uart vs sio differences ?
mike at sentex.net
Mon Dec 8 19:06:53 UTC 2008
At 01:49 PM 12/8/2008, Marcel Moolenaar wrote:
>On Dec 8, 2008, at 8:21 AM, Mike Tancsa wrote:
>>Unfortunately, we only control the FreeBSD side of things and the
>>other end of the serial connection is a windows app we dont
>>control. Everything seems to work ok from our side, but the other
>>side which we dont control seems to be missing some things we are
>>sending it and vice versa.
>It looks to me that flow-control is disabled, is that right?
>Not only does uart(4) make use of the larger buffer of the
>hardware, it's also more efficient under puc(4) than sio(4)
>is because of the use of the serdev I/F. It's possible that
>the receiver can not keep up when uart(4) is used. A serial
>line analyzer should tell you more...
Yes, flow control is supposed to be disabled. When we hook
up a serial line analyzer, the behaviour is rather odd. We only use
1200bps, so I dont think its a speed issue. Also, as part of the
protocol, we poll the other side. We send a 3 byte poll, which the
Windows side always sees, and it sends us back a 1 byte answer, which
we see fine. However, when the Windows side has "something to say",
it will send a different 1 byte response (which we get) and then the
data, which is approximately 100 to 200 bytes which we only get about
30 bytes of.
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