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Posts: 41

Have built my pedestal panels and am trying to get the CHF1 and NAV1 to work.
So far I have managed to program the Mobiflight connector with my Arduino 2560 board for my 7 segment displays.
So far so good.

Now when I connect it to P3Dv4 and PMDG the display is showing very wrong values.

What I have used are the following values and settings in Mobilflight;
Offset 0x034E
Value type Int
Size in bytes 2

Compare tab:
Apply comparsion ticked
set it to: $+10000
else set it to: $+10000

Display tab:
Everything set in the upper boxes so it fits with the displays.
Use left padding ticked and value 0

When I press test it works fine and shows 123.45
Then when I connect to PMDG and make it run the radio is set to:
128.42 and my display shows the first three digits fine 128.4 but then I get a very disturbed second digit, it looks like a 6 turned upside down but not all segments light up, the upper middle part does not light up.

When I look at the output value in Mobiflight it says: 12842
And that is correct. But my display does not show that.
What can I have done wrong here?

Have tested with all 8 digits same thing for all.

Can someone help me with this problem?
2018-07-31 18:48
From: EDDG, Germany
Posts: 1819
Hi sebpil,

I think, you do not need the comparision tab. You should use the transform with an activ hook and the contents $+10000.
Lat but not least activate the hook at BCD-Mode.
Stephan (Time: UTC+1)
2018-07-31 19:33
From: ETSI, Germany
Posts: 5571

Do we talk about COM1 Active Frequency at the moment ???

Basicly PMDG is not the Problem here.... pretty shure you got same result also in the standard cessna for example ( Cause PMDG work with main P3D System here)

About Problem.

1. Basicly i think ( not tested it at the moment) you not need Left Padding here... after $+10000 the Value is always 5 diggits long... So there never can become a situation you have a leading Zero i think. So i would remove the Left padding setting at first.

2. Check if a other Config will use the problematic Diggit at same moment. If a Display flickering or show stupid things mostly a second config try to write on it same time. to get shure here simply create a complete NEW Mobiflight File.... Only setup ONE config for your Com1 display.
And now test it.

3. Confirm Problem is always on same number or problem is always on same Diggit.... so test for example Digits 123.45XXX and in a second Run with diggits XXX456.78 active.... Is Problem always the second decimal or is Problematic Diggit always Number 5 for eample... So in test 1 +++,+X and in test 2: +X++,++ ( X= problematic Diggit)

4. Please confirm you activat the BCD Mode enable like needed for COM Frequency Offsets !

5. Confirm you use ONE 7 Segemnt Display (Max7219) for this or do you have more tubes set in a row (chain).... If chained please also confirm the Com1 Display is set to ONE Tube....Not splitted via 2 Displays ( like Diggit 1234 on Maxtube 1 and Digit 5 on Maxtube2.

6. Important.... If you use more then 1 Display in a row.... Please confirm you wire the 5v Power line directly to EACH Displaytube single. Or remove the brake diode on the tube by yourself..... If you wire it 5v from 1 display (Output Connector right side) to next Display Input conector this can not work in case of a construction issue of the Max Tubes !

In case this is never reported i´m pretty shure we can find your problem !
Simply reply my questions or report if you find the problem youreself !
Good Luck !
2018-07-31 19:34
Posts: 41
Good day and thank you very much for your reply.

Will make it a bit more clear.

Yes I have it in BCD mode.
Left padding ios removed

I use two MAX7219 displays in chain but only use the left one when I program it.

I have programmed my MCP without any problems at all using the same interface cards and that is a problem, the MCP works great!

Now when I have connected my displays to the arduino I use 5V, GNC and 22, 24, 26 ports on my Arduino Mega 2560.
They are correct setup and uploaded to the card. No errors.

Now when I start the display = when it is connected to the USB port, all digits show 8 in my case like this

So far so good.
Now lets go back to your question list;
1, Left padding removed
2, Cannot check that since now when I press the test button, nothing happens still only the startup digits
So I restart everything including Mobiflight software, same problem only the 8 rows

3, Cannot cofirm that now
4, BCD mode is enabled
5, Two in chains but the correct values are set, I am sorry but I do not know how to show images here, that would be much better but it seems impossible to show images, right?
Once again, I have set the values for display like this;
Use type of: Display module ( I do not know if this is correct since I have added a 7 segment display in the menu Extra -> MobiFlight Modules
Address/connector COM1 (my name for the display) / 1 (for display 1)
Number of digits 8 and then NO left padding
Use display 2, 3, 4, 5, 6
Set decimal to 4

6, This I do not get. I have not made as you say on my MCP and that works fine. What brake diode?
Never heard of that.
Again it is extremely sad I cannot upload images here so I can show you as images say more than thousand words.

