On 4 Jul 2003 23:21:05 -0700, (R C) wrote:

I'm working on a telemetry board and wish to include software FSK1200
(MX-614's are getting harder to find). The official Bell 202 spec is
out of print and hard to find as well, so I pieced this together from
what I can find. Multimon won't decode the output, so I'm likely doing
something wrong.

What is this Multimon thing expecting ?

Is it expecting ordinary asynchronous characters ?

// LSB first. Start bit MARK end bit SPACE
// MARK is 1, SPACE is 0

for (i = 0; i 10; i++)
{
if (i == 0)
bit = 1;
else if (i == 9)
bit = 0;
else
bit =( a (i-1)) & 0x1;

In that case I assume you have mixed the polarity of the start and
stop bits.

In ordinary RS-232 asynchronous communication the start bit is "0"
SPACE, interrupting the idle MARK state, followed by the data bits
with LSB sent first. The stop bit is "1" or MARK, which then transfers
to a MARK idle state if no more characters are to be transmitted.

If that Multimon thing is expecting AX.25, don't forget to add the bit
stuffing in the last stage before transmission.

Paul OH3LWR