Hey FastLED community!
I’m just about to dive into a portable POV project that will be utilizing 2x 36 LED strips of apa102 leds and a 32u4 micro w/ microSD shield.
I was wondering if anyone has any experience running softSPI to drive APAs in conjunction with hardware SPI to a microSD shield? (ex: Read a small portion of an array, FastLED softspi bitbang to apas and resume from last seen SDcard array position).
From what I’ve read it looks like the only successes have been through storing an entire array to RAM from SD and then switching to hard SPI to drive the APAs. Am I missing any obvious impossibility with communicating with the shield through hard SPI and then softSPI driving the LEDs? I’m guessing there would be far too slow update speeds between the two peripherals to get any POV-effective refresh rate?
I would really appreciate any insight! 
Been there, done that. I used the hardware SPI for the SD card, and bitbanged the strips. No issues. Since you have a(n) LED array, you can read data directly into that. I have 48 LEDs, so I read in exactly 144 bytes (48 x 3 for R, G, and B) into the array and push it out with .show(). The SD .read() function leaves the pointer where it last read, so you don’t have to worry about keeping track of it except for checking whether it reached the end of the file and cycle back to the top.
I took some pictures when I was spinning the last prototype I built: https://photos.google.com/share/AF1QipPYsFHysv4ul0-W1uGvmogYI4vyoQV8BvWbcLOQyhmGKUnFvWVgrM3EunRIBfAadQ?key=WnVzMVNGampHaFRBU19pbWFJSUJoXzd3TThQcHRB
I’d like to try this as well. Do you have any code sample you would be willing to share?
@Ashley_M_Kirchner_No
Those look awesome! Thanks so much for the affirmation
Now I’m really jazzed up about this project!
Yup. I figured out a lot of code pieces with the help of Daniel too. Things like reading directly into the LEDS array and not use an intermediary buffer. In the end, with the various pieces I have in play, it came down to shrinking the code to fit. Add it stands right now, it works great, but the controller needs revisiting. Then I have ideas of incorporating more hardware, such as detecting how fast one is spinning and adjust the refresh rate accordingly, so one can display a “static” image regardless of how fast or slow its spinning. The controller is already pretty packed. If I get some time today, I’ll whip up a run-time flow of what all the code does.
Check your hangouts @Michael_Langevin . Meant to send you a link but I hit enter too soon. Anyway, in its simple form, this is what my code does: https://photos.google.com/share/AF1QipPiCrrPtS8AHRpVX0-PMc6fGSw2DDWON4wz2NXDGmSv0ReIhZda0y8QcXOxjvTiuA?key=elgyYnZnSmVDSUk4bi1aQ0thalhpTlpRTWxSaWVB
I say simple because there’s a lot more going on, interrupt triggers, distinct button presses, brightness control, error codes, etc., etc.
Can you share the code you used? Ive been wanting to make a POV display for my bro’s bike using a single strip of LEDs
Honestly, I am way more likely to help you with your code than I am simply giving you mine.
Also, unless you have the identical, custom made controller that I made, my code won’t work. The flow chart above is a really good starting point.
@Ashley_M_Kirchner_No lol i love custom controllers still tweaking my Attiny85 controllers. Gonna move on to Atmega32u4’s soon. Still getting that first PCB ready. But thanx for sharing that Flow Chart
When I say controller, I’m not referring to just the microcontroller. I’m referring to the POV controller itself. Two tiny PCBs packed with over 100 tiny SMD components, fitted inside a 1" tube with the software controlling all aspects of it.
Yeah thats way above where im at. Still at noob level here lol
At the top is the test rig I was using, at the bottom is one of the first prototypes. Those two boards would stack one on top of the other. Even the LED strips are custom made. At the time, I was using LPD8806 chipsets because they were the fastest on the block then. Eventually the APA102 came out and I started using those.
@Ashley_M_Kirchner_No Das Blinken MagikStick! Love it lol. Thanx for the info. Believe it or not its been very very helpful sucks having a low budget and buying from china everything takes forever. Ugh…
