[RTTY] Windows API Question ...

[Al Kozakiewicz]

My knowledge is real rusty here,  Caveat emptor.

If I understand what you're looking for, the Win 32 serial port class uses a USHORT (unsigned 16 bit integer) data type to hold the "settable stop parity" word, which is both the number of stop bits and the byte parity. It is essentially a flag word and the bit SERIAL_STOPBITS_15 indicates the number of stop bits is 1.5. I'm also 99% sure there is a mask word that tells you what the capabilities of the device are, which tells you what parameters you can set.  In any event, the actual configuration classes do not make you do bitwise logical "ORs" to set parameters, but use whatever data type is convenient, e.g.  WIN32_SerialPortConfoguration uses a string to set the number of stop bits.

Also, I believe baud rate is represented by a ULONG, or 4 byte integer.  It is a combination of a mask word for standard baud rates as well as user programmable rates.  I do not know offhand how fractions are represented in the user programmable segment, but I do note that 134.5 is a "standard" baud rate.

In any event, it's not likely to be an OS limitation per se but a device/device driver limitation if anything.

Al
AB2ZY

-----Original Message-----
From: RTTY [mailto:rtty-bounces at contesting.com] On Behalf Of Joe Subich, W4TV
Sent: Sunday, December 28, 2014 12:37 PM
To: MMTTY at yahoogroups.com; RTTY
Subject: [RTTY] Windows API Question ...


Can someone with knowledge of Windows internals tell me if the MODE command (or the API equivalent) uses data type INTEGER for the number of stop bits on a serial port?

We know that the baud rate is type integer - thus a serial port being used for RTTY actually operates at 45.00 baud (+/- system or UART clock accuracy).  However, my testing with several UART boards seems to show operation predominately with either 1 or 2 stop bits and I'm beginning to suspect an OS limitation.

The microHAM UART in DK II, MK II, MK2R+ and micro2R avoids an OS issue by aliasing 45 baud to 45.45 and always using 1.5 stop bits for 5 bit codes.

73,

    ... Joe, W4TV

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