I regularly back-up my Raspberry Pi storage card because it’s so easy to damage the card with an improper shutdown or some such. I back up to a Mac, and you can read how I do it here. This wasn’t much of a chore in the early days when I was working with 4GB cards, but now I use 16GB Micro SDs and I know of folks who have much, much larger storage capacities thanks to never-cheaper cards. All this means the back-up takes a long time. So I wondered if I could create a gadget to tell me the task was done, allowing me to get on with other jobs in the meantime.
The Raspberry Pi Zero may have been out for a while, but it’s proving perishingly hard to get hold off. Unless, of course, you’re right at the head of the virtual queue when the online retailers put their latest batches on sale. Still, the little micro’s scarcity isn’t stopping hackers from coming up with ingenious solutions to its other limitations — too few USB ports, primarily — and accessory suppliers from issuing add-ons.
Updated My original idea was to review the Raspberry Pi Compute Module. But the thing about the Compute Module is that it’s not an end-user product: it was designed for manufacturers looking for an ARM-based platform on which they can build devices they can sell. Unlike the Raspberry Pi itself, the Compute Module is not intended for makers or for computing hobbyists. To evaluate the Compute Module what I really needed to look at was a product based upon it.
So I waited for one.
Time was when chip makers’ processor evaluation boards were well beyond the reach of ordinary mortals. That didn’t matter, of course: ordinary mortals weren’t interested in small, nude motherboards designed to help designers of embedded systems judge a microprocessor’s suitability for the application they were working on.
Unhook a Raspberry Pi from the mains and it forgets the time and date. It’ll only get them back again if you re-connect it to the Internet or enter the data manually. As a Pi user who doesn’t keep his kit connected – I usually wire and power it up when I need it – and doesn’t always bother with the Ethernet cable when he does, I’ve been after a decent real-time clock (RTC) add-on for quite a while. An RTC allows your Pi to keep time, even when the Pi’s power is cut.
When it comes to hacking hardware there’s an easy way and there’s a hard way.
The hard way involves connecting peripherals direct to one of the standard buses supported by your Raspberry Pi, Arduino, Beaglebone or whatever. Buses like I²C, SPI, UART and 1-Wire. You’ll need to take care with your wiring: have you got the right pull-up or pull-down resistor? Is there too much capacitance in the line?