5 ms·
Cool project! The most interesting part, IMO, is the "SRAM with EEPROM backup" chip. It allows you to persistently save the clock hands' positions every time t
by teraflop 8mo ago
Cool project!
The most interesting part, IMO, is the "SRAM with EEPROM backup" chip. It allows you to persistently save the clock hands' positions every time they're moved, without burning through the limited write endurance of a plain old EEPROM. And it costs less than $1 in single quantities. That's a useful product to know about.
- sowbug 8mo agoI'm not sure if this is the same technology, but regardless it's also cool: https://www.adafruit.com/product/1897 https://www.adafruit.com/product/1897
- mftrhu 8mo agoNot quite - the chip the article refers to is the 47L04 [0], which is "just" NVSRAM built out of a RAM + EEPROM. I do agree on FeRAM being cool, though - I have a few I2C chips en route, and I can't wait to get my hands on them. [0] https://www.microchip.com/en-us/product/47L04 https://www.microchip.com/en-us/product/47L04
- qwertox 8mo agoThanks to both of you for bringing FRAM onto my radar!
- summa_tech 8mo agoYou could also consider MRAM. Which is available in larger sizes - up to 4 Mbit on SPI bus in the MR20H40, and 128 Mbit in EM128LXQ (but it gets unreasonably expensive when this big). https://www.everspin.com/family/mr20h40?npath=259 https://www.everspin.com/family/mr20h40?npath=259
- pjc50 8mo agoFRAM is extremely neat on paper, combining SRAM ish speeds with non-volatility, but adoption seems to be low. Possibly due to scaling issues. I've had a FRAM-based TI MSP430 in my random parts drawer for about a decade.
- ComputerGuru 8mo agoThat was my first FRAM experience, too. Good chip, good times. Insanely low power draw!
- ssl-3 8mo agoThat's really neat. TIL. So the way this works seems to be this: It's an SRAM and an EEPROM in one little package along with a controller that talks with each, with a little capacitor (this clock uses 4.7uf) placed nearby. The SRAM part does all of the normal SRAM stuff: It doesn't wear out from reading/writing, and as long as it has power it retains the data it holds. The EEPROM does all the normal EEPROM stuff: It stores data forever (on the timescale of an individual human, anyway), but has somewhat-limited write cycles. The controller: When it detects a low voltage, it goes "oh shit!" and immediately dumps the contents of the SRAM into EEPROM. This saves on EEPROM write cycles: If there are no power events, the EEPROM is never written at all. Meanwhile, the capacitor: It provides the power for the chip to perform this EEPROM write when an "oh shit!" event occurs. When power comes back, the EEPROM's data is copied back to SRAM. --- Downsides? This 47L04 only holds 4 kilobits. Upsides? For hobbyist projects and limited production runs, spending $1 to solve a problem is ~nothing. :)
- bonsai_spool 8mo agoWhat's the purpose of using an LLM to write a comment here?
- ssl-3 8mo ago"Hey, someone on the Internet used decent diction! Obviously, this means I must accuse them of being a bot!" (Hey Dang. Can we get a ban button? There's a few people here that are impossible to conduct rational discourse with. My sanity would improve if they were simply gone from my view.)
- ninalanyon 8mo agoYou could create a browser user script to do it locally.
- ssl-3 8mo agoThat's not a terrible idea. An extra UI element or two should be enough. Maybe with sticky options for collapse-by-default or hide-by-default at the top of each HN comment section. And the list of usernames can be stored and edited in the purveyor's HN bio (in plain text, like a monster), so that it works automatically across devices.
- monocasa 8mo agoI do like the frams too for similar use cases. Particularly I like that I can get those large enough to stick a ring buffer from debug out on them as well and get crash logs from embedded systems despite the debug uart not being tethered to a dev machine.
- harvie 8mo agoi think it's called EERAM, however having proper closed loop control with hand position feedback would be preferable in my opinion...
- the_fall 8mo agoMeh. The room-temperature endurance of modern EEPROMs (e.g., ST M95256) is something like 4 million cycles. If you use a simple ring buffer (reset on overflow, otherwise just appending values), you only need to overwrite a cell once every 32k ticks, which gives you a theoretical run time of 250,000 years with every-minute updates or 4,100 years with every-second updates.