#avr Logs

Apr 29 2018

02:41 AM polprog: morning
03:25 AM Emil: moorming
06:55 AM * nuxil sips some coffee
06:55 AM Emil: uuh
06:56 AM nuxil: whats up
06:56 AM nuxil: makeing anything cool?
06:56 AM Emil: 1 hour until doors open and 1.5h until fuksispeksit starts
06:56 AM nuxil: whats that ?
06:57 AM Emil: https://oubs.fi/live/
06:57 AM Emil: https://www.youtube.com/watch?v=eMEqY_0AeRc
06:57 AM Emil: https://wappu.fi/event?id=110&lang=fi
06:57 AM Emil: (Last link has event info in both Swedish and English also)
07:02 AM nuxil: oki
08:28 AM polprog: Emil: sounds cool
08:28 AM polprog: guess what i bought today
08:28 AM polprog: and for how much
08:30 AM antto: a pepsi for 1 euro?
08:31 AM polprog: a ti 83 plus for 30 pln
08:31 AM antto: a wat
08:32 AM polprog: a texas instruments calculator
08:32 AM antto: don't you have a comput0r?
08:32 AM polprog: for $8
08:32 AM polprog: oh i have a lot of computers :p
08:32 AM antto: i have a calculator in mah phone even
08:34 AM polprog: i even have a ti-89 emulator on my phone
08:42 AM nuxil: nice
09:06 AM nuxil: This is what i been doing https://gyazo.com/7cff9402880a30cf329612578392f9c4 . Finnaly got the spaghetti nest "sorting" out" today..
09:06 AM nuxil: Now the printer also lightup red as hot https://gyazo.com/0afd886a8ded40ff70a1ea9c203626bb and blue as cold https://gyazo.com/2d17b351fd8c2077fbfbc7627914029a :)
09:07 AM nuxil: the tevo tarantula should be renamed to spaghetti troll. just look at how it looks like when following the manual https://all3dp.com/app/uploads/2017/12/tevo-tarantula-hero-1032x580.jpg :p
09:07 AM nuxil: wires everywhere :p
09:08 AM nuxil: still a few tings left tho. like mount the guy wires and a few other things
09:31 AM nux_ is now known as nuxil
10:06 AM polprog: nuxil: pimp my printer
10:06 AM polprog: :p
10:08 AM antto: print my pimper
10:17 AM nuxil: polprog, yeah :D
12:53 PM day__ is now known as day
02:28 PM lvlinux: Hey guys i have a question: I'm needing a smooth, programmable ramp voltage (sawtooth wave), and I need to be able to set the start and end voltages to within around a mV, and change the speed (between about 1 and 20Hz or so.) Should I use an external DAC, or would I be able to accomplish that reliably with an AVR with PWM or something, and still have accurate control, and a perfect straight line ramp (with
02:28 PM lvlinux: proper filtering)?
02:29 PM lvlinux: Most circuits I see do this with a 555 timer and several op amps, and pots. I thought about doing that and using the arduino to control some digital pots, but if it could be done more directly it would be better.
02:31 PM lvlinux: excuse me, I mean AVR, not arduino lol...
02:37 PM polprog: whether you can use PWM depens mostly on the frequency
02:37 PM polprog: you want your sawtooth output to be
02:37 PM polprog: are you driving some kind of a CRT?
02:42 PM Casper: lvlinux: high speed PWM might work, and if you have lots of pins on your avr you could maybe go with a R2R DAC
03:00 PM polprog: sorry i didnt read
03:01 PM polprog: 1 to 20 Hz should be easily doable with a proper filter on the output with PWM
03:01 PM polprog: no problem there
03:01 PM lvlinux: It's for control of a VCO for use in a spectrum analyzer.
03:01 PM lvlinux: So you think PWM would give me at least the accuracy that I need? (1mV)
03:02 PM Casper: fastest PWM possible, heavy duty filtering
03:02 PM lvlinux: I have several 12 bit DACs if that would be more "correct".
