Document WS2812B level shifter erratum

README.MD

@@ -12,3 +12,7 @@ Board to run [colorchord2](https://github.com/cnlohr/colorchord) on a string of
 	* Workaround: Flip 180 degrees and solder shifted onto the right pads, then use magnet wire to connect the remaining two pads.
 * Serial boot loader non-functional (uses incompatible UART I/Os).
 	* Workaround: Program via JTAG / SWD.
+* Missing level shifters for WS2812B LEDs (RX)
+	* Workaround: Don't use WS2812B RX inputs on the board
+* Missing level shifters for WS2812B LEDs (TX)
+	* Workaround: The first LED will kinda sorta do the level shifting for you, but sometimes fail to display correctly. Just ignore its erratic blinking.

firmware/ccconfig.h

@@ -2,8 +2,8 @@
 #define _CCCONFIG_H
 
 #define CCEMBEDDED
-#define NUM_LIN_LEDS 66
-#define USE_NUM_LIN_LEDS NUM_LIN_LEDS
+#define NUM_LIN_LEDS 60
+#define USE_NUM_LIN_LEDS 60
 #define DFREQ (40000)
 
 #endif

firmware/main.c

@@ -179,7 +179,7 @@ int main(void)
 			this_samp = (this_samp+1)%CIRCBUFSIZE;
 
 			wf++;
-			if( wf == 128 * 2)
+			if( wf == 128 )
 			{
 				NewFrame();
 				wf = 0; 

firmware/spi2812.c

@@ -282,14 +282,13 @@ void SendSPI2812( unsigned char * lightarray, int length )
 	static const uint8_t aoarray[4] = { 0b10001000, 0b10001110, 0b11101000, 0b11101110 };
 
 	int i;
-	int subdiv = 0;
-	uint8_t * buffbase = &MyBuffer[ZERO_BUFFER];
+	if( length > SPI2812_MAX_LEDS ) length = SPI2812_MAX_LEDS;
 
-	if( length * SPI2812_LED_SCALING > SPI2812_MAX_LEDS ) length = SPI2812_MAX_LEDS;
-
-	for( i = 0; i < length;)
+	MyBuffer[0] = 0;
+	for( i = 0; i < length; i++ )
 	{
 		uint8_t * colorbase = &lightarray[i*3];
+		uint8_t * buffbase = &MyBuffer[i*24/2+ZERO_BUFFER];
 
 		int j;
 		for( j = 0; j < 3; j++ )
@@ -301,17 +300,11 @@ void SendSPI2812( unsigned char * lightarray, int length )
 			*(buffbase++) = aoarray[(c>>2)&3];
 			*(buffbase++) = aoarray[(c>>0)&3];
 		}
-
-		if (++subdiv == SPI2812_LED_SCALING) {
-			subdiv = 0;
-			i++;
-		}
 	}
 
 	for( i = 0; i < ZERO_BUFFER; i++ )
 		MyBuffer[i] = 0;
 
-	length *= SPI2812_LED_SCALING;
 	length *= 24/2;
 	length += ZERO_BUFFER;
 

firmware/spi2812.h

@@ -6,7 +6,6 @@
 //24 bits per LED, can fit two bits per byte of output.
 #define SPI2812_BUFFSIZE (SPI2812_MAX_LEDS*24/2)
 
-#define SPI2812_LED_SCALING 3
 
 void InitSPI2812();
 void SendSPI2812( unsigned char * lightarray, int leds ); //Need one R, G, B per element.