On Fri, Jun 17, 2016 at 2:41 PM, Neil wrote: > Memory can be volatile, as the data will be retrieved after the logs are > done, and the memory does not need to be retained after that. I will > probably have to put in a battery backup or similar, but that's > relatively easy. > > "rugged" means it will get shaken quite a bit, so the > connector/connection to the microSD card is what I'm worried about. I do > have some push-pull microSD connector samples on the way, but will have > to test. > > This will be for for a portable/mobile device. WiFi is not an option, > as well as directly sending the data to some other device. It's going to > have to be quite compact. FWIW though, I recently investigated various > wireless options for another project and WiFi modules (especially the > lower-cost ones like the ESP8266) are really power-hungry. For on-going > data transmission, you should look into the nRF24L01 which can be had > for less than a buck nowadays. I understand it's good on power > consumption, but have to investigate that still. > > Up to this point, I've been assuming that if I use SD/microSD it would > be removable for retrieval of the data, but perhaps I should consider > just soldering and attaching permanently to the PCB. I've seen some > hobbyist 3DP control boards do this and thought it looked hokey/amateur, > but I can probably do that and 3D-print a cover to hide it. > > Re: wear leveling, reliability is important. Shouldn't I be > uncomfortable logging data for a couple hours over 4GB or 8GB w/o any > wear leveling? FWIW, my pallpark logs will be just under 1K bytes per > second. Wear leveling is about not writing to the same memory cells over and over again. That's more of a write-read-rewrite activity. Continuously streaming more to the memory by definition has to write to different cells. You can put lots of data in the memory, pull the data once and reset for the cost of ONE write cycle. What you don't want to happen is the system to write and rewrite one physical location in memory many times a second. That will cause issue. If you can find a way to shove an SD card in it, you're probably better off to look at using an existing library to manage the card. Things like FAT and wear leveling really are solved problems. Unless you're doing something esoteric or living under some restrictive license requirements or some such= .. Yes, Wifi is a fairly power hungry mechanism. Can't say I'd suggest it much for very small battery systems (no WiFi smart watches :-) ), but for larger things or mains powered devices it becomes quite appealing. For smaller battery powered stuff, my goto would likely be Bluetooth. But, as always, the "best" for a particular application depends very much on the application. There's also micro SD card sockets that are fully captive - a cage folds down and latches over the card. Should be much more vibration resistant than anything that relies on friction. -Denny --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .