#qi-hardware IRC log for Tuesday, 2012-02-07

rjeffriesBRCM publishes a datasheet for the chip in Raspberry Pi http://www.raspberrypi.org/archives/61501:02
wpwrakthat's pretty good indeed01:05
rjeffrieswpwrak I look forward to learning if the datasheet comes anywhere close to meeting your standards. I have not read the whole thing, I thought the SPI, I2C and UART parts looked pretty good01:22
wpwraki had a quick look at it. it does look useful for programming. not sure it it contains all the information you need (sometimes you only find out something crucial is missing when you actually try to do something), but it looks quite promising01:24
kristianpaulnice, from the Pi guys02:00
wolfspraulkristianpaul: what?02:01
kristianpaul20:02 < rjeffries> BRCM publishes a datasheet for the chip in Raspberry Pi http://www.raspberrypi.org/archives/61502:01
kristianpaulafaik and i guess as spected i dont read too much info about video02:02
wolfspraulabbreviated datasheet :-)02:02
kristianpaulindeed !02:02
wolfspraulhey, at Milkymist we have the entire source of the entire chip02:03
wolfspraulhow about that :-)02:03
kristianpaulhard to beat :)02:03
wolfspraulbut I do like the Pi project, nonetheless. I just hope they push our real boards and keep them cheap and shuffle a lot of great software on their boards. power to people...02:04
wolfspraulpush out02:04
kristianpaulI _just_ like the price, but i hold my hopes, but smell another OLPC-like "cheap" computer project 02:05
kristianpaulwe'll see02:05
kristianpaulmay be not02:05
wolfspraulI had another question about DocScrutinizer's idea a while back with the aluminum stripes on the bottom side of the Milkymist One PCB...02:05
wolfspraulunfortunately he may be sleeping already and mine and his timezones don't overlap well now, urgh ;-)02:05
wolfspraulquestion was about whether it had to be aluminum, or what the difference to a copper strip would be02:06
wolfspraulalso the width, whether thicker would do as well02:06
wolfsprauland finally whether it would matter if the glue was conductive as well02:06
kristianpaulthe X shaped aluminum thing? or was that tape?02:06
kristianpaulsoem kind of tape*02:06
wolfspraulI just looked a hundreds of different conductive tapes recently and got a little shock that I had no clue which one might actually follow Joerg's idea :-)02:06
kristianpaulah :-)02:07
wolfspraulyes, tape02:07
wolfspraula big X on the bottom side of the pcb so we can remove the metal shield and still achieve the same EMI effect02:07
wolfspraulno, sorry. ESD02:07
wolfspraulso the questions are: wider ok? 1cm, 2cm? copper? conductive glue?02:07
wolfspraulkristianpaul: well, I personally wouldn't spend time on the Pi project because I think Milkymist is so much better, cooler, more interesting and promising02:08
wolfspraulbut the great thing about Pi (*if* they make it there which they have not yet), is that it may offer cheap boards today02:08
kristianpauloh no me either02:08
wolfspraulemphasis on *today*02:08
wolfspraulit's about speed and price02:09
kristianpaulas i had said, price is one thing call me atention for running a cheap webserver02:09
wolfspraulso it may be able to solve some problems today that Milkymist in all its coolness and promise cannot solve today02:09
rjeffrieswolfspraul I understand totally. a differnt view is that a decent platform for $50USD that runs Linux can be used by many people ho can not afford MM and also it is arguably a more general computer platform02:09
kristianpaultought i can do that with milkymist, just no plans to order one 499usd webserve yet ;-)02:10
kristianpaulbut i was trying rtems httpd other time02:10
kristianpaulwas quite nice for my requiremns of running html plain webpages ;D02:10
rjeffriesone supposedly can order Raspberry Pi for delivery early March02:10
wolfspraulwe get the price down, but not now and not to catch up/compete with Broadcom, but instead to just make Milkymist more attractive and affordable for more people...02:11
kristianpaulyes sure thats cool02:11
rjeffriesthese two things do not compete02:11
rjeffriesone sells in qty of 100's the other will be in qty of 10K and far greater02:12
kristianpaulethernet have its potencial, also *theorically* fpga acelerated webserver etc02:12
rjeffriesmay 1,000 flowers bloom02:12
rjeffriesnobody has to buy one or the other.02:12
kristianpaulactually i had read some interest of moving fpga's to the servers fields.02:12
kristianpaulmay be roh now more about it?02:12
kristianpaulanway.. lets try be usefull for 2 hrs :-)02:13
Action: kristianpaul away of irssi02:13
wpwraki think making the X wide doesn't matter02:55
wpwrakconducting glue sounds dangerous, though. you don't want to short contacts/components at the bottom of the pcb02:56
wpwrakalso, copper should be even better than Al. probably also more expensive02:57
wolfspraulthere are quite a few parts on the bottom side03:02
wolfspraulso we cannot rely on just hoping that the glue will insulate 'enough'03:03
wolfspraulthe conductive properties of the glue are quite important then03:03
wolfspraulsay if you push the strip down, you may push the metal layer against the parts...03:03