And now I get an upload error.
I think there are a lot of problems here. Arduino boards seem to generate errors as they like. Sometimes when I restart my cards by remove and insert the USB then programming and upload is okay and sometimes not.
Maybe there are better interface cards to use?
2018-07-31 20:18
Posts: 41
Now I restarted everything again!
Then when I press the test button in mobiflight all light up.........not the displays I want.

Well I quit today, too much problems right now, I do not have the energy right now. Have spent the entire day trying to get this to work.

Thank you for all your replies here, continue and I will read and try every solution and let you know if I am helped by anything.
2018-07-31 20:23
From: ETSI, Germany
Posts: 5571
No prob.... Get out of your cockpit construction side for some hours..... with new energy all seem to be a bit better next time :P

About Problem....

Now we get closer....

If a Display show 88888888 instead of correct Data then this is in 99% of situations a hardware error.
Mostly when in testing proces the Displays are not soldered..... only wired improvisional then those errors ocure.

Note: max Displays are verry sensitive. Touching just a not wired cable ( a little vibration on Table can be enough) will kill the hole system. Then you must Restart the Arduino ( Get it out of power for some seconds so the cipset will initialised completely new.

So i can not tell you.....
- The issue can be temporaray in case of a not solder cable.....
- It can be all time in case of a soldered cable that is not 100% correct in contact ( In that case you should resolder all 5 (10) contacts left/Right on the tube. Whatever they was already soldered when you buy it..... My expirience is that maby 20-30% of China Import Displays are broke when you get it.
- Whorst Case..... The Display tube is completly killed ( Maby Hot solder or a internal Issue )

For Testing....
Try to find the issue spot.
Test differen Displays....
Test different Pins ( Maby on your Mega there is one Pin dead)
Test a different Mega
And again check all solder contacts and NOT use improvisional Jumper wire or Breadboard cosntructions with Max7219 Chips !

About the Diode.... Its on the Back ( Use Forum search or google) It will reduce power in Tube by 0,7v ... Thats correct for ONE Tube.... But problem is that the Output Power on the right now support only 4,3v instead of 5.0 ...... On a 3rd Display in a row the output is then only 3,6v the will have 2,9 and can stop working at all time.
Thats why it high recommend to remove dhis diode OR simply wired the 5v direct from Mega to each single tube ( The other lines 3x Dtaa and GRD can be shared from tube to tube already.

AND.... I forget before.... While Testing... Please test simply your tubes Single ( not in a chain) If it work ....But not in the Chain then we know 100% the issue is in the Display that is set "before" this one in the chain..... Mostly the CLK or DOUT Pin on the Right of the other Display is broke in that situations.
[Last edited by pizman82, 2018-07-31 20:53]
Good Luck !
2018-07-31 20:47
Posts: 41
Good morning.
Well now I have tried everything again. Still the same only eights all over my display, nothing wrong with cables. I have been in electronics manufacturing for 20 years so my experience with professional products is very extensive. But this arduino looks like an over charged product that cannot do much if it is that sensitive.
It is impossible to not touch a table or construction where the displays are mounted.
It can not be that sensitive.

But okay I will work a bit more and then scrap my project until there are better products available on the market.
Arduino does simply not meet the requirements everyone should have on electronics like this.

If anyone has an example of other interface cards that can control displays, let me know. Am getting very tired of arduino junk.

When it comes to the MAX7219 there are 12 connectors, not 10 to the display module. There are 5 connectors on the left side and right side. The right side only for chaining them.

Beleive me I have tried to fins the issue spot by doing everything you can in the electronics world. There is nothing wrong electronical with cables or so. Nothing whatsoever.
I know products from China is only JUNK and nobody should ever work with chinese junk when it comes to elecotrnics, all they can do is pirate copies of good products. Unfortunately most of the large manufacturers of electronics have placed their manufacture in China and that is extremely sad. So it does not matter where you buy your displays from. They are to 99.9% manufactured in China today, and that is very, very sad.

Have also tried another arduino board, same problem. My displays are glued into place after they were tested on the table and they work. They simply just do not die from nothing. I work in a completely anti-static area when I build the electronics for my simulator. Spending years trying to figure out how arduino boards work, is not my type of life. There is simple not a single manual how to use these cards on the market, what the limitations are for 5V etc.

My idea was to give my displays an external power source of 5V that is not supplied from the arduino board. Has anyone tried that?
Is it possible to just use the arduino board to control the display data or do you need to connect the 5V and ground to the arduino only?

There are alot of questions about these arduino boards I have and if someone has an english manual please let me know.
I will keep you updated on how the project is going and if I find a solution.

Am very, very thankful for your support here. You are great and really trying to do your best, that is very much appreciated!!
Thank you all. We will find a solution for everyone so that the arduino boards, or a better interface card, can be used that is not that sensitive.

Have a wonderful day everone and enjoy summer while it lasts.
2018-08-01 09:24
Posts: 41
As I understand you should be able to chain 8 displays, right?
I have never managed to chain more than 2. Can that have something to do with the 5V diode?

