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1  Using Arduino / General Electronics / Re: MIDI thru circuit - problem with 74HC14 on: January 15, 2013, 10:35:51 am
Any possibility you are improperly inverting with that chip? Also, I wonder if there is confusion with pin 4 and 5 and which they really are.
Are 4 and 5 swapped on the input jack?
Both MIDI IN and OUT are connected properly. I checked it so many times. The circuit does work perfectly without 74HC14, so I am certain that the MIDI jack connections are good.

On a side note, why does every MIDI thru schematic include 74HC14 (or similar) if my circuit works good without it? Every single diagram I saw involved optoisolator (most often 6N138) and 74HC14? If my circuit works well without 74HC14 (6N138 straight to MIDI output), maybe there is no point in trying to include this element in circuit? I understand the need of optoisolator, but 74HC14 is a mystery for me.
2  Using Arduino / General Electronics / MIDI thru circuit - problem with 74HC14 on: January 14, 2013, 06:57:21 pm
Hello there,
I am building a MIDI thru circuit on my breadboard. I am using this schematic -
Unfortunately, it does not work. I am using exactly the same components as that guy. On the schematic it says 74LS14, but the topic title states 74HC14 so I guess I can use that. I've also tried this design (with 74HC14) - and it also doesn't work. I am using only one MIDI input and one output. I guess there is a problem with 74HC14 - when I omit it and connect my MIDI output (thru) pin 5 to pin 6 of 6N138 directly (without any connection to 74HC14) it works like a charm. When I connect pin 6 of 6N138 to pin 1 of 74HC14, pin 2 of 74HC14 to pin 3 of 74HC14 and pin 4 of 74HC14 to pin 5 of MIDI output (just like on the diagram) then it starts sending totally random messages (especially when I hold a battery in my hand). Sending message to MIDI IN port does not have any effect. Interestingly, when I tried that second circuit ( the LED worked perfectly and there was a co-relation between MIDI messages on the input and output. What I mean is that when I sent a message to MIDI IN, there was also a message on the MIDI OUT - but it was never the same message. It seemed to be a random message, but the timing was good.

It all leads me to think that there is a problem with my 74HC14 - because the circuit works good when I omit it (6N138 going straight to MIDI OUT). But again, when I was using the second diagram, the LED worked well, and also the timing of messages was good. So I don't know anymore... I have 5 units of 74HC14 (SN74HC14N) - all of them share the same problem. I power the whole circuit with 9V battery going through 5V regulator. I checked the voltage on the circuit and it's perfectly 5.00V. 74HC14 is powered by being connected to +5V (pin 14) and GND (pin 7).

Thank you for attention, I will be grateful for any clues.
3  Using Arduino / Displays / Re: Problem with some letters on LCD with LiquidCrystal on: November 11, 2011, 04:31:43 pm
Problem solved. I've just had an idea of putting 10k resistor on DB7 line and it worked. Thank you so much Don for pointing me that the problem is in DB7 line. Without you I would have never guessed it.

4  Using Arduino / Displays / Re: Problem with some letters on LCD with LiquidCrystal on: November 11, 2011, 04:20:59 pm
As far as your other problem goes - you appear to be having trouble with your LCD DB7 line (pin 14), it is always low.  This may be a problem with your soldering or with your breadboard.

I've changed that wire on DB7 to new wire and it's the same. I don't use breadbord for the screen, screen is connected directly to Arduino. I also tried to connect DB7 to different pin on Arduino (and change the pin number in code of course) but with no result. I also don't think that the problem is that DB7 is always low. When I connected DB7 to GND I also couldn't get these "h" and other letters, but I wasn't having 40 white rectangles on the screen. When I connected DB7 to GND instead of this symbols which don't work the screen displayed other symbols like "p", "q" etc. When DB7 is connected to Arduino (pin 12 in my case) then instead of any symbols the screen displayed 40 white rectangles. So the LCD doesn't behave like DB7 pin is always low I think...
5  Using Arduino / Displays / Re: Problem with some letters on LCD with LiquidCrystal on: November 11, 2011, 03:31:11 pm
Thanks for your help and explanation. Now I understand why it happens. I'll add a pot as soon as I buy one. I suspected that the potentiometer could do the trick here but I couldn't test it since I don't have any right now.

