MobiFlight Community Support

Hi there,

i've read some threads here including https://www.mobiflight.com/forum/message/11517.html but i'm still not sure whether i got it right.

For your ease i ask some questions, which can be answered via Yes or No (hopefully).

1) MF with Arduino can address 8 MAX, correct?
2) If more are needed i need an additional Arduino Mega, correct?
3) ALL MAXes must be daisy chained to be addressable, correct?
4) Assume i have one display with 5 digits and one with 3, it would be easy to address them with one single MAX, but e.g. for two 5 Digit displays it will be difficult (or almost impossible) to address them like: Display A on MAX A, 3 digits from Display B on MAX A and 2 digits on MAX B.
Here it would be better to spend one MAX for each 5 (or 6) digit Display and to use the "remaining" digits of the MAX for displays with not more than the "free ones". Correct?

I assume if i build (or plan to build) following modules:
- Rudder Trim - 4 digits
- IAS - 3 digits
- HDG - 3 digits
- ALT - 5 digits
- VS - 4 digits
- NAV Active and StdBy - each 6 digits

Then spreading all these displays without seperating them over more than one MAX this means eg.:
- MAX A: Rudder Trim and IAS
- MAX B: HDG and ALT
- MAX C: VS (with some spare digits)
- MAX D: NAV Active
- MAX E: NAV StdBy
And there are connections between MAX A to B to C to D to E (over DOUT and DIN).
Correct?

So, when building the first module i must consider to connect it to the next module, which will be build some months later. Correct?

Gentlemen, i know, heavy stuff, but i would be more then happy, if all of the bold "correct" could be answered with yes, what would mean, i finaly got it.

Thanks in advance for your attention and reading this....well....beginners knot in the brain.

Kai

Multiple questions.... Multiple awnsers..... lets split them up !

1) MF with Arduino can address 8 MAX, correct?

NO! ..... Mf itself can adress thousonds of MAX..... the Limit is on ONE Mega.....
A Mega can handle FOUR Max7219 Devices ...... And each "Device" can be a single Chip OR a Chain of multiple Chips...... Up to 8.
So.... One Mega can handle a maximum of 32 Max Chips ( 4 Devices.... And each as a chain up to 8 Chips)

Lets say you need 5 Chips..... You can set it as a Chain of 5 on a Mega ( 3 Pins) .... You can set it also as a 3 Chip Chain and a 2 Chip Chain (2 Device 6 Pins) ..... Or extremly you can say 4 Devices..... 3 Singles and one Chain of 2 Chips (12 Pins) ..... Your Choice !


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2) If more are needed i need an additional Arduino Mega, correct?

NO.... More then 8.... No prob in case a Single Mega can handle 32 Max as i explane oin (1) ...... But for Sure.... More then 32 ( or more then 4 Devices better said) THEN you need a additional Mega !

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3) ALL MAXes must be daisy chained to be addressable, correct?

NO... aA Max work as a single device.... If you need e.g. just 4 Chips and you feel ok to use 12 Pins ( 3 each) for this.... then you can wire them as single devices and NO Chain is needed...... But for sure.... If you need 5 or more Chips on ONE Mega..... Then you need one ( or more) chains..... In case the Limit of "Max Devices" is 4 .... So all more then 4 must be chained to be possible. If you not like Chains..... then Additional Megas is the key.....
Lets say you need 20 Max Chips..... Use 5 Megas.... Each with 4 Chips. Then all would be single.... without Chains !

******

4) Assume i have one display with 5 digits and one with 3, it would be easy to address them with one single MAX, but e.g. for two 5 Digit displays it will be difficult (or almost impossible) to address them like: Display A on MAX A, 3 digits from Display B on MAX A and 2 digits on MAX B.
Here it would be better to spend one MAX for each 5 (or 6) digit Display and to use the "remaining" digits of the MAX for displays with not more than the "free ones". Correct?

You can not build a Config that work on two Max Chips SAME TIME .... So its not possible to build ONE Config that show e.g "12345" and you split it over 2 Max Chips.
What you can do ( to save Max chips) is to build 2 Configs..... On controll e.g. Diggit 7 and 8 of Max1 and show "12" and the other Config controll Digit 1,2,3 of Max2 and show "345".
BUT
This is not really profitable. A MAx Chip from china cost less then 1$ ..... So why go a difficult way ?
Also if a Display need 2x4 Display.... I personlay not split the on one MAX ( whatever easy possible in MF) i simply say.... One MAX = One Display ( whatever 3,4,5,or 6 Diggit) and one Config that Controll it...... One pair of Wires ( in case i also not Chain them) .

Extreme Example ( only for my opinion)..... if i would need 20 Displays of 3 Diggits.... I would use 20 Max Chips..... and i would use 5 Megas with 4 Devices ( 12 Pins each).
For sure... All can be done also with 1 Mega and only 3 Pins on it.... 3 Diggits *20 = 60 Diggits Overall.... Can be done with 60/8=7,xxx So 1 Chain with 8 Chips. is enough!
But as i said... No individual Device Names.... Difficult Configs.... Possible Issues in the Chain.....
I would simply invest 30-50€ for the additional 12 Chips and 4 Megas and be happy !

