I am intending to purchase a used laptop to handle some instruments via bit banging. I see some have either or both parallel/serial ports and could get one without and use PCMCIA. I began reading about this and it seems everything is going through the USB yet looking like the aforementioned ports. This will not work for me as I understand there is a 125 ms time frame involved with USB, which will interfere with my bit banged code.
Can someone assure me there is a way to install true legacy parallel and serial ports in fairly recent laptops?
depends what you mean by "recent." The ibm thinkpad t23 has both ports,
as does the a31p. Perhaps you should spell out your CPU/memory/drive
requirements: are you planning to use a "desktop environment"?
Notice I said intending to buy hence cannot specify hardware. Not for desktop enviro as I have 3 of those available to me. Just looking at the used market for something 3-4 yr old. The USB is becoming not the port of choice but port of provision. One can access printer via cable adapter (& drivers) to have USB-to-Parallel port but this will not allow for me to access the port for microsecond timing due to what I am told is a 125ms frame buffer in the USB.
Thus are all new laptops constrained to use everything thru the USB or can a regular legacy parallel port be added to these puppies without a USB in the middle???
That would be very difficult since you would have to alter the motherboard. I wouldn't even think of doing it without a logic analyzer and oscilloscope. Even then, with multi-layer motherboards it may turn out to be impossible to splice into the traces you will need to. At the very least, this would be a long-term project.
If the laptop you get doesn't have serial/parallel ports (a lot still do have them, such as the Dell Latitude series), then your best bet is a PCMCIA card with them.