#qi-hardware IRC log for Tuesday, 2015-03-31

GitHub164[13j1soc] 15kristianpaul pushed 1 new commit to 06master: 02https://github.com/kristianpaul/j1soc/commit/7633b712734d149c6719c227edd0d709a23e3f1501:06
GitHub16413j1soc/06master 147633b71 15Cristian Paul Penaranda Rojas: Update to 14.6 ISE01:06
kristianpaulthat stills works :p01:08
wpwrakkristianpaul: great, eh ? :)02:29
wpwrakxiangfu: heya ! how's life ? in the last days, i made a bit of progress with anelok. after the boost converter rework, it can run on battery power. at least the basic system (MCU and OLED). so i'd recommend applying the rework to the devices you have as well.02:32
xiangfuwpwrak: great. I am slow on anelok. I will try that. 02:33
wpwrakxiangfu: we may see problems with the memory card, though. the worst-case power demand of these cards can go up to 300 mW, while the CR2032 can at best deliver a bit more than 100 mW.02:34
wpwrakwhat i don't know yet is how bad they are in real life. presumably a lot nicer than that, but only measurements will tell.02:35
wpwrakif they need more power than the battery can supply, then the current design won't work and we'll have to switch to AAA or such :-(02:35
wpwrak(current design) that is, mainly the mechanical design. the electrical side would almost be identical. to if one doesn't mind an ugly case, the same PCB could be used. at least in theory :)02:37
wpwrakfor experimenting with the memory card, i'd like to integrate some things from your code. i think it may be easiest if i just cherry-pick, so you don't have to generate pull requests. does that sound okay for you ?02:41
xiangfuYes. free feel to cherry-pick02:45
wpwrakgreat. i'll do this during the long easter weekend.02:50
DocScrutinizer05wpwrak: ((presumably a lot nicer than that)) uSD? don't bet on that, constant writes on uSD heat them up to temperatures where you start to worry08:12
DocScrutinizer05then otoh *reads* are prolly way nicer, due to operation principles08:13
DocScrutinizer05how about CR2045?08:15
DocScrutinizer05wouldn't change THAT jmuch on your design, only 1 1.3mm higher case, right?08:16
DocScrutinizer05s/ 1 / a /08:16
wpwrak(much nicer) well, the idea is to use the memory card only very infrequently, especially writes. and we can go slowly - do a sector, take a break for a few dozen milliseconds, etc.11:18
wpwrakcr2045 seems a bit on the exotic side, isn't it ? digi-key don't even have that type11:19
wpwrak2450 seems to be somewhat common. internal resistance is still pretty high, though11:25
wpwrakabout 12-15 ohm for cr2450 vs. 20 ohm for cr203211:26
wpwrakif we assume an ideal cell voltage of 2.8 V, then max power of 2032 is ~100 mW and of 2450 ~160 mW11:33
wpwrakbut yes, it could be a possibility luckily, anelok's battery holder is on a separate board, so it's very easy to accommodate other cells :)11:34
wpwraki hadn't even thought of other coins. thanks !11:34
DocScrutinizer05((much nicer)) the suspected problem case is page erase11:36
DocScrutinizer05you hardly can mitigate that11:36
DocScrutinizer05only way: provide buffer energy ("Hasso! Schlafende!") sufficient for one page erase11:37
wpwrakfor the first round of devices, i could just buffer writes in internal flash, then commit them to the memory card when there's plenty of power. not ideal, but one would hardly notice11:41
wpwrakand i did the calculations for buffering worst-case power. it should actually be possible, but you need a fat supercap for it.11:42
DocScrutinizer05http://www.zubrod-net.de/Orion/Episode-2.pdf p.711:44
wpwraknot the usual coin type or other small ones (internal resistance way too high) but there are some larger blocks that have a low resistance. not cheap, though, some USD 5+ apiece @ 1000 at digi-key11:45
wpwrake.g., this critter: http://www.digikey.com/product-detail/en/BZ055B153ZSB/478-3645-ND/104591911:45
DocScrutinizer05or you siply go for two cr2015 in series11:46
DocScrutinizer05wouldn't even need major rework in battery holder, I guess11:47
DocScrutinizer05double voltage, half the current11:48
DocScrutinizer05needs buck converter then11:48
DocScrutinizer05well, they're 'cheap'11:48
wpwrak2016 ? would need to change the converter, yes. the current one is only step-up11:49
