Sometimes it’s nice to just enhance an existing product, especially when the supply of blank boards starts running low and more need to be ordered. I’m running low on the SD shields so it was a good time to make some improvements. This is a prototype:
The changes from the Rev 4 boards:
- A DS3231 RTC and backup battery are now on-board instead of having the plug-in RTC. Too many of those plug-in boards had batteries that died within a year or two, so I decided to just put the chip directly on the board and have a battery connector. It takes a very common LR44 battery which can be replaced easily when it fails.
- DIP switches are clearly labeled as to which is which, and which direction is on and off.
- A pull-down resistor is temporarily added here to fix a problem where the green and red LEDs don’t work right until the host computer initializes the interface to the SD shield. A pin was left floating and confused the software into thinking the host was sending a byte when it wasn’t.
- Two I2C pull-up resistors were added but do not seem to be necessary.
There will eventually be a Rev 6 with the new pull-down resistor and maybe the two pull-ups removed, but I’ll use the current Rev 5 boards and manually add the pull-down for now.
The RTC is completely software compatible with the current boards so any version of our Arduino code will work with it.
Some customers of our bare boards have a hard time trying to find some of the vintage components, so I started adding them to the store. Initially it’s just MC14411 baud rate generator, MC6875 clock generation chip and6532 RIOTs. I’ll add some more parts, but I’m really not in the parts business, these are just for people needing a few odd chips for building one of our bare boards.
A box containing 250 of the Molex connectors arrived today so now I’ll be populating lots of SS-50 boards again. They arrive in trays of 56 connectors, two of which are here:
Speaking of rebuilding my inventory, I’ll have a lot of items for show/sale at Vintage Computer Festival East in New Jersey, May 18-20. There are a few vintage computer festivals around the country, but the one in NJ is definitely big compared to the rest. Besides being a great time to see and use our products, there are dozens of excellent displays of vintage computer systems, so it’s a great chance to see a lot of the systems you missed or couldn’t afford at the time.
I’ve been using github to hold most of the engineering documents for our products, including CAD files, source code, documentation, etc. In the near future I’m going to start making some of the projects public, particularly the source code to the SD shield, our extensions to SBUG, xSWTBUG, the KIM Clone monitor, etc. Customers have noted that some of the code on the thumb drive is older than what’s actually shipped with products so it makes sense to just put the code in public git repositories so the latest is always available. I’m also hoping others will pick up the code and do more with it. Despite my enthusiasm to write code, design hardware and produce a few dozen products, I also have a day job, family, and sometimes need some down-time to play with other interests. Having the code public means others can free access to it and can put their extensions on-line for others.
This weekend I’m helping my wife with a STEM weekend at a local Girl Scout camp so the soldering iron will be turned off most of Saturday.