This last question is Philosophyc..... For me a tidy system is the most important target.... Clear Logic.... Clear names. clear system !
I not care about if i need 10 MAx Chips more, 3 Megas more and spent 30$ more. For me is important all is clean and easy.

If you accept to make difficult configs.... And you like to have chains that get broke if one of the xx Max Chips got a issue..... Use. it.
For me this is no option !

Good Morning.

Thank you very very much pizman82.

Your answer is very helpful to me, now i got it.

Of course you're right, it's "nicer" to build it easy and clean, as you can buy 10 MAX for 12€ at Ali including tax, customs, shipping.

I now know that i will design my parts following the easy rule: one display - one chip (well in most cases)

Again, many thanks

Kai

To say a last thing here.... In case pretty sure some guys get scarred why i tell this.....

For fully hand wired systems my recomendation is what i think..... But if we talk about "PCB" based Systems..... Then the Situation is a little different !

We currently work ( as said in other topic) on our own PCB/Max7219/Display System.....
Means we create PCB´s for Displays ( 3,4,5,6 Diggits) ..... And we create " Max Central Boards" ( 4 Max in a Chain.... with a optional Connector to enlarge for a 8 Chip Chain by connect a second "Max Center Board" onto the other.

Here there is no wirework from Max to Max ( instead of the Tubes we need to connect together) .... All is done on the PCB. We also not need to bypass 5V to every board ( like on Tubes) .... Again all is done on the PCB. ...... So just a 5 Wire Connector on the end to a Mega ( 3 Pins,5v,GRD) .

For Display Combination we build 2 Connectors to every Max Position..... So 3-3, 3-4, 3-5, 3,4,5,6, is Possible.

For sure.... In this "perfect" PCB based system i also use Chains..... And i also set a 3 and a 5 Diggit Display together to one Max.
The only Disadvantage to the "1 Display,OneChip logic" is.... All Devices got the same Name.... So you must know what Display is set to what Chip in the Chain!
BUT
In case there are no wires anymore and all is electrical 100% Perfect..... Here i agree to work with Chains and combinded Displays!

That sounds very nice!

But what do you mean with "We currently work"? Is there a planned date for availability?

My plans are still only plans and due to some other unimportant things like work, wife, dog, kids.....i even don't think that i'm going to start into building this year.

Kai

One short question.

Are the e.g. 4 Digit LED Blocks pin-compatible, regardless of the manufacturer?

Otherwise everybody must buy exactly the same modules you designed the PCB for....

Ah...ok....second question:

Could it be (fingers crossed) that you designed the PCB etc mit KiCad? Then could it be, too, that you have the parts designed for 3, 5, 6 Digit modules?
I searched the Internet including the KiCad Forum but there is nothing to find.

Thanks

Kai

Again.... Multiple Questiosn Multiple Awnsers

That sounds very nice!
But what do you mean with "We currently work"? Is there a planned date for availability?

We designed and build the first batch..... And currently we start mounting them for our own usage. The target is.... We want to see if they are designed in a good way.
So we still order only stuff for maybe 10-20 MCP´s or radios ( The smalles ammount of Parts in China, in case 1 PCB cost same like 5 (Minimum order).... So we have them for now.
For example we still explore a Problem..... The "Cuting" of the PCB´s is to difficult ( in case we build to many holding Points in the Frame) .... So it work but need a lot of "manpower" and a power cutter or PCB Cutter tool..... So in the next Build we pretty sure redesign this.

And NOTE: We currently not be sure if we like to "sell" this or if we simply puplish the raw files.... May we also do this in cooperation with Hispapanels.... BUT: Your from Germany ( low shipping costs)..... If you like we can talk via Discord and i can send you a "testing pack" for the self costs.

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Are the e.g. 4 Digit LED Blocks pin-compatible, regardless of the manufacturer?
Otherwise everybody must buy exactly the same modules you designed the PCB for....

Thats exactly the Problem!
Our Target was.... We like a Way that all needed Displays ( 3,4,5,6) are available in the same Optic, size, Color, Font and Brightness. So simply buy a premade 3,4,5,6 Block is not possible..... We search for many hours.... But we not find them.... Also Parts from same Manifactur e.g. have a different optic in e.g. a 4 and a 5 Display (angle, thickness and so on)
So we planed for 1 Diggit Displays..... But also THIS was a mess in case One Diggit are extremly expensive ! ( And also a extreme Solder work is needed..... 60 Solder points for a 6 Diggit Display) . Whatever lots of Professional Manifacture use 1 Diggit.... We finaly decide to work with 2 and 3 !
Those was Cheap and we found a shop that have these two kinds 100% identical in Optics !

So.... The big deal in this porject is : We not only create the PCB´s.... we also need to plan for Parts that can be simply bought from all over the world for a cheap price.
For sure in Germany´s Amazon there is maybe a verry cheap 5 Diggit Display..... But Hwo should a Guy from Brasil order this.... So CHINA was our Main target ( deliver all overt the world).

