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add ws2813 timings support #510

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add ws2813 timings support #510

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6 changes: 3 additions & 3 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -28,10 +28,10 @@ to the appropriate output pin.
For SPI the Raspbian spidev driver is used (`/dev/spidev0.0`).
This library and test program set the clock rate to 3X the desired output
frequency and creates a bit pattern in RAM from an array of colors where
each bit is represented by 3 bits as follows.
each bit is represented by 4 bits as follows.

Bit 1 - 1 1 0
Bit 0 - 1 0 0
Bit 1 - 1 1 1 0
Bit 0 - 1 0 0 0


### GPIO Usage:
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32 changes: 17 additions & 15 deletions ws2811.c
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Expand Up @@ -58,11 +58,21 @@
#define OSC_FREQ 19200000 // crystal frequency
#define OSC_FREQ_PI4 54000000 // Pi 4 crystal frequency

// Symbol definitions
#define SYMBOL_HIGH 0b1110
#define SYMBOL_LOW 0b1000

// Symbol definitions for software inversion (PCM and SPI only)
#define SYMBOL_HIGH_INV 0b0001
#define SYMBOL_LOW_INV 0b0111

#define SYMBOL_LEN ((int)log2(SYMBOL_HIGH)+1)

/* 4 colors (R, G, B + W), 8 bits per byte, 3 symbols per bit + 55uS low for reset signal */
#define LED_COLOURS 4
#define LED_RESET_uS 55
#define LED_BIT_COUNT(leds, freq) ((leds * LED_COLOURS * 8 * 3) + ((LED_RESET_uS * \
(freq * 3)) / 1000000))
#define LED_RESET_uS SYMBOL_LEN == 3 ? 55 : 300
#define LED_BIT_COUNT(leds, freq) ((leds * LED_COLOURS * 8 * SYMBOL_LEN) + ((LED_RESET_uS * \
(freq * SYMBOL_LEN)) / 1000000))

/* Minimum time to wait for reset to occur in microseconds. */
#define LED_RESET_WAIT_TIME 300
Expand All @@ -72,14 +82,6 @@
RPI_PWM_CHANNELS)
#define PCM_BYTE_COUNT(leds, freq) ((((LED_BIT_COUNT(leds, freq) >> 3) & ~0x7) + 4) + 4)

// Symbol definitions
#define SYMBOL_HIGH 0x6 // 1 1 0
#define SYMBOL_LOW 0x4 // 1 0 0

// Symbol definitions for software inversion (PCM and SPI only)
#define SYMBOL_HIGH_INV 0x1 // 0 0 1
#define SYMBOL_LOW_INV 0x3 // 0 1 1

// Driver mode definitions
#define NONE 0
#define PWM 1
Expand Down Expand Up @@ -359,7 +361,7 @@ static int setup_pwm(ws2811_t *ws2811)
stop_pwm(ws2811);

// Setup the Clock - Use OSC @ 19.2Mhz w/ 3 clocks/tick
cm_clk->div = CM_CLK_DIV_PASSWD | CM_CLK_DIV_DIVI(osc_freq / (3 * freq));
cm_clk->div = CM_CLK_DIV_PASSWD | CM_CLK_DIV_DIVI(osc_freq / (SYMBOL_LEN * freq));
cm_clk->ctl = CM_CLK_CTL_PASSWD | CM_CLK_CTL_SRC_OSC;
cm_clk->ctl = CM_CLK_CTL_PASSWD | CM_CLK_CTL_SRC_OSC | CM_CLK_CTL_ENAB;
usleep(10);
Expand Down Expand Up @@ -442,7 +444,7 @@ static int setup_pcm(ws2811_t *ws2811)
stop_pcm(ws2811);

// Setup the PCM Clock - Use OSC @ 19.2Mhz w/ 3 clocks/tick
cm_clk->div = CM_CLK_DIV_PASSWD | CM_CLK_DIV_DIVI(osc_freq / (3 * freq));
cm_clk->div = CM_CLK_DIV_PASSWD | CM_CLK_DIV_DIVI(osc_freq / (SYMBOL_LEN * freq));
cm_clk->ctl = CM_CLK_CTL_PASSWD | CM_CLK_CTL_SRC_OSC;
cm_clk->ctl = CM_CLK_CTL_PASSWD | CM_CLK_CTL_SRC_OSC | CM_CLK_CTL_ENAB;
usleep(10);
Expand Down Expand Up @@ -1196,7 +1198,7 @@ ws2811_return_t ws2811_render(ws2811_t *ws2811)
if ((driver_mode != PWM) && channel->invert) symbol = SYMBOL_HIGH_INV;
}

for (l = 2; l >= 0; l--) // Symbol
for (l = SYMBOL_LEN; l >= 0; l--) // Symbol
{
uint32_t *wordptr = &((uint32_t *)pxl_raw)[wordpos]; // PWM & PCM
volatile uint8_t *byteptr = &pxl_raw[bytepos]; // SPI
Expand Down Expand Up @@ -1229,7 +1231,7 @@ ws2811_return_t ws2811_render(ws2811_t *ws2811)
else // PWM & PCM
{
// Every other word is on the same channel for PWM
wordpos += (driver_mode == PWM ? 2 : 1);
wordpos += (driver_mode == PWM ? RPI_PWM_CHANNELS : 1);
bitpos = 31;
}
}
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