MAX7456 On Screen Display Module and Arduino

Development Boards Arduino
1

Anyone successful at getting the SparkFun OSD to work with the Arduino?

I’ve downloaded the sample code and made connections to the OSD module including a 100Ohm resistor to RST to 5v, and HSync also to a pull-up. I get a picture, but the Arduino still waits for the file download after using HyperTerm or other comm software. I’m sending MAX7456 Demo.mcm file to the OSD module but no result. I’ve downloaded other Sparkfun OSD module (Arduino) .pde too and no result.

Any all-in-one solution available?

Thanks in advanced!

2

If you look though the comments KiwiJohn posted a demo on his site [<LINK_TEXT text=“http://www.john.geek.nz/2011/01/adding- … generator/”>http://www.john.geek.nz/2011/01/adding-custom-characters-to-the-max7456-video-overlay-generator/</LINK_TEXT>

I followed this and got it to work just fine.

I also wrote a program to generate the code for making characters for the chip [<LINK_TEXT text=“https://sites.google.com/site/qeewiki/p … 6-img-gen/”>https://sites.google.com/site/qeewiki/projects/q-s-max7456-img-gen/</LINK_TEXT>

Try johns code first.

Cheers

Q](https://sites.google.com/site/qeewiki/projects/q-s-max7456-img-gen/)](Adding Custom Characters to the MAX7456 Video Overlay Generator – john.geek.nz)

3

Does this mean that the character set comes preloaded with the MAX7456?

I need to determine if my module is bad. I connected all the points required by the tech data sheet and various Arduino code. Can you provide a pin connection layout and ‘drag and drop’ code to work? Based on the “Waiting for data” display of the code I have loaded, it requires/requests an .mcm file and that is keying me that the character set is not loaded.

That said, what code can I load to Arduion just to bring up “Hello world”? I should be able to work from there.

Warm regards,

Doyle

4

The max7456 module I purchased here worked sometimes. The surface mounted max7456 was not soldered correctly. As soon as I re-soldered the pins, it worked.

The sample code did not work unless I pressed down on the max7456 chip.

5

hey qema,

changing the character set seems very important to everyone who gets the max7456 working. why? maybe someone else can answer if no reply. It is very confusing to new users. There are so many posts about flashing new characters. more posts than how to use the board without flashing new characters.

This is still confusing to me. I have the board working with the sketch that overlays SAMPLE in the middle. Although that is the only sketch I have found so far except the ones that you run to change the characters and the ones to test the change. Haven’t found any others yet. The sample sketch is a real achievement for the author but it leaves little for someone who wants to use the board to overlay text on video.

It is difficult to find any way to move the text to the top. The x value works for left to right but the y value is not available. Then you have the letters as long as you don’t mind calling S 08 along with three other 0x04 numbers for example. Looks like fun if you want your text to change based on data received. Just wondering

Thanks

6

Here is one of the answers to my questions. Why does it seem so important to change the character set. The answer? To make it easier! That is as long as you get passed the changing of the character set which has blown many a newbies night/nights? I am one of these, embarrasing as it might be. Probably have tried to change the char set 30 times doing something a little different everytime and reading instructions on how to do it every fifth time. Even got the message that indicates the file was sent. Still no joy. It is still something you want to do because it will make it easier. How? to quote dfraser;

" As it comes from Maxim (max7456) the default burned in fonts are incomplete and in a rather strange order. This means if you are sending ascii data to the arduino for the MAX7456 to print on screen you have to use a rather convoluted lookup table." So newbie reads "if you don’t change the fonts you will have to write a lookup table! (god forbid)

This is why the original poster of this subject was trying to change the font set.

Anyone with this same problem, it seems that it is more important to first get the the board running correctly with the SAMPL E sketch by Pete Dokter on 6/7/09 that is the sample code Sparkfun refers you to at the bottom of the product info page for the breakout board. This requires nothing but wiring the breakout board correctly to the arduino and uploading the sketch. There can be a success before you move on.

