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incubator-nuttx/drivers/leds/ws2812.c

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/****************************************************************************
* drivers/leds/ws2812.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdlib.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
#include <nuttx/spi/spi.h>
#include <nuttx/leds/ws2812.h>
#ifdef CONFIG_WS2812
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* In order to meet the signaling timing requirements, the waveforms required
* to represent a 0/1 symbol are created by specific SPI bytes defined here.
*
* Only two target frequencies: 4 MHz and 8 MHz. However, given the tolerance
* allowed in the WS2812 timing specs, two ranges around those target
* frequencies can be used for better flexibility. Extreme frequencies
* rounded to the nearest multiple of 100 kHz which meets the specs.
* Try to avoid using the extreme frequencies.
*
* If using an LED different to the WS2812 (e.g. WS2812B) check its timing
* specs, which may vary slightly, to decide which frequency is safe to use.
*
* WS2812 specs:
* T0H range: 200ns - 500ns
* T1H range: 550ns - 850ns
* Reset: low signal >50us
*/
#if CONFIG_WS2812_FREQUENCY >= 3600000 && CONFIG_WS2812_FREQUENCY <= 5000000
# define WS2812_ZERO_BYTE 0b01000000 /* 200ns at 5 MHz, 278ns at 3.6 MHz */
# define WS2812_ONE_BYTE 0b01110000 /* 600ns at 5 MHz, 833ns at 3.6 MHz */
#elif CONFIG_WS2812_FREQUENCY >= 5900000 && CONFIG_WS2812_FREQUENCY <= 9000000
# define WS2812_ZERO_BYTE 0b01100000 /* 222ns at 9 MHz, 339ns at 5.9 MHz */
# define WS2812_ONE_BYTE 0b01111100 /* 556ns at 9 MHz, 847ns at 5.9 MHz */
#else
# error "Unsupported SPI Frequency"
#endif
/* Reset bytes
* Number of empty bytes to create the reset low pulse
* Aiming for 60 us, safely above the 50us required.
*/
#define WS2812_RST_CYCLES (CONFIG_WS2812_FREQUENCY * 60 / 1000000 / 8)
#define WS2812_BYTES_PER_LED (8 * 3)
#define WS2812_RW_PIXEL_SIZE 4
/* Transmit buffer looks like:
* [<----N reset bytes---->|<-RGBn->...<-RGB0->|<----1 reset byte---->]
*
* It is important that this is shipped as close to one chunk as possible
* in order to meet timing requirements and to keep MOSI from going high
* between transactions. Some chips will leave MOSI at the state of the
* MSB of the last byte for this reason it is recommended to shift the
* bits that represents the zero or one waveform so that the MSB is 0.
* The reset byte after the RGB data will pad the shortened low at the end.
*/
#define TXBUFF_SIZE(n) (WS2812_RST_CYCLES + n * WS2812_BYTES_PER_LED + 1)
/****************************************************************************
* Private Types
****************************************************************************/
struct ws2812_dev_s
{
FAR struct spi_dev_s *spi; /* SPI interface */
uint16_t nleds; /* Number of addressable LEDs */
uint8_t *tx_buf; /* Buffer for write transaction and state */
sem_t exclsem; /* Assures exclusive access to the driver */
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static inline void ws2812_configspi(FAR struct spi_dev_s *spi);
static void ws2812_pack(FAR uint8_t *buf, uint32_t rgb);
/* Character driver methods */
static int ws2812_open(FAR struct file *filep);
static int ws2812_close(FAR struct file *filep);
static ssize_t ws2812_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
static ssize_t ws2812_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
static off_t ws2812_seek(FAR struct file *filep, off_t offset, int whence);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_ws2812fops =
{
ws2812_open, /* open */
ws2812_close, /* close */
ws2812_read, /* read */
ws2812_write, /* write */
ws2812_seek, /* seek */
NULL, /* ioctl */
NULL, /* poll */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
NULL /* unlink */
#endif
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: ws2812_configspi
*
* Description:
* Set the SPI bus configuration
*
****************************************************************************/
static inline void ws2812_configspi(FAR struct spi_dev_s *spi)
{
/* Configure SPI for the WS2812
* There is no CS on this device we just use MOSI and it is exclusive
*/
SPI_LOCK(spi, true); /* Exclusive use of the bus */
SPI_SETMODE(spi, SPIDEV_MODE3);
SPI_SETBITS(spi, 8);
SPI_HWFEATURES(spi, 0);
SPI_SETFREQUENCY(spi, CONFIG_WS2812_FREQUENCY);
}
/****************************************************************************
* Name: ws2812_pack
*
* Description:
* This writes the expanded SPI transaction to the transaction buffer
* for a given 24bit RGB value.