DocScrutinizer05go for buck/boost type, should be "compatible"11:50
wpwrakresistance is the same as 2032, so one could indeed draw more juice11:51
DocScrutinizer05evidently, since you only need half the current at twice the voltage for same energy11:51
DocScrutinizer05of course, if the cr2016 had tiwce the ESR than CR2032, it would be a zero-sum equation11:54
wpwrakbut if i make major changes, i'd probably go to AAA then. ESR drops by some two orders of magnitude11:56
wpwraki actually tried to feed my current boost critter with a low voltage, but it didn't like that for some reason. may be a lab effect, though - they specifically warn about the inductance of long feed lines from the lab power supply11:59
wpwrakthe chop should be good down to 0.85 V to start, 0.5 V when running. idle current is too high, though, 0.5 mA, but there's a close cousin from TI that's much better12:02
wpwrak(lab effect) also, they're weasling in their reference circuit: the caps they specify are 4.7 uF, so they look all nice and efficient, but then they mention that this is effective capacitance, so you really need a bigger cap because real-life caps usually don't have their nominal capacitance when you actually make them do something12:04
wpwrakthat's another pending rework item. and the we'll see if the critter can handle an alcaline from the next supermarket. i mean, even logitech can do it in their mice, so how hard can it be ? ;-)12:06
DocScrutinizer05should work12:11
DocScrutinizer05well, even AAAA are too weak it seems: http://data.energizer.com/PDFs/E96.pdf12:41
DocScrutinizer05AAA prolly should work12:42
DocScrutinizer05yeah, easily http://data.energizer.com/PDFs/XR91.pdf12:43
DocScrutinizer05http://data.energizer.com/ is quite convenient site12:48
wpwrakAAAA ... heh, another exotic type :)12:54
wpwraki want to stay mainstream. the sort of batteries you can find in a village you visit for the first time and where you don't speak the local language :)12:55
wpwraki.e., AA >> AA > CR2032. but then AA would be rather big.12:58
DocScrutinizer05go for AAA then12:59
DocScrutinizer05even CR2032 are sort of tricky12:59
DocScrutinizer05and friggin expensive13:00
wpwrakaround here they're about 50 us-cents apiece if you buy a bunch. else, about 80 us-cents. so they must be single-digit cents in the rest of the world :)13:01
paul_boddieArgentina provides the "distressed economy" test, I guess. ;-)13:20
wpwrakguess that's happens when beavis and butthead grow up and become ministers13:25
paul_boddieWonder how much they are here... 29 NOK!13:28
paul_boddieI was reading about Argentine political history not that long ago. Enlightening and rather sad.13:29
wpwrakelections are in october. there will be a reckoning.13:29
wpwrakNOK 29 = USD 3.6. that's for how many CR2032 ?13:30
paul_boddieJust one at expensive retailer: http://www.clasohlson.com/no/Varta-litium-batterier/32-223613:31
paul_boddieTheir UK shop is as expensive. Will look closer when next in the supermarket.13:33
wpwrakwow, nice margin ;-)13:33
wpwrakfirst hit on ebay: http://www.ebay.com/itm/5-Energizer-2032-Battery-CR2032-Lithium-3v-Batteries-/28063921859613:34
wpwrakfor really good prices, you may want to get 100 or so. like this: http://articulo.mercadolibre.com.ar/MLA-545118517-100-pilas-cr2032-sony-litio-boton-20blister-x5und-en-caja-_JM13:35
wpwrakthat's ARS 500, so about 50-60 US-cents13:36
paul_boddieThe amusing thing about Clas Ohlson's "own brand" cells is that there's a review by some Swedish person...13:37
paul_boddie...complaining that they used one in their banking code generator and it immediately complained about a low battery. Caveat emptor!13:38
wpwrakwell, if someone is gullible enough to pay at that price, ...13:38
wpwrakhmm. s/pay/buy/ || s/ at//13:39
paul_boddieThe cheap ones seem to work in kitchen scales and such things OK, in my experience.13:40
wpwrakif you want cheap and don't mind if it's alkalines and not button cells, how about this lovely deal ? http://www.ebay.com/itm/100-AAA-ALKALINE-LOOSE-BATTERIES-/121560854139?pt=LH_DefaultDomain_3&hash=item1c4d976e7b13:40
wpwraksomebody must have been robbing the trash bins13:41
