FastLED Parallel RGB_LED strips on ESP32

For a future build of we plan to control more than one LED “trail” from the host controllers

We have 6 of the Heltec Wireless Stick Lite LoRa ESP boards. These seem to have loaded up a lot of the ESP32 pins, which is one reason I started researching virtual pin multiplexing

If you want to drive many (i.e. > 8) LED strips in parallel, you will need to multiplex the pins on a “normal” ESP32. This will require some ICs, and a specific extra driver.

NeoPixels receive data from a fixed-frequency 800 KHz datastream (except for “V1” Flora pixels, which use 400 KHz).

After the last pixel’s worth of data is issued, the stream must stop for at least 50 microseconds for the new colors to “latch.”

74HC595 : this is an 8 bit shift register (you will need one 74HC595 for each Virtual pin)

That’s only the time needed to push the bits down the wire.

One pixel requires 24 bits (8 bits each for red, green blue) — 30 microseconds.

Reality in some cases could fall an order of magnitude (or more) below this.

Each bit of data therefore requires 1/800,000 sec — 1.25 microseconds.

The actual refresh rate will be something less than this, and can’t be estimated as a single number for all cases.

74HC245 : this is a bus used as a level shifter (you will need only one of them for LATCH and CLOCK)

For a strip of 100 pixels, that’s (100 * 30) + 50, or 3,050 microseconds. 1,000,000 / 3,050 = 328 updates per second, approximately.

This library is a new take on driving ws2812 leds with I2S on an esp32. It allows to drive up to 120 strips !!! leds in parallel of

It takes time to process each “frame” of animation.

The formula above gives a maximum theoretical rate, but that’s just a starting point.

How much time depends on the complexity of the math and the efficiency of the code (for example, floating-point calculations can be relatively slow).

If you are using RGB led type then this library is fully compatible with fastLED library objects

Master Sorcerer u/Yves-bazin revealed the ancient words. Before summoning your illumimatrix, the prudent photomancer must dispel unwanted darkness-daemons by loudly announcing #define FASTLED_ESP32_I2S true at the very top of their incantation.

The other spell is #define FASTLED_RMT_MAX_CHANNELS XXXXX, with more information found in the wonderfully illustrated Tome of ESP.

Analog Output Pins 2 (25, 26)

Analog Input Pins 6 (VP, VN, 32, 33, 34, 35)

To enable the I2S driver, add the following line before including FastLED.h (no other changes are necessary):

#define FASTLED_ESP32_I2S true

* Unlike the RMT peripheral the I2S system cannot send bits of * different lengths. Instead, we set the I2S data clock fairly high * and then encode a signal as a series of bits.

* The overall strategy is to use the parallel mode of the I2S “audio”

* peripheral to send up to 24 bits in parallel to 24 different pins.

1111111000 WS2812 "1" bit encoded as 10 125ns pulses

The implementation uses two DMA buffers by default. To increase the number of DMA buffers set the preprocessor definition

FASTLED_ESP32_I2S_NUM_DMA_BUFFERS

to a value between 2 and 16. Increasing the buffer to 4 by adding

#define FASTLED_ESP32_I2S_NUM_DMA_BUFFERS 4

solves flicker issues in combination with interrupts triggered by other code parts.