wpwrakyup. that's probably something that needs considering03:04
wpwrakunless the tape has its own fairly solid isolating layer03:04
wolfspraulwell, when I saw those hundreds of tapes I knew I didn't know enough for sure ;-)03:04
wolfsprauloh I bet that exists, we just need to be clear03:04
wolfspraulso maybe we need a 3-layer tape, first copper or aluminum, the insulation, then glue03:05
wolfspraulor a glue that is *really* insulating, even when the tape is glued over and pushed down onto small and sharp smd parts03:05
wpwrakhmm ...03:05
wolfsprauldoesn't sound very convincing ;-)03:05
wolfspraul3-layer probably...03:05
wolfspraulthe tape has to have some insulation already03:06
wpwrakmost tapes have some sort of foam at the bottom. so that foam would have to be thicker than the tallest elevation03:06
wpwrakplus, when you compress it, e.g., when putting the tape, it must extend again03:06
wolfspraulyou mean it must be impossible for any part to protrude through the foam?03:06
wpwrakand that's not even talking about compressing it with the case off ;-)03:06
wolfspraullike I said, it sounds like we need a strong insulation layer under the copper/aluminum03:07
wolfsprauljust hoping the glue is enough won't do03:07
wpwrakyes, that sounds good03:07
wpwrakif you can't find that, maybe some separate isolating sheet and then the conductive tape on top03:08
wolfspraulI'm sure we are not the first ones with this requirement, so it comes down to finding the right tape03:08
wolfspraul3M seems to have a lot of tapes03:08
wpwraka separate sheet would also make it easier to see damage03:08
wpwraki think that's an understatement ;-))03:08
DocScrutinizer51wait what? you're now planning to stick the shielding (X) *to the PCBA*??07:33
DocScrutinizer51that's for sure not what I suggested07:33
DocScrutinizerthis definitely won't work for the intended purpose07:53
DocScrutinizerI suggested to stick the X to the plastic plate of the case, not to the PCB07:54
DocScrutinizerwe talked about this to gory detail, about using conducting posts to connect to the (protective) GND of the PCB via the mounting holes for the posts07:56
DocScrutinizerabout no concerns that glue does NOT conduct as we can connect each bar of the X separately so the X has no need to connect in the center where the bars cross each other07:57
DocScrutinizerIIRC you complained that it's much manual work to cut that metal sheet to shape, and I suggested to use sticky tape *instead*08:00
DocScrutinizerbtw IIRC I also suggested you could use aluminium varnish spray and coat the inside of your plastic case plate08:01
DocScrutinizerand you for sure won't need to isolate any of the tape or varnish against the plastic08:02
DocScrutinizerand depending on mechanical rigidness of both the PCB and the case plastic plate (with attached conductive shield) you may omit the isolation sheet between the both08:03
DocScrutinizerwhen there's like 10mm distance from highest capacitors or whatever on PCB down to the bottom plate of the case with the shield, then the air should isolate enough and no way case or PCB would bend so they touch each other08:05
DocScrutinizero/ daywork08:05
wolfspraulDocScrutinizer - ok cool, read your response - thanks!11:13
wolfspraulthe first misunderstanding was that you mean to glue the tape on the inside of the bottom acrylic11:13
wolfspraulthat will not be 10mm from the capacitors, maybe only 3-5 or so11:13
wolfsprauland as far as the pcb touching on the tape, why not just take a tape where the top side is insulated? that would prevent that for sure11:15
wolfspraulso it's 3-layer - glue, then aluminum/copper, then insulation11:15
wolfspraulglue that in a large X onto the inside of the acrylic bottom panel, connecting only on one side of the 2 strips11:16
DocScrutinizer51you also want to have  tape on edges11:37
DocScrutinizer51so a rectangle with an X inside11:37
DocScrutinizer51unless your acrylic s already in a metalframe11:38
DocScrutinizer51-15 here. cig at work11:39
DocScrutinizer51outside :-/11:39
larsccybernetic implant growth11:45
larscand apparently those start to fail start to fail at -15C11:50
viricit's a matter of changing the antifreeze, simply11:52
lindi-it's 20 degrees warmer here than last week:  http://outside.hut.fi/month.html11:55
wolfspraulok, rectangle as well :-)12:19
wolfspraulthe rectangle will connect all 4 edges electrically, I assume12:19
wolfspraulbut the X will only connect on one side of the 2 strips? guess so (that's what was said before)12:20
wolfspraulagain: thanks!12:20
wolfspraulin case anyone is interested in IC production costs, I ran into this nice overview with prices http://cmp.imag.fr/products/ic/?p=prices12:25
Action: pabs3 mentioned Qi on https://lwn.net/Articles/479371/12:50
wolfspraulpabs3: nice, thanks for remembering Qi ;-)12:52
whitequarkwhoever here was doubtful about osPI15:08
whitequarkrue, IIRC15:08
larscwas ist15:08
larscwas  it15:08
rohah. nice to see17:35
rohhm.. just need to find a machine to view em on17:35
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