larsc'these have been in our warehouse for a few years and the boxes got water damaged'13:42
paul_boddieOf course, corroding coin cells are a real peril with old computers.13:43
wpwraknever saw a coin cell corrode. alkaline, though, armies of them ...13:47
paul_boddielarsc: Looking at the jz4740 PWM driver, it appears usable for the jz4730 at a glance, but I think the pin assignments differ.13:56
larscyea, that's kind of expected13:57
larsclet me have a quick look at the datasheet13:58
paul_boddiewpwrak: http://www.retro-kit.co.uk/page.cfm/content/Acorn-BBC-A3000-Battery-Maintenance/13:59
pcercueithat's not a problem13:59
paul_boddiewpwrak: Although that's technically not a coin cell.13:59
pcercueithe PWM driver doesn't know anything about the pin assignment13:59
paul_boddiejz4740_pwm_gpio_list mentions JZ_GPIO_PWM0 through JZ_GPIO_PWM714:00
paul_boddieJZ_GPIO_PORTD(23) through JZ_GPIO_PORTD(31), apparently.14:00
pcercueibecause that's old code14:01
pcercueiwe have an updated one: https://github.com/gcwnow/linux/blob/jz-3.19/drivers/pwm/pwm-jz4740.c14:01
paul_boddieIs that going to be merged upstream at some point?14:01
pcercueithat's the plan14:02
pcercueibut I need larsc to finish the pinctrl driver first :)14:02
pcercuei(since this updated driver requires that you have a pinctrl driver)14:02
paul_boddieLinux dependency hell! ;-)14:03
paul_boddieIs it worth following device tree work for jz47xx? If so, where should I be following?15:29
larscnon-devicetree is not going to be supported in the future15:30
paul_boddieI see that there's some jz4770 DT stuff, and maybe the MIPS people did some jz4780 DT stuff as well.15:34
whitequarkwpwrak: that's because coin cells use methanol for electrolyte15:36
whitequarkthey're not really "battery" cells15:36
whitequarkthey're more like fuel cells with a semipermeable membrane15:36
whitequarkand metallic li15:36
pcercueithere's some jz4740 stuff as well15:47
paul_boddieI found a 3.18 branch in gcwnow for DT, but is that the "most upstream" place?15:54
pcercueiqi-hardware is the "most upstream" for jz4740, gcwnow is the "most upstream" for jz4770, MIPS/CI20_Linux is the "most upstream" for jz4780 :)15:55
paul_boddieI meant for DT. I didn't think the qi-kernel repo was being updated any more.15:56
pcercueiah, then it's the jz4780 tree from the MIPS guys15:57
pcercueiwe started moving our jz4770 tree to DT some months ago, but some parts (e.g. clocks driver) aren't easy15:57
paul_boddieOK. I'll have a look at what the MIPS people have for DT.15:58
paul_boddieShort of that, I'm tempted to do some dirty hacks to see if the "old" jz4740 PWM driver can be tweaked to work with jz4730 pin assignments.15:58
paul_boddieI think the timer/counter registers are the same between the jz4730 and jz4740.15:59
pcercueiif you want to do it cleanly, bump larsc - IIRC he has a pinctrl driver ready for jz474015:59
pcercueithe pin assignments are done in DT so it would probably work on jz4730 as well16:00
pcercuei(e.g. we use the exact same pinctrl driver for jz4770 and jz4780 now)16:00
pcercueiif the subsystem didn't change too much it may even be used for older versions16:00
paul_boddieI think the confusing thing when looking at the old (2.6) code is, apart from kernel coding changes, the way some things like PWM are done.16:04
paul_boddieIt's hard to tell from vendor code, though, as they dump their internal knowledge to C.16:05
paul_boddieBut since the timer/counter unit looks the same, we can probably ignore weird vendor stuff and go the tried and tested route.16:06
eintopfwpwrak: that's like the shaver which buys blades when they are empty17:15
paul_boddieeintopf: Hope it has built-in "surge protection" for when someone's child presses the button for chocolate a hundred times. :-)17:49
arossdotmewhat is the resistor value to put across a usb socket to that connects to a usb charger to get max current?18:30
arossdotmei'm making up a micro usb socket pwr input adaptor for my zipit.18:31
arossdotmeso i can use a standard microusb socket to charge/pwr my device18:31
arossdotmewhere would i find this info, in the usb doc? isn't such info hard to find in the doc?18:32
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