I keep accumulating more and more hardware, and my office is beginning to overflow with boxes, tools, and wires. I need to start turning this pile of parts into an actual machine ASAP.

The first of my recent acquisitions was a replacement universal programmer, an EasyPro 90B to replace the TOP 2007 that had problems programming GALs. Yes, I’m replacing one no-name programmer from China with another, but in this case the EasyPro 90B seems to work fine. If I’d read reviews before making my original purchase, I could have saved myself a lot of hassle. The whole TOP line has received universally poor reviews, from what I’ve seen.  Both the EasyPro and the TOP programmers were ordered from www.mcumall.com, who offered to exchange the TOP programmer after I wrote about my problems in their online forums.

My second new hardware arrival was a USBMOD4 interface module, for connecting my computer to a PC via USB. It couldn’t be simpler to use. Install the driver, and it appears as an additional COM port on the PC. Connect a USB cable to the USBMOD4, launch a terminal program, and every keypress is transmitted and stored in the USBMOD4’s FIFO buffer. An output pin changes state when the FIFO has data in it, which the computer can sense and then enable the USBMOD4 to drive the next FIFO byte onto the data bus. I was able to put together a test circuit to read data from the PC using a protoboard in about 30 minutes.

The only problem I have with the USBMOD4 is that it appears to be hardwired to draw its power from the USB cable, rather than from the system’s power supply. This means that it’s “on” as soon as the USB cable is connected, regardless of whether BMOW is turned on or off. What’s worse, if I connect the USBMOD4’s power pin to BMOW’s power bus, BMOW will turn on as soon as the USB cable is connected. I need to isolate the USBMOD4’s power from the rest of the machine’s, while still allowing for data to be passed between them. This may be a little complicated. I’m assuming it’s OK to connect their grounds, even though theoretically the PC’s ground might not be at the same electrical potential as BMOW’s. The bigger problem is that the active low signal from the USBMOD4 that signals when there’s data in the FIFO will be low if no USB cable is connected, because there will be no power to it. This will make BMOW think there’s data to be read. I think I can solve this by using a pull-up resistor connected to BMOW’s +5 supply. If anyone’s ever done something similar before, I’d love to hear about it.

I also bought an HP 1631D logic analyzer off eBay, although it hasn’t arrived yet, and it was an extra cheap ($35) unit in as-is condition. It’s a combination 100MHz bandwidth digital oscilloscope and 48 channel logic analyzer. A logic analyzer records a history of the logical value (0 or 1) of a set of signals, like an address bus or data bus. It can be used to help debug hardware problems, like why a computer locks up when it reaches a certain address. Basically, it’s a hardware debugger.

I’m sure there was a point in my life (like 2 months ago) where I assumed anyone who had a personal oscilloscope in their home was the biggest nerd imaginable.