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https://github.com/RfidResearchGroup/ChameleonUltra.git
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Philippe Teuwen
30 lines
1.9 KiB
Markdown
30 lines
1.9 KiB
Markdown
# Protocol description
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**WIP**
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## Packets format
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The communication with the application is not the easiest but is structured as follows:
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- **SOF**: `1 Byte`, the "Magic Byte" represent the start of a packet, must be `0x11`.
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- **LRC1**: `1 Byte`, the LRC ([**L**ongitudinal **R**edundancy **C**heck](https://en.wikipedia.org/wiki/Longitudinal_redundancy_check)) of the `SOF`, must be `0xEF`.
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- **CMD**: `2 Bytes` in unsigned [Big Endian](https://en.wikipedia.org/wiki/Endianness) format, each command have been assigned a unique number (e.g. `factoryReset(1020)`), this is what you are sending to the device.
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- **STATUS**: `2 Bytes` in unsigned [Big Endian](https://en.wikipedia.org/wiki/Endianness) format. If the direction is from APP to hardware, the status is always `0x0000`. If the direction is from hardware to APP, the status is the result of the command.
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- **LEN**: `2 Bytes` in unsigned [Big Endian](https://en.wikipedia.org/wiki/Endianness) format, the length of the data, maximum is `512`.
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- **LRC2**: `1 Byte`, the LRC ([**L**ongitudinal **R**edundancy **C**heck](https://en.wikipedia.org/wiki/Longitudinal_redundancy_check)) of the `CMD`, `STATUS` and `LEN`.
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- **DATA**: `LEN Bytes`, the data to send or receive, maximum is `512 Bytes`. This could be anything, for example you should sending key type, block number, and the card keys when reading a block.
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- **LRC3**: `1 Byte`, the LRC ([**L**ongitudinal **R**edundancy **C**heck](https://en.wikipedia.org/wiki/Longitudinal_redundancy_check)) of the `DATA`.
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The total length of the packet is `LEN + 10` Bytes. For receiving, it is the exact same format.
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Note: LRC2 and LRC3 can be computed equally as covering either the frame from its first byte or from the byte following the previous LRC, because previous LRC nullifies previous bytes LRC computation.
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E.g. LRC3(DATA) == LRC3(whole frame)
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## Packet payloads
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Each command and response have their own payload formats.
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TODO:
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