MinimOSD Module for ATV

Recently I have been working on a way of adding a text overlay to my video for ATV transmission. My chosen method was to use MinimOSD Module. I posted about my initial trials and testing here. In this post I will go through the whole process of installing and configuring the MinimOSD Module for ATV use.


The minimOSD modules are programed using the Adruino IDE. This is because on each minimOSD board is an atmega328 chip. This is the same as found on many Arduino boards. This chip then controls the OSD chip, telling it what to overlay onto the video.

My Current code is available on my Github. From here you can download this and then edit it to your calsign etc…


The first step is to modify the font file to your liking. This is where you can create custom images / text to display on the screen.

To do this you must have JAVA installed, this is available here.

Now open MAX7456Charwizard.jar in the ‘MAX7456FONTS’ Folder.

MAX7456 MCM Wizard

From here ‘File – Open’ ‘MY_CUSTOM_FONTS.MCM’. This is my personalised Font File which has already been changed specifically for the MinimOSD Module for ATV use. This shows the blocks you need to edit to show your callsign. If you have a 6 character callsign you will need to change the /P section to the last character of your callsign. If you have the same letter twice in your callsign then you could put your 6th character there if you wish but you will then need to edit the Adruino code yourself to make this work. Also if you have less characters then you can set the unused charterers to blank blocks.

MAX7456 MCM Wizard open Font file

TIP: Always remember to click save character after making an edit.
TIP 2: When making large letters you have to design the sections of the letter as is the borders are not there. In my example see how the diagonal sections the edges don’t line up.

You edit each section by colouring the squares.

MAX7456 MCM Wizard Edit Font File for the MinimOSD for ATV

Transferring the Fonts to the MinimOSD Board

Next you need to connect your OSD module to your PC using a RS232 to usb (FTDI) adaptor.

Making sure you get all the connections between the two correct use the following image for help.

Connections of the MinimOSD to the RS232 FTDI Adaptor


There are a few ways of powering the board. The board is effectively two boards stuck together with some data control lines between the two. The power to each side is separate.

Method 1: The default way is to power one end with 5v, the end where you connect the FTDI adaptor and the other end where the video connections are with 6-12v. The 5v can be supplied directly from the RS232 adaptor board using the VCC pin as shown above.

Method 2 & 3: On the board there are two sets of jumper pads which connect the 5v rails of each board together and the other connects the ground planes together. This means you can either power the whole board with the 5v on the RS232 end or the 6-12v on the OSD end… but not both.

If you do used the 6-12v side then do not use any more then 12v or the on board 5v regulator will overheat. Also if you do use the 6-12v side to power the whole board then disconect the VCC to +5v wire between the RS232 adaptor and the minumosd Board.

Connections of the MinimOSD Board

Above shows the 6-12v connection on the OSD Board. there are 2 pins for VCC and 2 for Ground. the two pins of each are connected together.

Transferring the Font File

Now you have the OSD board connected to your pc through the RS232 adaptor board you now transfer your new font to the OSD module.

To do this you need to install the Arduino IDE from the website. Then install teraterm-4.100.exe. An install file for this is included as part of the github download.

Open the arduino IDE and load the code ‘MAX7456FONTS.ino’ from the MAX7456FONTS Folder. In the arduino IDE select tools at the top and set the board to “BOARD TYPE” and the port to the port of your FTDI adaptor.

Now Upload the code to your arduino.

Adruino IDE Program Upload MAX7456FONTS.ino to allow updating of fonts on the MinimOSD for ATV board

Now launch the teraterm program, connect using a ‘COM’ serial connection. This will be the same COM port you selected in the Arduino Program.

Tera Term Software. MinimOSD for ATV Font changer welcome screen

If you do not see the following text on the Teraterm program press the reset button n the OSD board and try opening the program again and connecting.

Now go File —> Send File….

Tera Term Software. Send File

Now select your custom Fonts file that you edited earlier.

Tera Term Software. Select My Custom Fonts

The program will now send the new fonts file to the OSD chip on the Board.

Tera Term Software. Sending Progress

Once the above window disappears the black window will appear frozen. Press ‘Enter’ while in this window and it should update to say ‘Done with font file download’

Tera Term Software. Sending completed

You can now close this program.

Arduino Programming (The program that tells the MinimOSD whats to display)

Open the IDE and open the ‘MY_STATIC_OSD_V1.0’ to get the basic setup working. ‘MY_SWITCHED_OSD_V1.0’ is modified to allow the use of switches to turn different text on and off and will be explained later in the post.

Edit lines 21 to 25. The first two change the text shown on lines one and two. The third selects whether to show the large callsign or not, this is the one you will of edited in the FONTS file previously. The forth selects if you are showing a 5 of 6 digit call. The 5th sets how long the large call is displayed on the screen in milliseconds.

Arduino IDE My Static OSD Setup and uploading

Once you have done this you can now upload this code to the minimOSD module.

Hardware Install

Now you have the FONTS and the arduino code loaded on the OSD module you are ready to install the board into your project.

MinimOSD for ATV Board Video In and Out Connections

Identified above is the Video In and Out connections along with the 6-12v connection mentioned earlier.

This is how I have currently for this setup with an adidional 2 switches on top to change what is on the screen.

I will post any future updates to the MinimOSD Module for ATV and add links from here so you won’t miss them.

Also please comment below with any questions or ideas. I am learning this as I go along so any feedback is most welcome.

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