#avr Logs

Nov 25 2018

03:48 AM eszett_: hi.
03:52 AM eszett_: decoupl. caps are mandatory close to each power pin. However I'm scratching my head about this https://i.imgur.com/qELDw50.png the trace betw. pin2 and C1 is not much shorter than betw. pin2 and C5. So C2 is pretty unncessary as decoupl. cap, isnt it?
04:14 AM rue_bed: eszett_, still there?
04:15 AM eszett_: ye
04:15 AM rue_bed: ok, I'll actaully look then!
04:16 AM rue_bed: often the caps are on the other side, under the chip, but thats fine
04:16 AM eszett_: so do you think one cap can be deleted?
04:16 AM rue_bed: yup
04:17 AM rue_bed: avr's aren't pics
04:17 AM eszett_: cool..
04:17 AM rue_bed: they are really noise resistant
04:17 AM rue_bed: are you using the adc?
04:18 AM eszett_: not at all.. it's just a keyboard PCB
04:18 AM rue_bed: k
04:18 AM eszett_: There is another thing which I have to ask. The datasheet says it's recommended to have a 10µF cap on the "VBUS line", but there are two pins called like that. on the USB receptacle, and on the Atmega. Which VBUS is meant here?
04:19 AM eszett_: I guess the USB connector's power line, not the Atmegas VBUS pin?
04:19 AM rue_bed: hmm, I'v not dealt with the u4
04:19 AM rue_bed: tom has but he's not awake
04:19 AM eszett_: ok..
04:19 AM rue_bed: why does the avr have a vbus pin!?
04:20 AM eszett_: it seems to be a VBUS monitor pin.
04:20 AM rue_bed: then they should go togethor....
04:20 AM eszett_: So the name "VBUS" is irritating at least.
04:20 AM rue_bed: odd, cause vbus will often be over spec for 5V
04:21 AM eszett_: ye
04:21 AM vmt: --
04:23 AM eszett_: I'm asking because decoupling caps have to be close to the power pins. However, the 10µF seems to be an inrush cap, which doesn't have to be close to a pin as the other decoupling caps. And Atmel means the "VBUS" pin on the receptacle, therefore synonymous for all the power lines as a whole?
02:05 PM guanche: hi, has anybody ever done high voltage programming? I'm looking at this: https://microtherion.github.io/ScratchMonkey/HVPP.html
02:06 PM guanche: and it says the target mcu is powered (5V VCC) through the SVCC pin, but I can't find any info on it (I've never used an arduino), or is it just that the target mcu is powered by some gpio pin of the programmer's mcu?
02:42 PM twnqx: guanche: iirc HVP is "just" assigning 12V to the RESET pin
02:43 PM twnqx: everything else should be as always
02:48 PM guanche: it says on the datasheet vcc to the target should be timely controlled, I will use some bc transitor for it twnqx
02:49 PM twnqx: i think the only time used HVP was with an STK500, so i relied on atmel to get things right ;)
02:49 PM guanche: hehe, I don't have any of that either, but it will be fun trying to get it working
03:23 PM [1]MrMobius is now known as MrMobius
06:05 PM Arch-TK is now known as atk
09:00 PM LeoNerd: cehteh: I've got another 6 of those boards now with new silkscreen markings for 14.7 and 18.4 - let me know if you'll be wanting me to build them up for you
09:18 PM [1]MrMobius is now known as MrMobius
11:43 PM day__ is now known as day