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.