Hi I need an explanation on arduino leonardo schematic.. - Page 1
Forum section: electronics / projects

author: shailee
author_rank: Newbie
timestamp: April 09, 2013, 10:33:20 am
content: HiI need an explanation on arduino leonardo schematic.I need to understand every single thing in the schematic.Write to me whatever you know, anything will help me..Please help me..

author: dr_p
author_rank: Frequent Contributor
timestamp: April 09, 2013, 11:16:57 am
content: Since you seem not to know anything in the schematic, you shouldn't be playing with micro-controllers in the first place, should you?http://bit.ly/10OfaXRor (convince parents to) buy an electronics beginner game, or a book, or follow tutorials on youtube, google, books, local groups, come on...Who do you think has the time to answer the questions that you did not bother to ask?We will help, but make the first move. Learn some stuff for yourself instead of saying "pretty please, explain everything to me." And there's alot going on in that schematic, from a noob's perspective.Build something, and I mean simple stuff, an LED, a resistor and a battery. Verify Ohm's law, learn to use a capacitor, a diode, a transistor. Build simple 1-2 transistor circuits.Visit the local electronics shop for kits or order them online, try to get ones that you'll actually use when completed.I love to see people interested in electronics, but I totally dislike Arduino as a first step in doing that. Yes, you might accomplish the goal, but you have no idea why, how, or what to do if it's not working. If you don't have basic EE knowledge you don't stand a chance at figuring it out.So do yourself a favor and if you really mean it, take some time and study. The internet is full of good material and it's very easy to find it.

author: psycho0815
author_rank: Regular Contributor
timestamp: April 09, 2013, 12:47:31 pm
content: Have a look at the atmega32U4 Datasheet. Most of what's in the schematic comes more or less straight from there. Apart from that it's just a couple LEDs, lots of decoupling caps and a opamp comparator to switch between power sources. Have a look at any basic opamp tutorial. it shouldn't be to hard to figure out how it works.As for the general Arduino discussion: It's propably not the best tool to actually learn how µCs work. As soon as you outgrow the Libraries you're gonna have to dive into avr-libc stuff anyway, so you might as well start there. It also enables you to use much cheaper controllers for most projects. ( Yeah i know you can use the Arduino tools with attinys, but it can be quite the pain in the butt).But then, off course some people just want to make something blink, display temperature or whatever and don't really give a crap about how it works.And that's fine too.

author: airiclenz
author_rank: Contributor
timestamp: April 09, 2013, 01:26:38 pm
content: Hello shailee,can you tell us what you do understand and what not? Explaining something without knowing the context / background of the person that receives the explanation is pretty hard. It would be nice to have a starting point.And if you don't know anything, then dr_p is right.Airic

author: shailee
author_rank: Newbie
timestamp: April 09, 2013, 01:31:23 pm
content: sorry I'll explain myself..I am studying electronics in college and I do a final project.In my project I use arduino leonardo.I need to know the internal structure, (all of entry and exit, how USB works, the reset batton, etc.)Because i will be examined for it.

author: psycho0815
author_rank: Regular Contributor
timestamp: April 09, 2013, 01:39:33 pm
content: As i said the datasheet, will explain all the specifics, like the usb stuff, reset, and AVCC circuitry. The rest should be fairly obvious for an electronics student.

author: airiclenz
author_rank: Contributor
timestamp: April 09, 2013, 01:45:34 pm
content: Ok, that's a start.Try reading the documentation of the used Atmel chip (ATmeag32U4) . This should explain quite a lot (everything is basically included there: Inputs, Outputs, USB, Reset, ...). All the other stuff on the Leonardo is just support for this chip which makes all this integrated functionality accessable (power supply, header, fuses, ...). Try also reading the other datasheets for the parts used on the board. You'll find the names of the parts in the schematic and a Google help will give you the corresponding PDFs.After you unsderstood the hardware, I suggest looking at the software side too because this is a major point for the hole Arduino infrastructure!When suggesting this I guess you have a basic understanding of electronics (voltage, current, resitors, pull-ups/downs, capacitors, transistors and all that stuff).Airic

author: shailee
author_rank: Newbie
timestamp: April 09, 2013, 01:50:27 pm
content: The atmega32U4 Datasheet I understand.I need to understand in the schematic all the other things..What is the role of each capacitor, diode, amplifier etc'..

