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36 lines
1.5 KiB
36 lines
1.5 KiB
# TinyFrame
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TinyFrame is a simple library for building and parsing frames
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(packets) to be sent over a serial interface (like UART). It's implemented
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to be compatible with C89 and platform agnostic.
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Frames are protected by a checksum and contain a "unique" ID,
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which can be used for chaining messages. Each peer uses a different
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value for the first bit of all IDs it generates (the "master flag"
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or "peer_bit") to ensure there are no clashes. Typically the master
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(PC, main microcontroller) will use "1" and the surrogate (WiFi module,
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USB-serial connected gadget, display driver...) uses "0".
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The library lets you bind listeners waiting for any frame, or a
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particular ID. This allows for easy implementation of async communication.
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## Frame structure
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The frame makeup is inspired by that of SBMP (my other, more complicated
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and advanced UART protocol library).
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```
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<SOF><ID><NOB><PAYLOAD><CKSUM>
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SOF ... start of frame, 0x01
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ID ... (master_flag | 7-bit counter) - the frame ID
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NOB ... nr of payload bytes in the frame (1..256)
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PAYLOAD ... NOB bytes of data, can contain any byte values 1..256
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CKSUM ... checksum, implemented as XOR of all preceding bytes in the message
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```
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The frame ID (in SBMP called "session ID") can be used to chain multiple related
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messages and maintain the context this way. For example, a response may copy
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the frame ID of the request frame, which then triggers a callback bound by the
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requesting peer. Such behavior is application specific and is thus left to the
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upper layers of the protocol.
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