Hi,
Might be beneficial to put a note in the API to that effect.
Keith
Hi,
Interesting results and nice to see some testing and observations from various parties Tom.tomlithgow wrote: ↑Thu Jan 06, 2022 6:36 pm Just to be controversial...I have been away from flight simming and developing AM hardware instruments for almost a year, having packed everything away for moving house in March last year.
The first instrument(s) I developed when I started making AM hardware, in 2020 was a Nav/Com unit. I had four daisy-chained pairs of MAX7219 displays running off a single Arduino Mega back then. This was using v3. Having set this up now with v4 the second displays don't function. I have tried a different Arduino and different displays and no joy.
The only thing that has changed in this setup is the software so I challenge the claim by AM that it is not a software issue.
Hi Tom, it would most likely be due to timing of the input signal (as in glitches) as the display address data for the display to be used to be processed is contained in the DataStream.tomlithgow wrote: ↑Fri Jan 07, 2022 8:47 am I'm not sure I see why one display works, and daisy chaining doesn't....unless you add capacitors to the setup. That said, I've ordered some capacitors.
Hi @Corjan Many thanks for the info.Corjan wrote: ↑Fri Jan 07, 2022 9:40 am Hi,
The software has changed quite a bit between V3 and V4. Nothing that should effect signal integrity though.
In V3, data from AM was pushed to the MAX chip directly. With V4, characters are stored in RAM on the Arduino.
That allows to combine mulitple character changes in one swoop, where all (up to 4) displays can be updated in one go.
This might have some side effects. But the actual signal generation never changed,
Corjan
Hi Keith, I am absolutely fine with that. I just want to know WHY and what the variables are. Testing a suitably long chain with these 'cheap' - sold in their millions - boards and the right test equipment should give us some useful answers.Keith Baxter wrote: ↑Fri Jan 07, 2022 10:18 am Hi,
There are peeps driving 5 MAX7219 with the cap added. However they mod their boards to drive ONE 3 digit GREEN led.
This is mainly for the electrical panel on the 737 overhead,
So unless @Corjan changed something since beta (29) then 5 displays seem to work OK.
Suppose SI are playing safe when they say only 4 can be daisy chained. Understandable as the most popular instrument is the NAV/COM radio.
Keith
Hi,Corjan wrote: ↑Fri Jan 07, 2022 2:58 pm Hi,
Since the Arduino now has to buffer all characters internally, I decided to limit it to 4. There is not much RAM to play with on some microcontrollers, every byte count.
Also, the protocol becomes slower and slower with the number of MAX chips you use. If you want to reach the last chip, you have to push dummy data though all in the chain.
You can create mulitple chains (there is no restriction there), so that would be the way to drive a many MAX chips.
Corjan