Hi,
> Hopefully, pin 12 provides enough current to power a MAX232 (but I'm
> afraid that 10mA may be not sufficient), and hopefully the voltage at
> pin 12 doesn't drop below 4.5V under load, (due to the diode, assuming
> that possibly Va = 5V, and not the voltage at pin 12), otherwise we're
> outside the required supply voltage range for the MAX232 (4.5...5.5V).
Should be sufficient, i think. If not, there's lot's of
low-power (and low voltage) variants of the MAX232 available,
some of which also require smaller capacitors, so one can use
0.1µF ceramics.
> Alternatively, it may be possible to interface the four signals to the
> parallel port (standard parallel port, not ECP or EPP) without needing
> any active components, but possibly just a pull-up resistor for "Data".
True, although parallel ports are dying out even faster than
serial ones. ;-)
> Another issue to consider is the availability of software interfaces
> provided by the OS to access the RS232 modem control lines or to access
This is not a problem (with ordinary user-level privileges),
every serial terminal program needs to use the handshake
lines, after all. Both Windows and Unix/Linux systems provide
API's for serial port access.
I'd guess that Graeme is quite familiar with them, since argyll
supports serial port devices. :-)
There's also a cross-platform Java library (rxtx) for seria
port access.
Regards,
Oliver