I believe this is the very first step to take unless you are very familiar with arduino and can remember what is really important from the 13 page forum subject where the quote came from. arduino forum “Arduino + MAX7456 OSD”

7

So here is the Sparkfun Max 7456 breakout board running the sample sketch talked about in the previous message.

No I guess it isn’t going to be here because you can’t paste jpegs into this forum. (but it’s easy! others have done it!) No, posting it somewhere else to link to it is not as easy as paste you’re done.

Anyway, it is a picture of the breakout board wired to the arduino with SAMPLE on the screen in the background so you could see how it is hooked up and that it works. Being able to post pictures quickly and easily would promote more precise flow of data. Using words to describe things is not as exact as a picture. but I digress . . .

hook up goes like this in the sketch;

#define RESET 0 //PB0

#define CS 2 //PB2

#define MOSI 3 //PB3

#define MISO4 //PB4

#define SCK 5 //PB5

So this is fun for a new person PB0, 2,3, . . . This is like being in someones neighborhood and not knowing they call XYZ street RiverRoad. On the map it’s XYZ everywhere. “Well then” they say, “you’re not looking at the right map!” “Everyone round here uses the map ya get at the drugstore in town.”

You’re not from around here are ya?.!"

So every time someone says, “I followed this and got it to work just fine”, as advice on how to do something you should just say, “You’re not from around here are ya?.!”

but I digress . . . .

So now I move on to getting another sketch to work from where I am at. Going to dfrasers message at the beginning of the 13 page Max7456 discussion he leaves two parts of a sketch that looks like it should help in making this more workable. Make the sketch our of both parts and it doesn’t work. Pin assignments

#define DATAOUT 11 // MOSI exactly what it says

#define DATAIN 12 // MISO exactly what it says

#define SPICLOCK 13//sck

#define MAX7456SELECT 10//ss

#define VSYNC 2 //INT0

So I’m not from around here, can someone help me to the history why this hooks up differently?

Is MOSI in or out?

Is ss also known around here as cs?

Off to look for some sketches that will work with the SAMPLE sketch setup.

If anyone knows way to find them, search terms, links, ect. it would be appreciated

8

MOSI= Master Out Slave In

MISO= Master In Slave Out

Just like Serial Tx and Rx, you need to cross the two communications device; Tx → Rx and Rx → Tx; so MOSI → MISO and MISO → MOSI. This ensures direct communications.

Look like you are on the right track. I shifted to the OSD-232 module from Intuitive Circuits; http://www.icircuits.com/store/prod_osd232_plus.html

This is VERY easy to work with and has lots of features. Basically it uses the MAX7456 with a microcontroller. You send serial commands for positioning and character selection. It saved me many hours of trying to code and develop a character table. I had to upload different tables each time but with the OSD-232, life was EASY!!

Keep up the good work!

9

Maleche thanks for the reply!

Came across that MISO info later today. Haven’t found a sketch yet that works with the SAMPLE setup. Moving the blinking word left right and down is possible but going up is beyond me. It is amazing how many things in that sketch you can set to zero with nothing happening at all. What initiates the placement of x into row 12 or 13 from the very start really has me baffled.

Thanks for the suggestion I will have to check that out. Even though I would love to play with the arduino all day getting something done has to be more important. The something done involves text overlaid on video preferably with arduino.

The Nootropic board works well for my needs. I was checking out the options. Evaluation time is over for this one. Great puzzle though.

Thanks again for the reply

10

Maleche:
MOSI= Master Out Slave In

MISO= Master In Slave Out

Just like Serial Tx and Rx, you need to cross the two communications device; Tx → Rx and Rx → Tx; so MOSI → MISO and MISO → MOSI. This ensures direct communications.

Maleche,

On what are you basing that advice? My understanding of SPI, which is supported by this [explanation on the Arduino site and [this tutorial from SparkFun, is that MOSI is to be wired to MOSI and MISO is to be wired to MISO.

