RF69 datasheet(31/81 Pages) ETC2

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RF69

Page 31

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3.4.13. Bit Synchronizer

The Bit Synchronizer is a block that provides a clean and synchronized digital output, free of glitches. Its output is made

available on pin DIO1/DCLK in Continuous mode and can be disabled through register settings. However, for optimum

receiver performance its use when running Continuous mode is strongly advised.

The Bit Synchronizer is automatically activated in Packet mode. Its bit rate is controlled by BitRateMsb and BitRateLsb in

RegBitrate.

Raw demodulator

output

(FSK or OOK)

BitSync Output To

pin DATA and

DCLK in continuous

mode

DATA

DCLK

Figure 13. Bit Synchronizer Description

To ensure correct operation of the Bit Synchronizer, the following conditions have to be satisfied:

 A preamble (0x55 or 0xAA) of 12 bits is required for synchronization (from the RxReady interrupt)

 The subsequent payload bit stream must have at least one transition form '0' to '1' or '1' to '0 every 16 bits during data

transmission

 The bit rate matching between the transmitter and the receiver must be better than 6.5 %.

Notes - If the Bit Rates of transmitter and receiver are known to be the same, the RF69 will be able to receive an

infinite unbalanced sequence (all

“0s” or all ”1s”) with no restriction.

- If there is a difference in Bit Rate between Tx and Rx, the amount of adjacent bits at the same level that the

BitSync can withstand can be estimated as follows:

- This implies approximately 6 consecutive unbalanced bytes when the Bit Rate precision is 1%, which is easily

achievable (crystal tolerance is in the range of 50 to 100 ppm).

3.4.14. Frequency Error Indicator

This function provides information about the frequency error of the local oscillator (LO) compared with the carrier frequency

of a modulated signal at the input of the receiver. When the FEI block is launched, the frequency error is measured and the

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