36 lines
1.1 KiB
Plaintext
36 lines
1.1 KiB
Plaintext
STC15 series USB ISP protocol
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=============================
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- host does OUT and IN control transfers for write and read
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- IN transfer with wLength = 132, wValue = 0, wIndex = 0, bRequest = 0 are used for all reads
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- OUT transfers with arbitrary size are used for writes
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- packets from MCU
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always start with 0x46 0xb9, similar to serial protocols
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third byte is packet length
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followed by data bytes
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8 bit checksum at the end, looks like 8 bit modular subtraction
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- packet types
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most likely derived from the serial protocol, at least partially
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info packet
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- same as with serial protocol
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option packet
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- generally same as with serial protocol, some header stuff omitted
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- flash data
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wIndex specifies write address
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wValue is 0xa55a
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bRequest is 0x22 for first packet, 0x02 for the following ones
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unusually encoded: a total of 128 bytes per packet, with every 7 byte checksummed in some way, for a total of 18x7 byte segments and a final 2 byte segment
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checksum: 8 bit inverted modular sum
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- option packet
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wIndex is 0
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wValue is 0xa55a
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bRequest is 4
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seems to use the same checksumming scheme
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