I am using an Arduino Uno to interface with a long string of LPD8806s via FastSPI which has been great, but now I’m trying to add an SD card reader which also requires SPI. For the heck of it I decided to try moving the typical clock and data pins for the LEDs from 11 and 13 to 5 and 7. Much to my surprise this appears to be working. Is such a configuration acceptable or is there something I’m missing that makes this poor practice?
You’ll be bit banging the spi timing instead of using the processor spi pins… It’ll cost you more cycles or more time when you can’t handle interrupts, etc
It’ll bit bang - shouldn’t be a problem with interrupts - i’ve spent a fair bit of time trying to get the bit banging support as fast as possible, while it won’t ever be as fast as hardware, i’ve gotten over 2Mbps on 16Mhz cpus, and over 6Mbps on the teensy 3. Things like this are exactly the reason why the library will transparently slide between hardware SPI and bitbang’d under the hood for you.
Next up will be abusing the USART in SPI mode for platforms that support that 
Awesome, thanks for the info! I’ll continue to test it out but initial results look extremely positive
FYI, that’s what my POV setup is like, SD reader on hardware SPI, with the strings on pins 11 and 12. Keep in mind that this is on a 32u4 AVR, which had separate pins for SPI. On a 328p, you’ll have to pick lower pins just like you did.
You should try to develop on a Micro. Much smaller than an Uno.
For various reasons I’ve actually switched to a Teensy 3.1 and it is awesome. Significantly smaller and so much more memory to play with.
Except, there’s no (official) FastLED support for the 3.1 yet … only 3.0 …
In theory, the 3.1 should work for spi (hardware and bit-banged) - but the timings appear to be off for the clockline less chips (ws2811 and neopixel and friends). I’m just holding off on calling it good until I get those chips working on there, since many people are using them.
(Also, 3.1 support will require pulling down the 2.1 branch which, right now, is only available via git/github - I’m hoping we can spin up a 2.1 preview release soon, @Mark_Kriegsman and I are going to talk later this week to finalize what we want on the 2.1 and 2.2 lists
I can attest to the fact that a 3.1 bit bangs 8806s with aplomb