#avr Logs

May 14 2020

09:24 AM sergche1991: I can neither talk via uart nor burn a firmware via isp when avr is powered by ~3.85v lipo battery. Shouldn't that voltage be enough to produce a guaranteed logical 1? Or do I need to make a level shifter?
09:34 AM LeoNerd: Yah this is sounding a somewhat confused question. I run AVRs on 3.3V all the time and they work fine.
09:34 AM LeoNerd: Lets start from the beginning and explain what you've got
09:37 AM sergche1991: Mega328. Powered with a lipo battery with ~3.85v. No voltage regulators, so vcc is equal to battery's. It works fine, except problems with communication to stk500 and usb-ttl.
09:38 AM sergche1991: stk500 can initialize an avr device, but gets wrong or blank device ID. usbttl adapter can't get even any noise.
09:38 AM sergche1991: When I power mega with 5V both work.
09:40 AM LeoNerd: Ooh.. STK500. Yeah that probably has quite strict voltage requirements
09:48 AM rue_mohr: iirc the dragon was that one that blew up all the time from not being attached without buffering circuits
10:06 AM skz81: sergche1991, do you know i your circuit runs at all with 3.85 V ?
10:10 AM skz81: as per chapter 29.3 Speed Grades, 3V85 is safe until ~16Mhz (may have done the math wrong though)
10:11 AM rue_mohr: sergche1991, run the avr on a regulated power supply of 3.3V or 5V when programming
10:16 AM twnqx: sergche1991, and in particular the voltage your programmer is meant for (unless you have level shifters)
10:19 AM skz81: Hu I just got the actual question / problem :)
11:47 AM Rez__ is now known as L
11:20 PM day_ is now known as day