO (in Sleep/Standby first or directly in Tx mode) until FifoThreshold or FifoFull is set

2) In Tx, wait for FifoThreshold or FifoNotEmpty to be cleared (i.e. FIFO is nearly empty)

3) Write bytes into the FIFO until FifoThreshold or FifoFull is set.

4) Continue to step 2 until the entire message has been written to the FIFO (PacketSent will fire when the last bit of the

packet has been sent).

 For Rx:

FIFO must be unfilled "on-the-fly" during Rx to prevent FIFO overrun.

1) Start reading bytes from the FIFO when FifoNotEmpty or FifoThreshold becomes set.

2) Suspend reading from the FIFO if FifoNotEmpty clears before all bytes of the message have been read

3) Continue to step 1 until PayloadReady or CrcOk fires

4) Read all remaining bytes from the FIFO either in Rx or Sleep/Standby mode

Note

AES encryption is not feasible on large packets, since all Payload bytes need to be in the FIFO at the same time to

perform encryption

5.5.7. Packet Filtering

RF69's packet handler offers several mechanisms for packet filtering, ensuring that only useful packets are made

available to the uC, reducing significantly system power consumption and software complexity.

5.5.7.1. Sync Word Based

Sync word filtering/recognition is used for identifying the start of the payload and also for network identification. As

previously described, the Sync word recognition block is configured (size, error tolerance, value) in RegSyncValue

registers. This information is used, both for appending Sync word in Tx, and filtering packets in Rx.

Every received packet which does not start with this locally configured Sync word is automatically discarded and no

interrupt is generated.

When the Sync word is detected, payload reception automatically starts and SyncAddressMatch is asserted.

Note

Sync Word values containing 0x00 byte(s) are forbidden

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