Any clues with the main problem? I checked my connection many times and everytime I find out that it's correct...
6  Using Arduino / Displays / Problem with some letters on LCD with LiquidCrystal on: November 11, 2011, 03:07:41 pm
I've just started playing with 16-pin 20x2 LCD screen and encountered many problems from the very beginning.
There is a problem with displaying some letters. I've just uploaded SerialDisplay demo from the LiquidCrystal library and here is what happens: if i send "a" (or "A") -> everything's okay, it is displayed on the LCD. Same with b, c, d, e, f, g. The problems start with "h" (and "H"). When I send this letter via serial monitor, on the screen appears 40 white rectangles. The same problem is with i, j, k, l, m, n, o. Then it's all fine with p, q, r, s, t, u, w, v. When I send x, y, z there appears 40 rectangles again and I can't see anything on the screen. If I send "ah", I have 40 rectangles again. If I send "ha" then it works fine, so there's no problem with displaying the "h" and other symbols themselves because they are displayed well if I send "ha", "ja", "xa" etc.
I've tried many demos and codes online but I always have the same result. I have rewired it all hundred times with no effect. I tried it on different pins too. Here is the connection I use now (most comfortable for me):
LCD pin   To
1      GND
2      VCC
3      GND
4      Ard-7
5      GND
6      Ard-8
11      Ard-9
12      Ard-10
13      Ard-11
14      Ard-12
15      VCC
16      GND
I use this code to initialize the library:
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);
I use this touch screen: (in Polish) and here is the datasheet: (in English).

I have no idea how to solve this problem and I've just run out of ideas. Do you have any suggestions?

Btw. I've also discovered some interesting fact with using LiquidCrystal: when I use this line
lcd.begin(20, 2);
the symbols on the LCD have black colour. If I don't use this line, they have white colour. Without the lcd.begin() line I I still can't display some letters. Why does the lcd.begin changes the text colour from white to black? White is much more visible on blue backlight. Is there a way to avoid it?

7  Using Arduino / General Electronics / Re: ATmega168 - what capacitors to use with resonator on: July 14, 2011, 07:28:27 am
Ok, so I don't get it. It's confusing...
So if I use this thing  I will have to buy two capacitors also.
BUT if I use this I won't have to buy any capacitors, right? Please tell me I'm right this time...
Attached chart shows 12-22pF for 16 MHz operation.
So it doesn't matter if it is 12pF or 22pF? So 18pF should be fine, right?
8  Using Arduino / General Electronics / Re: ATmega168 - what capacitors to use with resonator on: July 13, 2011, 08:21:39 pm
I meant crystal, sorry. Yeah, I think I know the difference between crystal and resonator. Resonator = crystal + capacitors, right?
So the last question: can I just use this - and forget about any capacitors? It is not labeled as resonator, but the description says it is 18pF, so I assume it is a resonator... Is 18pF ok? Or do I have to look for 22pF?
9  Using Arduino / General Electronics / ATmega168 - what capacitors to use with resonator on: July 13, 2011, 07:28:21 pm
I'm making schematics for my project, it is based on Arduino Pro Mini 5V/16MHz, but is using ATmega168 instead of 328.
The problem is I don't know what capacitors should I connect to the resonator. Pro Mini has some capacitors inside its resonator, but I have no idea what kind of capacitors these are, I can't read it from the Pro Mini schematics. I was searching on the internet and I found out that most people use 22pF capacitors on the resonator. Are 2x 22pF caps ok for the 16MHz resonator for ATmega168? If they are, another problem is that I can't find resonator with internal 22pF capacitors, I can only find with 18pF. Will 18pF be ok? I would rather use resonator with internal capacitors, instead of using a resonator and two additional capacitors.

10  Using Arduino / General Electronics / Re: Arduino Pro Mini parts + programming ATmega on: May 18, 2011, 02:15:55 pm
If you are connecting to RST anyway you don't need to worry about emulating DTR and the capacitor - that's a kludge for programming via the Rx/Tx pins with the Arduino bootloader.
Great, thank you very much for your help. So the final question - VCC also doesn't have to be connected to RST, right? Because on the arduino schematic it's connected to VCC through 10k resistor and DTR through 0.1uF capacitor, so both these connections can be omitted and I can leave RST pin on ATmega "open", right?
11  Using Arduino / General Electronics / Re: Arduino Pro Mini parts + programming ATmega on: May 16, 2011, 07:21:28 pm
Thank you very much for instant reply.
So, I will have to connect 14th LPT pin where DTR is now, right? Or can I connect it directly to RST and omit the capacitor and VCC? Unfortunately my electronic skills are very low so I have to ask every detail...

