October 2004
Intermediate to advanced
304 pages
7h 44m
English
Content preview from PC Hacks
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Hack #78. Rewire Your COM Ports
Rewire an old COM port board to use available IRQs to run four ports simultaneously.
In this hack, we'll rewire the IRQ lines of an old 8-bit COM port card to configure COM3 and COM4 ports to use IRQs 5 and 7. Rewiring older I/O cards takes a bit of skill—specifically with hand tools and a soldering iron.
Figure 8-3 shows an obvious rewire of IRQ signals. Accomplishing this rewiring required opening the circuit traces from the IRQ 3 and 4 connection "fingers," then adding wires from the IRQ 5 and 7 "fingers" to the circuit traces that once connected to IRQs 3 and 4.
Figure 8-3. IRQ lines rewired on a COM port I/O card
If you decide to try this at home, you need to know the connector pin information to locate the respective IRQ circuit traces, which are:
| Pin B21 = IRQ7 |
| Pin B23 = IRQ5 |
| Pin B24 = IRQ4 |
| Pin B25 = IRQ3 |
The "B" designates the component side of the circuit board, as shown in Figure 8-3. Pins are counted from the bracket (off camera to the left) towards the end of the card. Pin B21 is the 21st pin from the left.
To perform this hack, you need the following tools:
A 60-watt soldering iron or a temperature-controlled soldering iron with a small 700-800 degree tip
Solder
2 to 3 inches of 22- to 26-gauge wire
Wire cutters and strippers
An X-ACTO or similar hobby knife
With the right tools at hand, follow these steps:
Power down the computer, unplug it, and remove ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.