Re: CM11 Status Request (C# Language)

[nobody@xxxxxxxxxxxx (Dave Houston)]

Charles Sullivan <cwsulliv@xxxxxxxxxxxx> wrote:

>All the USB->Serial adapters I've tested (I have five) implement at least
>some modem control lines.  The cheapest I have is a $10 model from
>www.byterunner.com; the most expensive a $40 Keyspan USA-19HS.  The chips
>represented among these (as identified by the Linux drivers) are an older
>Prolific PL2303, a newer Prolific PL2303 (in the $10 model), an FTDI
>FT232BM, and whatever chip Keyspan uses.
>
>I've used all five in Linux to actuate a CM17A Firecracker with the RTS/DTR
>lines, and I've started using the RI line to detect pending incoming PLC
>signals from the CM11A.  The only problems I've encountered appear to be
>Linux-related: When used with the latest Linux 2.6.18 kernel the RI line
>on the older PL2303 chip models gets stuck in the active state and the
>Keyspan doesn't work at all.  But both work fine with earlier kernels.
>(Bug reports have been filed.)
>
>I can't say what may or may not be implemented with Windows drivers, and
>granted, there may be timing issues with the control lines when one of
>these adapters is used to connect to a high-speed modem, but that's
>not something I've tested.

I think most of the chips used (FTDI, Prolific, Silicon Labs) have all the
lines but not all adapters implement them. Keyspan is the name most often
mentioned as failing. This may be because they were originally more Mac
oriented where there really were no true RS232 ports.

The timing issue is inherent. I garbled the explanation but two translations
have to be made for each transmission. On the PC end, the driver has to
translate to/from serial & USB. On the device end, the hardware has to do
the same translations. So, while the transport via USB is fast, the overall
speed is actually slower than it would be for an RS232 link. This really
becomes apparent when downloading firmware to an embedded device that has a
serial bootloader.

http://davehouston.net
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