I know about avrdude, but I've never used it. I found this program and it has pretty nice GUI and looks simple, so I'd rather use it instead of avrdude. Will this program be okay for uploading hex files or I need to use avrdude?

I am using AnalogRead(); so AREF has to stay as it is.
12  Using Arduino / General Electronics / Arduino Pro Mini parts + programming ATmega on: May 16, 2011, 06:32:34 pm
Hello guys,
I have few questions for you and I'd be really grateful if someone could answer them smiley
I've been programming arduino for few months and I know all the basics. I even started my small little project and few friends are interested in buying it. So I decided to pay some company to make me couple of PCBs according to my schematics. I don't really want to solder all these LEDs, resistors, etc. every time, so making a custom PCB with ATmega and my components seems pretty reasonable.
My project is based on Arduino Pro Mini, so I had to base the schematics on it.

And now the questions:
Here are the Pro Mini schematics. U2 is a voltage regulator, but what about other elements (JP1, JP2, JP7)? What are they? And also, are all of the connections necessary on the ATmega? I think resonator (PB6 and PB7) is necessary, but what about all the others? Do I have to connect reset to DTR and have all these capacitors and resistors? What is AREF pin and why is it connected to GND, and why through a capacitor (C1)? Why there's VCC connected to GND through a capacitor (C3), on the bottom left from the ATmega? What does it mean and is it even necessary? I'm a little bit lost in all these information, but I'm trying as hard as I can to understand all of this.

And now about programming ATmega:
So far I've been programming Arduino using IDE, and sending the code using TX, RX and RST pins. I've been doing some researches and here is what I managed to understand: I won't have an arduino bootloader on the ATmega bought in a shop, so I need to send the program differently. I need USB or LPT programmer and connect it to RST, MOSI (D11), SCK (D13), MISO (D12) and GND on the ATmega. I also need application which would send hex file (compiled for ATmega168, which I'm going to use*) to my ATmega, like this one
I'm going to make my own programmer through LPT port and connect specific LPT pins directly to ATmega pins (14 > RESET; 16 > MOSI; 17 > SCK; 10 > MISO; 25 > GND). My computer is not equipped with LPT port, and I'm going to use standard LPT > USB converter. Won't this cause any problems?
Are all these information correct? Does it work that way or I misunderstood something? Is that application (link above) good for sending programs to ATmega? Please correct me if I wrote something wrong

*I know Pro Mini uses ATmega328 now, but 168 is cheaper and will work just fine with my project.

Sorry for my English.

P.S. The only elements on arduino are ATmega, resonator, voltage regulator, resistors, capacitors and LEDs, right? Or are there any others?
13  Forum 2005-2010 (read only) / Development / Re: Help- using an arduino to make a midi controller on: November 14, 2010, 05:19:36 pm
Start it with reading the touch pad position. Do just this, and send it using Serial.print and read using serial monitor in Arduino IDE. You can easilly find code for reading touch pad position. Then, if you get the position reading part right, you can start adding new elements, like hold button or LED. Don't even try to connect everything at once because you get lost. Do everything step by step, starting from the basics.
14  Forum 2005-2010 (read only) / Development / Re: Help- using an arduino to make a midi controller on: November 14, 2010, 01:44:09 pm
Man, we've spent months working hard on this project and you want us to share everything we did? It doesn't work that way.
Buy arduino, buy everything that is needed to make it work, get familiar with arduino IDE and then, if you find some problem you can't solve, ask us and we'll tell you. But don't expect complete how-to or complete code.

EDIT: When I started this project I knew absolutely nothing about programming and absolutely nothing about electronics. So, I think this project has been the most educating thing that I've ever done. Keep this in mind and do it yourself.
15  Forum 2005-2010 (read only) / Development / Re: Help- using an arduino to make a midi controller on: November 10, 2010, 01:57:39 pm
Send turn pad off if y == 0 and x == 0 (in the main loop).
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