Abstract
The transmitter clocks a never-ending bit stream into its transceiver’s synchronous direct mode. The stream is a back-to-back sequence of fixed blocks (330 bits, 3000 a second, 4-GFSK at about 1 Mb/s in the embodiment), each carrying its own sync word and a sequence (“period”) field in band, then its payload and a few guard bits. There are no packet headers and no gaps: every period carries audio, and control messages ride inside the blocks. The receiver’s transceiver runs in synchronous direct receive with its data and recovered clock on pins. A host-side bit port (a programmable I/O state machine or a FlexIO shifter, with DMA) counts the transceiver’s clock edges and moves 32-bit words into a RAM ring; a software deframer finds block boundaries by correlating the sync word, confirms them one block later, tolerates bit errors in the sync word, corrects small bit slips, remembers its grid across short losses, and recovers the absolute period from the per-block field. On the Si4463 the raw 4-GFSK receive became bit-exact once the AFC’s feedback to the PLL was disabled (MODEM_AFC_GAIN bit 15 cleared, 0x8FFF to 0x0FFF). On the Silicon Labs EFR32FG23 the same method is arranged on its radio library’s synchronous direct mode (data in, data out and data clock on pins, TX and RX), in which the demodulator drives the pins without the CPU in the path.
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Recommended Citation
Anonymous, "Continuous low-latency audio stream through a transceiver's synchronous direct mode: in-band framed fixed blocks, no packet headers or gaps, and a host deframer clocked by the transceiver", Technical Disclosure Commons, ()
https://www.tdcommons.org/dpubs_series/12128