PiUPShield - Looking for Input

[CaptainMurdoch]

Still curious on where this project ended up (the ability to drive 3-4 strands off a Pi).

We are using the updated version of the library in FPP v2.x, so we should be able to support the PCM and SPI outputs with some code modifications in the RPIWS281x Channel Output class and UI.  It looks like the library auto detects which mode to use by looking at the GPIO pin that you tell it to use.  Right now, we have the GPIO outputs hardcoded for 18 and 19.  If you want to test a 1-line source change, you should be able to see if the library will work with FPP as-is.  I can tell you what line to modify and the value to use to test PCM and the value to use to test SPI.  If those work individually, then I can do some more testing to see if we can run multiple PWM/PCM/SPI at the same time.  Right now we have an instance of a ws2811_t struct that we have to pass to the library to initialize it.  I don't know if the library supports multiple instances of this struct or not, that is the more complicated test.  I read through some of the commits and the README for the library, but can't find anything that says it will or won't support multiple outputs at the same time.

[Bwinter]

Once I wrap up this season, I'd definitely be interested in testing this out.

[dkulp]

If you need more than 2 strings off of an FPP instance, aren't you better off with a BBB (can run 54 strings) or PocketBeagle (36 strings)?

[Bwinter]

Well, I don't technically *need* 4-outputs, but they would be nice to have (and I would certainly use them if available).  I'm already settled in the Pi environment (I have 20+ of various models)—so I really don't want to drop those, only to stock up on something else.  And I'm comfortable enough with the nuances of them (I.e., power, audio, video, etc).

[Bwinter]

If you need more than 2 strings off of an FPP instance, aren't you better off with a BBB (can run 54 strings) or PocketBeagle (36 strings)?

I'm also honestly confused here:  if I wanted to run 36+ strings, wouldn't I be better off with a F16?  Then again, why would I settle for 16 when I could get 36 (2x the outputs at a fraction of the cost)?  Sure, the F16 has does bells-and-whistles (which I've never needed), but the numbers don't make sense (in my mind).

And this is also why I just stick to the PiHat environment—it makes sense to me...

[dkulp]

If you need more than 2 strings off of an FPP instance, aren't you better off with a BBB (can run 54 strings) or PocketBeagle (36 strings)?

I'm also honestly confused here:  if I wanted to run 36+ strings, wouldn't I be better off with a F16?  Then again, why would I settle for 16 when I could get 36 (2x the outputs at a fraction of the cost)?  Sure, the F16 has does bells-and-whistles (which I've never needed), but the numbers don't make sense (in my mind).

Kind of depends...  With an F16, you would still need e1.31 or similar to get data there.   You wouldn't need that with a BBB as it's a full FPP instance that can run in remote more.   Basically, the BBB+Cape's are EXACTLY like the Pi+Hat, just more capable.  With FPP 2.x, they are really configured exactly the same.  Same FPP image install instructions, same interface for configuring strings, etc....   

[dkulp]

I should also note that none of the capes for the BBB use the BBB to their full potential.   The F8-PB only exposes 8 ports (of the 36) directly with fuses and such.   The others are either via differential outputs (12 strings) or a 16 port expansion header.   I did create a F32-B at one point, but not many people were interested in that many strings in one spot so I didn't sell many. 

[Bwinter]

Yeah, I'm s big fan of the hat/cape concept and not needing a separate device to connect/Output e1.31.

I've developed my own 2-data/power and 2-power-injection output boards for PiZeroW, and separate boards for my icicle distribution (also based on a PiZeroW).  Sounds like I should have started going down the BBB path earlier. Too late now

[CaptainMurdoch]

We are using the updated version of the library in FPP v2.x, so we should be able to support the PCM and SPI outputs with some code modifications in the RPIWS281x Channel Output class and UI.  It looks like the library auto detects which mode to use by looking at the GPIO pin that you tell it to use.  Right now, we have the GPIO outputs hardcoded for 18 and 19.  If you want to test a 1-line source change, you should be able to see if the library will work with FPP as-is.  I can tell you what line to modify and the value to use to test PCM and the value to use to test SPI.  If those work individually, then I can do some more testing to see if we can run multiple PWM/PCM/SPI at the same time.  Right now we have an instance of a ws2811_t struct that we have to pass to the library to initialize it.  I don't know if the library supports multiple instances of this struct or not, that is the more complicated test.  I read through some of the commits and the README for the library, but can't find anything that says it will or won't support multiple outputs at the same time.

Just a follow-up on this.  I updated the rpi_ws281x.cpp Channel Output code to allow specifying the GPIO number in the co-pixelStrings.json config file.  I also updated it to allow multiple instances of the RPIWS281xOutput class for testing purposes.  I tried using the SPI output and the PWM output at the same time and I did get lights blinking when using the SPI output, but there was noticeable interference.  I compiled fppd without WiringPi support and still saw what looked like some interference when using the SPI output and the PWM outputs at the same time.  I'm not sure if this is because it is a limitation or if there is something else pinging the SPI bus that is causing the hiccups.  I pushed the code to master along with comments on how to update the co-pixelStrings.json file to test further combinations.  I also did not test on a newer B+/2B/3B/3B+, my testing was on an original v1 B, so I couldn't test the PCM output which uses GPIO 21 on pin 40.  I still think that a BBB or F4v3 are the better solution if you need 3-4 strings, but wanted to see if the additional outputs would work in FPP without a lot of effort.

[Bwinter]

Interesting....I'll play around with this