That is why I wonder if it is possible to give the 5V to each module from an external source instead of the arduino which is not capable of supplying power to 8 display boards. Or at least, since there is no technical data available for arduino, this must be assumed.

If the display modules in Moboflight is set to be able to chain i series of 8 display modules then you should be able to use it and not only two.

Will wait for a reply to this.

Once again I have checked the wires on my setup, there is nothing wrong here.
Have also changed display modules several times and nothing works. Arduino board is changed, doesn't work.
No short circuits anywhere, 100% sure all wires are perfect.

Latest mobiflight software used.

MAYDAY this looks very hard to solve. There must be more people than me that experiences this. Let us share knowledge here. Thank you.
2018-08-01 11:12
Posts: 41

Well the third arduino board has been tested now.
Now it works almost okay. Some digits not okay.

Still I believe that this has nothing to do with my displays since they work correct when tested on the table in same configuration as in the panel I have done.

Sometimes when I connect the arduino and test it, it works, the digits not 100% correct.
It needs ALOT of restarts of arduino and in and out of USB cable until it works. And this is not acceptable.

In this case it will take several hours before I can start a flight just to set up the displays.
There must be a better way to control displays?

Mobiflight itself is nice to use and easy. I like it but the communication with the arduino from the software seems complicated and it does what it likes and not what it is programmed to do. Not a single other user having the same problem?
2018-08-01 11:52
From: EDDG, Germany
Posts: 1819
Hi sebpil,

as you describe your problem, it sounds very depressed.

But head up, to my knowledge, you would be the first to fail.

Fundamentals of the diode on the board:

This diode is used for reverse polarity protection. It protects the MAX chip, which would be directly defective in case of reverse polarity.
You may be aware and pizman has already pointed out that over a silicon diode in operation, a voltage of 0.7V drops. Thus, the actual operating voltage of the 1st board is 4.3V. When building a daisy chain, the voltage of each board is reduced by 0.7V, the second 3.6V, the 3. 2.9V. According to the data sheet, the MAX7219 needs at least 3.4 volts for safe operation, including working indifferently.

There are two approaches here. The first is to control each board individually with 5V, then all boards work with 4.3V. The second approach is to remove the protection diode from the board and replace it with a wire jumper. Then all boards work with 5V.

In variant 2, it does not matter if the boards are supplied with voltage from the Arduino or from an external power source. I have a total of 14 displays active, including 8 and 6 in a daisy chain - no problems! Please make sure to connect the GND of the external voltage source to the GND of the MEGA for external voltage sources.

Also with me all segments were permanently displayed. Then I took the trouble to reload all solder pads on the displayboard, including the SMD chip. This stopped the problems.

So that no doubt arise, I also use the China clones of the MEGA and the display boards come from China. I think the problem is ROHS-compliant manufacturing, which does not allow for lead. I, however, only use solder with lead. It has the advantage that the solder joints shine and not shiny solder joints are cold solder joints. However, ROHS-compliant solder produces only non-shiny solder joints. In addition, the mass production should contribute to the fact that the temperature of the solder bath drops and thereby cold solder joints.

One should be aware that the low price of the MEGA and / or the displays has its causes and it may be necessary to rework something.

But: since I've finished the parts, everything runs smoothly.

You should read the following topics please, as well as your problems are described AND how to solve them:
Which way of problem solving you go is up to you. But inform yourself, decide and then act. If then no success should set, you send me your hardware and I bring it personally to running;)
Stephan (Time: UTC+1)
2018-08-01 18:35
Posts: 41
Wonderful Stephan!

Thank you very much for the links to other having the same problem.
Have read a few of them and now I understand.
Will work on my simulator whenever there is time for me to do so and try this out. Sounds like I will find a solution.

Thank you very much for your support, as well as all others that have replied here!
You are very helpful!

2018-08-01 23:16
Posts: 41
Good day ally happy simers

Today I had the possibility to work a bit more on my problem.
Have bought cmpletely new Arduino Mega 2560 cards from a German supplier and also removed the D1 diode, replaced it with a bridge.
And all of a sudden I have no problems at all!

The problem was simply an Arduino board from China that was a problem.

Also, now there is no problem to chain displays as you here on the forum learned me. Thank you very much for that lesson!
Now I am happy and my COM1 active + standby works as it is supposed to.

The links StephanHo gave me were perfect. I have not been able to search the forum in a good way so I have not found these topics without your help. Very thankful for these links!!

Have a wonderful day you all!
This topic can now be close.
2018-08-08 16:43
From: EDDG, Germany
Posts: 1819
Hi Sebastian,

nice, if you could eliminate the mistake and be satisfied.

Continue to have fun and success building your homecockpit.
Stephan (Time: UTC+1)
2018-08-09 09:15