Make I2S compile

README.md

@@ -4,11 +4,10 @@
 
 This port of FastLED 3.3 runs under the 4.x ESP-IDF development environment. Enjoy.
 
-MASSIVE UPDATE Sept 4, 2020. Even after porting Sam Guyer's branch in July, I still
-had a huge amount of visual artifacts. I've done a huge analysis and have licked the issue to my
-satisfaction, and can say the system simply doesn't glitch.
-
-UPDATE 2 Sept 11, 2020. Added the WS2812FX pattern library, see below.
+Updates: Aug, Sept 2020: 
+- RMT interface well tested. 
+- WS2812FX library ported and working.
+- I2S hardware working ( see below )
 
 There are some new tunables, and if you're also fighting glitches, you need to read `components/FastLED-idf/ESP-IDF.md`.
 
@@ -53,6 +52,17 @@ Playing around, there are "a lot of nice libraries on FastLED", but each and eve
 requires porting. At least, now there's a single one to start with. See the underlying component,
 and use it or not. If you don't want it, just don't bring that component over into your project.
 
+# I2S vs RMT
+
+At first, I focused the port on RMT, as it seemed the hardware everyone talked about. As you see
+below, the RMT interface even has a Espressif provided example! Thus the journey of getting the MEM_BUFS
+code working and soak up the interrupt latency.
+
+But, the I2S hardware is almost certainly cooler than RMT. It has more parallelism, and less code.
+
+Right now, the code is still checked in with default RMT simply because I haven't tested I2S as much,
+but please see the I2S section below on enabling it.
+
 # TL;DR about this repo
 
 As with any ESP-IDF project, there is a sdkconfig file. It contains things that might
@@ -80,7 +90,7 @@ and using a 4-pin package isn't so cool as an 8 pin package, since an ESP32 can
 8 channels. That's SN74HCT245N , and they're to be had from Digikey at $0.60. Read the datasheet
 carefully and get the direction and the enable pins right - they can't float.
 
-# Use of ESP32 hardware (RMT) for 3 wire LEDs
+# Use of ESP32 RMT hardware for 3 wire LEDs
 
 The ESP32 has an interesting module, called RMT. It's a module that's
 meant to make arbitrary waveforms on pins, without having to bang each pin at
@@ -115,6 +125,22 @@ and if you want to use the direct mode, you should turn off the driver.
 
 No extra commands in `menuconfig` seem necessary.
 
+# Use of ESP32 I2S hardware for 3 wire LEDs
+
+## TL;DR enable it
+
+There's a `#define` at the top of fastled.h which chooses I2S or RMT. Switch to I2S.
+
+Comment out `"platforms/esp/32/clockless_rmt_esp32.cpp"` from `components\FastLED-idf\CMakeLists.txt`
+
+You need to remove the RMT file from the compile because you don't want to waste RAM, and there
+are colliding symbols. You can't use both because there's no current way to define which strings
+use which hardware.
+
+## Which to use?
+
+Not sure yet. Going to play with it on different builds and see what works.
+
 # Four wire LEDs ( APA102 and similar )
 
 Interestingly, four wire LEDs can't use the RMT interface, because