sw: Fix RAM boot detection#331
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Up until now, docs said that RAM boot happens, when foboot finds `0x17ab0f23` in first 56 bytes of loaded binary. That wasn't the case, it was checking only first 12 bytes. `for` loop did at most `(max_check/4)-1` iterations, which is equal to 15, because `max_check` has the value of `rx_buffer` size from usb-dev.c. 15 times 4 byte words results in 60 checked bytes, but there was also division by 4 when accessing items of `dfu_buffer`, which reduced number of checks to 3. I also corrected the docs from 56 checked bytes to 60.
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Up until now, docs said that RAM boot happens, when foboot finds
0x17ab0f23in first 56 bytes of loaded binary.That wasn't the case, it was checking only first 12 bytes.
forloop did at most(max_check/4)-1iterations, which is equal to 15, becausemax_checkhas the value ofrx_buffersize from usb-dev.c, which is 64 bytes.15 times 4 byte words results in 60 checked bytes, but there was also division by 4 when accessing items of
dfu_buffer, which reduced number of checks to 3 resulting in 12 bytes checked.I also corrected the docs from 56 checked bytes to 60.