MobiFlight Community Support

Welcome to the forum for MobiFlight! Feel free to reach out to the community in case you have questions, issues or just want to share great ideas or details about your latest home cockpit project.

You like MobiFlight? Donate via PayPal and support the MobiFlight development. Thanks! 

icon
Avatar
Caspajack
Posts: 29
Hi All,

I been worrking on some MAX 7219 boards to create some radio equipment COM, NAv etc.
Initially I used a couple of the usual MAX units with 8 digits from eBay, using a dual encoder and a standard monentary switch to swap from standby to active.
That all works perfectly, so I ordered some 5 digit LEDs from China and a few of the smaller MAX 7219 boards, (the ones with 8x8 Matrix LEDS) to use instead of the longer ones with the 7 segment LEDs.
I used a schematic of both the MAX 7219 chip and the board the Matrix was mounted on, then rigged up a test with some flying leads to the correct pins on the new 5 digit diaplys, It does work fine but the digits are shown backwards.
For example the test function normally shows 123.45 but on this settuo it shows 543.21. Of course I can fix it by simply changing the digit wiriing, but after checking it is wired as per the schematic, so I wondered if there was another setting I have not thought about,
Incidentally I used the example config from the Mobi dropdown to set it up.

I've designed a board to mount the displays and the MAX 7219 on, which will then only require five wires to the Arduino.

Thanks
John.
2019-07-15 18:27
Avatar
pizman82
Moderator
From: ETSI, Germany
Posts: 3695
Supporter
I don´t know the wire logic ( and pcb setup) of those 8x8 Matrix Boards ..... In case most users use the 8 Digit Tubes.
By the way..... You also can order 8 Digit Tubes with removeable Diggits..... After pull off the 2x4 Diggits you got also 2x12 Pin rows where you can set your custom Displays.

About your Problem..... I Think you got simply a logical issue....

If the Diggits show a correct number but just the sequence change from Left--Right into Right Left then the "numbering logic" is inverted.

Stephan said something simmular in the past..... So the Digit 1 Pin means the most Right Diggit ( 8 in Mobiflight and your logic) .... And Dig8 is logical the Left one.

I don´t know if this is a manifactur problem or if the issue is in Mobiflight System that send the numbers in wrong direction.....

But solution is already known youreself.... Simply change DIG1-Dig8 Wires into inverted direction.
Good Luck !
2019-07-16 06:59
Avatar
Caspajack
Posts: 29
Thanks pizman82

As you say I have a solution but it's annoying that I have to change the wires from the published schematic.

In order to get the layout of the 8x8 matrix board, I traced the tracks with a continuity tester. Probing the MAX7219 and the pins on the PCB, of course after removing the 8x8 Matrix from the board. Then I checked each pin against the pinout of the MAX7219 circuit diagram. Using this information together with the pinout of the new LEDs; so I'm (fairly) confident that the pins are wired correctly.
I wanted to use the smaller footprint of the Matrix boards to make the layout a bit neater at the back of the radio panels. These are going to be fitted to my 737 simulator. At the moment I use some GoFlight radio gear but they have a habit of disconnecting in the middle of a flight, because each radio takes up a separate USB socket. I do use powered hubs but it still happens, I thought with a single arduino (and MobiFlight) I could run all the radios and more from a single USB socket.

I’ve found there are two types of MATRIX boards, one has the full size chip alongside the MATRIX display, and the other uses a smaller chip in the centre of the board; and unsurprisingly their PCB layouts are different.

If no one can offer a solution I will simply rewire the 5 digit pins to force the LED to display correctly. However it would have been more satisfying to know if it’s a MobiFlight software issue, or some fault I have introduced.
Thanks again
John.
2019-07-16 09:40
Avatar
pizman82
Moderator
From: ETSI, Germany
Posts: 3695
Supporter
Maby Stephan can tell you that with more details.....

For me the idea is simple.... Sebastian write the code for use with the 2x4 Digit Tubes..... and THERE it work fine. So this means (i think) in those Tubes the Diggits are Also inverted.... So DIG1 Pin of Max Chip is connected to the DIG4 socket of the RIGHT 1x4 Display..... To compence this pretty sure Mobiflight simply send the Numbers in a way that "invert" the sequence to have a correct result on the Premade Tubes.

In the Matrix Board the situation is not fixed to one state..... If you simply turn your Matrix ( look on it from behind) the System is mirror inverted.... So you can not say "Dig1" means the firt collumn .... From behind its the "last" . Or you turn it in frontview by 180° ..... Then Row1/Col1 change into 8/8.

*******

If you like you can buy a 8 Diggit Tube and you can research the PCB Lines.... If my Idea is correct then the DIG1 Line from Max7219 is wired as i said above.

Solution:
Rewire .... OR .... Rework of Mobiflight Code. But here pretty sure Sebastian will not do this (Cause it workes as it should with tubes, that are used by 99% of customers)
If you can programming yourself you can rework Mobiflight source code for your own usage.
Good Luck !
2019-07-16 22:16
Avatar
Caspajack
Posts: 29
Ah! now that makes sense, I had not checked the actual position on the original 4x4 digit PCBs.

When I traced the tracks it's as you said, Digit 0 is the first digit on the left, looking from the top with the input pins on the left, so the MobiFlight code must invert them to display the digits in the order required.
I thank you for explaining this, I would certainy not expect Sebastian to rework the code, which obviously works perfectly for the original layout,

So I can now rewire the order of the digits to display them correctly. I can also order the new PCBs once I have reworked the tracks as well.

Is it possible to insert an image from my PC? I could then show my progress to the forum.

Thanks pixman82.
John
2019-07-17 07:50
Avatar
pizman82
Moderator
From: ETSI, Germany
Posts: 3695
Supporter
Sorry....
Its not possible to upload pictures here.... If you like this you need to upload it "somewhere" For example a filehoster or on your own webspace..... Then you can link this adresses here or use it as a "picture" by the button above.

At last..... If i remmeber right the same problem happend for a other user in the past.... but much more painfull..... He designed a PCB for the B737 MCP with included MaxChips (single Chips without Tube or Matrix Board) and all Displays build with 1 Dig Displays in rows.

Finaly he did the same mistakes and all Displays was inverted..... But he can´t rewire it cause all wires was just Lines on PCB incluing the chips itself.
So he need to completly redesign the PCB´s and order it again for lots of money.

So.... Keep Cool. Your case is just a bit of work but not a fully desaster like that.
Good Luck !
2019-07-17 19:57
Avatar
Caspajack
Posts: 29
Wow! I'm glad I asked a few questions here before ordering my PCBs. To start all over again must have hurt!

So when I've got some of these parts ready, I will host some images on my cloud and link them here.
I've orderd some more LEDs, 6 digit this time for the 737 radios and a few more of the MAX Matrix style tubes which fit better behind the 737 panels.

Thank you once again pizman82 for you advice and patience.

Kind regards
John.
2019-07-18 07:33
icon