apb_target_led_ws2812

Files
file	apb_target_led_ws2812.cdl
	Simple APB target for driving a chain of Neopixels.

Detailed Description

Modules

module apb_target_led_ws2812::apb_target_led_ws2812	(	clock	clk,
		input bit	reset_n,
		input t_apb_request	apb_request,
		output t_apb_response	apb_response,
		input bit	divider_400ns_in[8],
		output bit	led_chain
	)

Parameters

[in]	clk	System clock
[in]	reset_n	Active low reset
[in]	apb_request	APB request
[out]	apb_response	APB response
[in]	divider_400ns_in	Default value for divider_400ns
[out]	led_chain	A simple module to drive a chain of Neopixel LEDs as an APB target.

The Neopixel LEDs are 24-bit RGB LEDs that are driven through a chain, with a single control pin providing the information for the LEDs.

This module supports up to 16 LEDs in a chain, each with a 24-bit RGB value. The chain must be configured with a clock divider (which is the number of clock ticks required to generate a 400ns, approximately, clock) and the number of LEDs in the chain.

The clock divider resets to 0, but whenever it is zero it resets to the input value divider_400ns_in; hence it may be effectively 'hardwired'.

Once configured the LED colors can be individually written to address-mapped registers. The LED chain automatically updates.

The configuration register is:

Bits	Meaning
12;2	zero
4;16	last LED in the chain (0 for one LED, 15 for sixteen LEDs)
8;8	zero
8;0	clock divider to create a 400ns clock enable from system clock

Example divider values

System clock | Period | Divider

50MHz | 20ns | 19 100MHz | 10ns | 39 20MHz | 50ns | 7