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microsoft / CFU

Component Firmware Update
MIT License
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What is the maximum payload size that CFU can support? - From Cypress Semi #49

Open ashwinnaircy opened 3 years ago

ashwinnaircy commented 3 years ago

In CFU Protocol Specification, Table 5.5 3 (FIRMWARE_UPDATE_CONTENT Header Bits) Data length field is limited to 8 bits in size. It is also mentioned that "maximum allowed value for the length is 52 bytes".

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Does this mean that the maximum allowed size in one payload transaction is 52 bytes?

samtertzakian commented 2 years ago

Sorry for delay in answering this question.

The 52-byte limitation is to allow compatibility with usb full-speed protocol. Transfer size is 60 minus 8 bytes overhead which equals 52 bytes.

Since the transfer occurs in the background, it is ok if the transfer takes a long time. There is no limit to the number of transfers.