Messages in this thread | | | From | "Stuart MacDonald" <> | Subject | RE: Serial port blues | Date | Sun, 21 Jan 2007 00:09:39 -0500 |
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From: On Behalf Of Joe Barr > I'm forwarding this post by the author of a great little program for > digital amateur radio on Linux, because I'm curious whether or not the > problem he is seeing can be resolved outside the kernel.
From: w1hkj [mailto:w1hkj@w1hkj.com] > I am now convinced that the current serial port drivers > available to us > on the Linux platform WILL NOT support CW and/or RTTY that is > software > generated in a satisfactory manner.
I don't know what FSK/CW/RTTY/BAUDOT is.
> Direct access to the serial port(s) is a kernel perogative in Linux. > Only kernel level drivers are allowed such port access.
Not true.
> Until such time as new information becomes available I am going to > comment out all references to CW and / or FSK via RTS/DTR. I also > question how useful the FSK on TxD (UART derived) might be to > most users > since the 45.45 baudrate is not available in the serial port driver. > That function will also be commented out.
You may be confusing the old-style baud rate lookup table (B9600 et al) with the actual capabilities of the serial port. The lookup table has a limited number of baud rates. You can get more rates than that using a custom divisor. Most motherboard-based serial ports are clocked at 1.8432 Mhz. The UART does 16 samples per bit time, yielding a max baud rate of 115200.
115200 / 25 yields 4608, which is a 1.4% error rate from 4545. This may or may not be acceptable. 115200 / 2535 yields 45.44, which is a 0.01% error rate, which is likely acceptable.
> Sorry folks, but we win some and lose some.
We make serial port boards with very flexible UARTS. 4545 exactly is achievable. 45.45 too. Linux supported.
..Stu
-- We make multiport serial products. http://www.connecttech.com/ (800) 426-8979
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