author: electronupdate
author_rank: Regular Contributor
timestamp: April 09, 2013, 02:04:21 pm
content: U1 and U2 are micro controllers made by Atmel. You will want to read the whole data sheet on those... they are fairly complex.U1 is used as a USB to serial converter.U2 is the "actual" micro controller that runs user code.This is historic. Most personal computers had a serial port and lots of controllers could talk directly to them. A serial port is an inexpensive peripheral to put onto silicon and is one of the most simple ways of providing debug access to a micro controllers. As time went on most computers dropped the serial port and adopted USB... thus the need for U1 as a translator. I believe the 1st version of the arduino were serial only.C3, C4, Y1, R1 form part of a "crystal oscillator"... you will want to google that term. Inside U1 will be an amplifier... These components provide the fundamental timing source for all actions of both micro controllers.T542 and RN1D (4-5) provide a reset button. when it's pressed the input pin is driven low which resets the mico controller. when released the pull up resistor (RN1D) puts the pin to a voltage near 5V (i.e. logical one).C1 and C2 are "decoupling capacitors"... you will want to google that term to learn more about what they doIC2A is an op-amp in a non-inverting configuration. Vout = Vin... sounds useless except that it does "impedance conversion". The driver going into pin 3 (IO13) is "weak" (unable to drive significant current). The op amp has a "stronger" driver that allows it to drive the LED. There is some smart engineering going on here... normally it would be a waste of money to use an op amp to drive an LED... however the designer put on a dual (two op amps in a single package) and used one for an LED and the other for a purpose which required an op amp. If only LED driving was required a simple transistor would have been cheaper... however here there was a recognition that if a dual-op amp was used it would be cheaper than putting down two different parts (a single op amp and a transistor). This topic often comes up in industrial engineering on building cost effective design.J1 is the USB connector. Z1 and Z4 are "ESD protection". you will want to google that term. ESD protection is good engineering when a person can touch a connector.... in a real application a user may carry a significant electrical charge and you don't want the product destroyed when they insert a cable.I believe IC2B is the power supply select. This board can be powered either directly through the USB cable (from power from the computer) or from an external adaptor. the op amp is being used as a comparator.IC1 and U3 should be "linear voltage regulators". google that. also google the part numbers to make sure that's what these are.D1 is more smart engineering. if a customer puts on a power supply backwards the diode will conduct preventing further damage to the board (d1 + a fuse might be even better).Quote from: shailee on April 09, 2013, 10:33:20 am

author: smashedProton
author_rank: Frequent Contributor
timestamp: April 09, 2013, 02:38:53 pm
content: For circuit analysis, you have picked a pretty ccrappy circuit to analyze. Its just gpio and a usb interface. I would look at a more in depth digital design

author: free_electron
author_rank: Super Contributor
timestamp: April 09, 2013, 03:30:42 pm
content: Someone wants us to do the work to get him the passing grade.....It all works on smoke... Because if the smoke comes out it's broken...

author: smashedProton
author_rank: Frequent Contributor
timestamp: April 09, 2013, 03:45:26 pm
content: +1. My cat can underst and that schematic. If you want to be a successful electrical engineer, you need to be passionate for the subject. If you don't understand that schematic, I doubt that you can turn an led on or off. Which brings uo the question of why you are studying ee

author: RedGrittyBrick
author_rank: Newbie
timestamp: April 09, 2013, 08:24:18 pm
content: Hi Shailee,I notice you also posted this rather broad question to the arduino.cc forums (and I guess to other places). I suggest you stick to asking one place and only ask elsewhere if you don't get any helpful replies in a day or so.It may be more productive if you can start by identify just one part of the schematic you don't understand and explain what research (if any) you've done to find out and what you have found out so far. Indicating your level of knowledge always helps otherwise people don't know if they have to start by explaining at a beginner level.Good luck.