03:02 PM polprog: what casper said
03:02 PM Casper: what voltage range?
03:02 PM polprog: if you ave good dacs why do you even bother?
03:03 PM polprog: instead of doing heavy filtering (i assume it has to be super correct) just use those dacs. less hassle
03:03 PM Casper: 0-5V? 5/65536 = sub 1mV technically.
03:03 PM polprog: 76 uV
03:04 PM Casper: R2R 13 bits would give the precision, and basically no filtering needed
03:04 PM Casper: but that one also require 13 pins
03:05 PM polprog: 12 bit dac gives 1.22 mV so thats a bit over the top
03:05 PM polprog: theoretically PWM would give better accuracy
03:06 PM Casper: I'm actually worried about the ripples and how hard it can be to proprelly filter them while keeping the raise/fall time
03:06 PM Casper: the pwm on avr is slowish
03:07 PM polprog: 20 hz is really slow. id give it a try
03:07 PM polprog: on the other hand ripple on PWM is terrible,
03:07 PM Casper: that is why I suggest R2R if there is enought pins available
03:08 PM lvlinux: that's what i was concerned about. The actual voltage range I need is 1-16 or 18V though, and I can run the DAC at 18V.
03:09 PM lvlinux: Would ripple be any different with 1Hz vs 20Hz with PWM?
03:10 PM lvlinux: So I guess it sounds like the DAC is going to be the best solution. Will still need some filtering though I guess.
03:10 PM polprog: yeah
03:10 PM polprog: by the way, what DAC? i want to get one or two to mess around
03:11 PM lvlinux: I have several old ones, mostly Burr Brown DAC80 and DAC85.
03:11 PM lvlinux: I've never used one but thought this project might be suitable to start.
03:13 PM lvlinux: They're parallel input but I might use an i2c expander or shift register to get around that if i end up needing other pins for other stuff.
03:14 PM Casper: clock speed / TOP = pwm frequency, now do the filter math with the raise/fall time of your filter
03:16 PM lvlinux: k
03:16 PM lvlinux: I guess i need to do some experiments with PWM anyway to get more familiar with it.
03:17 PM lvlinux: But I think I'll use a DAC in the spectrum analyzer.
03:17 PM Casper: if cost is not an issue, I'ld use a dac
03:17 PM Casper: consider to protect the dac with an opamp in front of it
03:17 PM lvlinux: I got the DACs I have for a penny each lol.
03:18 PM polprog: "in front"
03:18 PM polprog: you mean on the output :D
03:18 PM polprog: i keep thinking front === input
03:18 PM lvlinux: an op-amp to protect it? From what would I be protecting it?
03:18 PM polprog: :P
03:19 PM polprog: just a buffer, at this frequency should not cause issues
03:20 PM Casper: protecting it from short or whatever, if no risk then don't use it
03:29 PM lvlinux: k
03:29 PM lvlinux: won't hurt. Especially with these old chips, they may not have any sort of protection.
04:58 PM polprog: nigh
04:58 PM polprog: t
06:09 PM PsySc0rpi0n is now known as HelloShitty
09:27 PM Smashcat: Hi, anyone know of a software serial library that can work with an ATTiny44? (seems the one in the Arduino IDE doesn't work with this chip)
09:31 PM Tom_L: so why are you using arduino code anyway?
09:31 PM Tom_L: peter fleury has one
09:31 PM Smashcat: Tom_L: Was easier to transition from the ATMega code to ATTiny using the Arduino IDE. Everything is working except the softwareSerial lib
09:35 PM Tom_L: http://homepage.hispeed.ch/peterfleury/avr-software.html
09:37 PM Smashcat: Tom_L: Yes thanks, I took a look and that lib is using the hardware UART of some MCUs. The ATTiny44 doesn't have a hardware UART
11:42 PM day__ is now known as day