SPI is a mastered bus, that is one of the devices is “in charge” and controls the bus and the other devices on it. Put another way, SPI is not a peer-to-peer system; not all of the devices are equal. Having a master allows putting more than two devices on a bus, so that each bus requires only 3 (MOSI, MISO, SCK)+s signal lines, where s is the number of slave devices, each of which has a SS (slave select) line.

Eric](http://www.sparkfun.com/tutorials/65)](SPI - Arduino Reference)

11

Works for me.

12

I cannot get my MAX7456 to overlay anything on the video

I’ve

I have it all wired correctly

I’ve tested it for proper voltage

Video passes through it

It’s just not overlaying anything to the video.

I also have the resistor 1.5K ohm between reset and 5v. I don’t understand: resistor 1.5k ohm, it is effect ?

13

Hi;

I have one confusion about MAX7456 usage with AVR arduino or bus pirate board.Since sparkfun breakout board of max7456 consists of spi interface so why to use arduino controller or bus pirate board.Why one cannot directly interface breakout board with computer COM port using RS232 to spi converter and give command through com port or make its own program in C language for what to display.Can anybody give detailed explanation of why to arduino or pirate board is compulsory.Remember bus pirate board uses python script which uses pyBusPirateLite Library.

I will be very greatfull to you if you help me solve this issue.

Regards;

Uzair.

14

I am experiencing same thing…did you ever get it working or did you abandon for lack of support…

anhminh81:
I cannot get my MAX7456 to overlay anything on the video

I’ve

I have it all wired correctly

I’ve tested it for proper voltage

Video passes through it

It’s just not overlaying anything to the video.

I also have the resistor 1.5K ohm between reset and 5v. I don’t understand: resistor 1.5k ohm, it is effect ?

15

Well… that is now three of us by the looks of it…

I’ve got my Breakout board wired as per all schematics, including resistors.

Reset is HIGH.

Separate power supply.

Video is displaying on screen, but NO text is displayed using ANY of the Samples I have found.

I have not tried changing character set, because I cant even get the native one to work…

Only other thing I have NOT tried is verifying the IC is soldered correctly…

TO make it even MORE confusing… I DID see “Hello World” once on screen…

I uploaded the HELLO WORLD sketch, nothing…

I was pouring over the code… trying to figure it out…

I chanced to look up at the screen… maybe 45 seconds later… and there it was HELLO WORLD, top left corner…

Cycled power on everything… NOTHING… have not been able to recreate since… just slowing pulling my hair out…

@SPARKFUN: Anyone care to offer some support? (Or accept returns!)

16

I expect the OP moved on a while back, but hopefully this may help other people with the same problem.

I had the same issue but SOLVED it as follows:

I wrote a very simple program to read the STAT register via SPI and print the result to the serial port. Initially it returned 0’s all the time so I knew that was wrong. I then noticed that if I put my hand near the breadboard I got an occasional non zero number. That reminded me of a post that mentioned length of jumper wires as a problem, so I swapped the 20cm wires to 10cm wires and suddenly I got the correct values being read from the STAT register! I then loaded up the original code from the site where I got the board from and it all worked perfectly.

Reading the STAT register is simply a matter of sending the register address (0xA0 I think) and then sending a dummy byte while reading the result. I.e. something like :

digitalWrite(selectPin, LOW);

spi.transfer(0xA0);

byte stat = spi.transfer(0);

digitalWrite(selectPin, HIGH);

serial.print(stat)

If you unplug your video source you should see the stat register value change as it includes a bit for PAL detected and one for NTSC detected. You will also see occasional changes due to vertical and horizontal blanking flags.

If you still don’t get a sensible value being read, check the MOSI pin on the arduino is connected to the DataIn on the MAX7456 board, and MISO to the DataOut (plus obviously the CLOCK and CS connections).