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Could it be (fingers crossed) that you designed the PCB etc mit KiCad? Then could it be, too, that you have the parts designed for 3, 5, 6 Digit modules?
I searched the Internet including the KiCad Forum but there is nothing to find.

YES. Stephan do this Via KiCad.... And NO. As i know he not puplish this in case we think about comercial usage on the side.

**********

Please Joind Discord and contact me ( or better Stephan himself)
We can show you the Parts.... We can talk and awnser your questions.... And for sure you can get one for testing if you like !

Some days ago my order from Ali arrived (Maxen, 1,3,5,6 Digit displays) and i started to test all of them, first with a pretty small Arduino program (just counting from 0 to.....and showing the number on the display)

I know, following question is not really MF-related, but here are more people with experience in using the Max.

It might be that the Max is really bitchy regarding power connection, isn't it?

Connected to the PC or even a 2A-USB-Powersupply my program starts counting and latest at number 8 the display goed dark. The LED on the mega (and a serial output) shows, that the program is still running.
But when connecting the Mega with Max and Displays to my laboratory power supply with exactly 5V it runs smoothly and the current display shows max 160mA, so it couldn't be a collapsing power.

Any ideas what this can be?

Of course, when building the many modules with displays i will spend a dedicated switching power supply for all the displays, but i want understand what this strange behaviour could be with only on 4-Digit Display. The amount of digits make no difference as the Max is a multiplexer, so max 8 segments must be supported each ms.

Thanks

Kai

Make no sense....

As you say.... Max7219 normaly can not occure in a Power Problem. Stephan got 10+ Max Chips on one Mega.... Just USB Power.
In case of Multiplexing the Power usage is not really relevant !

The strange point.... If it work with external Power to the Max..... But not work with Max Powerd by the Mega..... And we pretty sure know there can not be a Power Problem overall....
Then there must be a Electrical Problem on the Mega or in the wire work.

1. Confirm you use 5V on the Mega..... Not the 3,5V by misstake.

May use a Multimeter and check the electrical power on the 5V Pin.... Check the power usage.
This sounds like a Issue.... Not like a Bug.

2. Confirm the same Problem also happen with Mobiflight..... I not know how your Library work and how the Pins are set by the "original Sketches".
So.... Flash Firmware.... Set your Max in MF .... And then Test your Displays by using a Empty Config file and just create a Output Config and use the TEST Button in Display Tab.

Hello,

i got it sorted out.

First for clarification:
The problem occured when the MEGA was powered via USB, but was gone with external Power from a lab Power Supply.
The Max was always powered from the MEGA.

However:
i googled (again) a lot and there must be some differences in the MAX family. I got MAX7219NGC (for what ever NGC stands for, i assume Next Generation Chaos...).

In zillions of schemas i saw the "normal" Max plain connected to Arduino and displays without anything else. Working fine.

But then i found In one (!) schema yesterday there are two capacitors attached to V++ and GND.
One polarised to cover short term power variability and one non-polarised to cut off unwanted peaks. Guess what? This damn thing is working now.

After another session on page two and three of the google search results (almost the dark web) i found the official spec paper of the NGS in englisch and here stands clearly, that these "capacitors must not be omitted" as otherwise problems (like mine) could occur.

Well, now i'm happy.

Hi,

LoungePilot already have MAX Display systems ready to go. 3,4,5 and 6 digits. We also have a centralised board dedicated to driving MAX displays with MEGA onboard. You can have compact all in one modules in all digit/colour variations. You can have the same with a ribbon connector also, or you can have displays that are connected back to a MAX tube with an FFC cable. We will update our website later today with all the products ready to go.

Thanks!

Let's make that update will be ready Jan 2nd! Holiday season!..

Wow, that's great news!

But as far as i know there are some different modules reg. the pin layout out there.

Could you place a table or pic or anything else how the pins must be, as i have some 3,4,5,6 digit display blocks already here. And some Maxes as well, so buying only the pcb would be great.

Thanks in advance and (a little early) a happy new year.

Kai

Hi Kai,

Happy New Year! I am struggling to find a way to get an image to upload here ok. If you shoot me an email via our site I will respond back with the info you need. Pretty sure what you have will work with our modules as long as you have common cathode.

Many thanks,
Kev.

Hi,

the letters after MAX7219/MAX7221 have the following meaning (see datasheet Maxim Integrated for MAX7219/7221 page 1 + 14)

Code:

PART                  TEMP RANGE  PIN-PACKAGE
MAX7219CNG    0°C to +70°C    24 Narrow Plastic DIP
MAX7219CWG   0°C to +70°C    24 Wide SO
MAX7219C/D      0°C to +70°C    Dice*
MAX7219ENG   -40°C to +85°C   24 Narrow Plastic DIP
MAX7219EWG  -40°C to +85°C   24 Wide SO
MAX7219ERG   -40°C to +85°C   24 Narrow CERDIP

*Dice are specified at TA= +25°C
SO = SMD

So the letters are for the temperature range and the housing. Technical all are identical.
The MAX7221 is compatible with SPI, QSPI and MICROWIR, and has slew-rate-limited segment drivers to reduce EMI.