Bas van Dijk wrote:
> Hello,
>
> I'm trying to understand how the baudrate divisor and subdivisor are
> encoded in the value and index fields of a 'SIO_SET_BAUDRATE_REQUEST'
> control request.
>
> I looked at the 'ftdi_convert_baudrate' function which does the actual
> encoding but failed to understand how the encoding really works.
>
> What I basically want to know is given a divisor for example: 3 and
> subdivisor: 0.125 (1/8) how these values are encoded in the value and
> index fields.
x = 32-bit temporary register
The divisor is stored directly in x[13..0]
The subdivisor is encoded into x[16..14] using the mapping in AN232B-05
value[15..0] is from x[15..0]
index[15..0] is from x[31..16]
except on ft2232c, where:
index[15..8] is from x[23..16]
index[7..0] is the interface number
Check the libftdi source and ftdi_sio.c Linux driver for examples
-jim
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