#avr Logs

Oct 25 2020

12:30 AM day_ is now known as day
02:16 PM joakimk: I'm going to power an ATMEGA88 on a breadboard (been running it thus far within the STK500). Regarding power supply; can I do without a voltage regulator (LM7803) if I find a 5V rated power supply? Or should I *always* have a regulator, no matter what?
02:17 PM joakimk: With a 5V "wall wart", can I simply do with some capacitor on the supply, to "even out" the supply from the power supply?
02:17 PM joakimk: ^ even out the voltage, I mean (or is it even out the current?)
02:18 PM joakimk: I've had problems using a 5V supply "directly" previously. A friend helped me out, and I think he simply added a capacitor on the VCC
04:10 PM rue_mohr: if its a regulated 5V supply, lieka usb adapter, your fine
04:10 PM rue_mohr: some of the dc adapters (the old magnetic ones mostly) are "about 5V when loaded to the rated current"
04:11 PM rue_mohr: which means they might put out 15V under no load
04:15 PM Igloo: You might get odd behaviour if you don't put a 100nF capacitor across the power rails with USB power, though, though
04:21 PM joakimk: So a phone charger (USB plug) is a good choice for a wall-powered AVR?
04:21 PM joakimk: Igloo: Does that mean 100nF between VCC and GND (from the USB)?
04:22 PM joakimk: rue_mohr Thanks for the caution... I'd have thought if it said "5V 500mA" (for instance) on the plug, then that's what I could expect ;)
04:22 PM joakimk: but you're saying, you can only expect 5V if you actually load/pull 500mA?
04:30 PM joakimk: Igloo: When you say 100nF, can it just as well be 150nF? I just can't seem to find any 100nF caps among my stuff...
04:32 PM joakimk: So the question is, how "precise" are those cap ratings? I see various schematics for hooking up the LM7805, and it tends to specify 0.33nF and 100nF. If I use that regulator, will I *have* to get those caps just right? How big is the leeway
04:32 PM joakimk: Still, using a USB phone socket/charger (with a cap) does sound extremely convenient :)
04:37 PM Igloo: Between VCC and GND, yes. I'm sure 150nF will also be fine.
05:36 PM rue_mohr: almost all the new ones are regulated
05:36 PM rue_mohr: avrs are also extremely noise-tolerant, if it were a PIC, you would have to be REALLY carefull with the power or it would lock up continiously
05:37 PM rue_mohr: which is one of the reasons I abandoned PICs, they dont reset properly on brownout
05:37 PM Igloo: I've had problems, although that might have only been when running off of an old laptop's USB port
05:38 PM Igloo: I really really want to use a PIC for USB support in a small DIP package, but I'm dithering because the open source support for them looks so much weaker
08:59 PM Rab: If it helps, I believe it's technically not possible for a DIP package to comply with the USB spec. (Although there are many mass-market USB peripherals with DIP controllers, e.g. cheap mice and keyboards.)
09:20 PM Igloo: Huh, why is that?
09:52 PM Rab: Igloo, the physical pin geometry (spacing etc) is not suitable for the ideal USB signal pair.
09:53 PM Rab: But I mean, obviously there's tons of hardware that runs USB over 0.1" pin headers etc.
09:54 PM Rab: So at the USB 1.1 speeds you'll get from an AVR, it's probably fine.
09:56 PM Rab: Er, I mean PIC in DIP. The AVR V-USB junk violates the spec in other ways as well. And the real USB AVRs aren't in DIP.
10:22 PM Ameisen: I have a 10.2.0 build of AVR-GCC locally
11:16 PM funky is now known as Streaker