*
* Input Parameters:
* buf - The location in the transmit buffer to write.
* rgb - A 24bit RGB color 8bit red, 8-bit green, 8-bit blue
*
****************************************************************************/
static void ws2812_pack(FAR uint8_t *buf, uint32_t rgb)
{
uint8_t bit_idx;
uint8_t byte_idx;
uint8_t offset = 0;
uint8_t color;
uint32_t grb;
grb = (rgb & 0x00ff00) << 8;
grb |= (rgb & 0xff0000) >> 8;
grb |= rgb & 0x0000ff;
for (byte_idx = 0; byte_idx < 3; byte_idx++)
{
color = (uint8_t)(grb >> (8 * (2 - byte_idx)));
for (bit_idx = 0; bit_idx < 8; bit_idx++)
{
if (color & (1 << (7 - bit_idx)))
{
buf[offset] = WS2812_ONE_BYTE;
}
else
{
buf[offset] = WS2812_ZERO_BYTE;
}
offset++;
}
}
}
/****************************************************************************
* Name: ws2812_open
*
* Description:
* This function is called whenever the WS2812 device is opened.
*
****************************************************************************/
static int ws2812_open(FAR struct file *filep)
{
return OK;
}
/****************************************************************************
* Name: ws2812_close
*
* Description:
* This routine is called when the WS2812 device is closed.
*
****************************************************************************/
static int ws2812_close(FAR struct file *filep)
{
return OK;
}
/****************************************************************************
* Name: ws2812_read
****************************************************************************/
static ssize_t ws2812_read(FAR struct file *filep, FAR char *buffer,
size_t buflen)
{
return -ENOSYS;
}
/****************************************************************************
* Name: ws2812_write
*
* Description:
* This routine is called when writing to the WS2812 device. Data buffer
* should be an array of 32bit values holding 24bits of color information
* in host byte ordering 0x**rrggbb.
*
****************************************************************************/
static ssize_t ws2812_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen)
{
FAR struct inode *inode = filep->f_inode;
FAR struct ws2812_dev_s *priv = inode->i_private;
FAR uint8_t *tx_pixel;
FAR uint32_t *pixel_buf = (FAR uint32_t *)buffer;
size_t cur_led;
size_t start_led;
size_t end_led;
size_t written = 0;
if (buffer == NULL)
{
lederr("ERROR: Buffer is null\n");
return -EINVAL;
}
/* We need at least one LED, so 1 byte */
if (buflen < 1)
{
lederr("ERROR: You need to control at least 1 LED!\n");
return -EINVAL;
}
if ((buflen % WS2812_RW_PIXEL_SIZE) != 0)
{
lederr("ERROR: LED values must be 24bit packed in 32bit\n");
return -EINVAL;
}
nxsem_wait(&priv->exclsem);
start_led = filep->f_pos / WS2812_RW_PIXEL_SIZE;
tx_pixel = priv->tx_buf + WS2812_RST_CYCLES + \
start_led * WS2812_BYTES_PER_LED;
end_led = start_led + (buflen / WS2812_RW_PIXEL_SIZE) - 1;
ledinfo("Start: %d End: %d\n", start_led, end_led);
if (end_led > (priv->nleds -1))
{
end_led = priv->nleds - 1;
}
for (cur_led = start_led; cur_led <= end_led; cur_led++)
{
ws2812_pack(tx_pixel, *pixel_buf & 0xffffff);
pixel_buf++;
tx_pixel += WS2812_BYTES_PER_LED;
written += WS2812_RW_PIXEL_SIZE;
}
SPI_SNDBLOCK(priv->spi, priv->tx_buf, TXBUFF_SIZE(priv->nleds));
/* Update LED position and handle case were we wrote the last LED */
filep->f_pos += written;
if (end_led == (priv->nleds - 1))
{
filep->f_pos -= WS2812_RW_PIXEL_SIZE;
}
nxsem_post(&priv->exclsem);
return written;
}
/****************************************************************************
* Name: ws2812_seek
*
* Description:
* This routine is called when seeking the WS2812 device. This can be used
* to address the starting LED to write. This should be done on a full
* color boundary which is 32bits. e.g. LED0 - offset 0, LED 8 - offset 32
*
****************************************************************************/
static off_t ws2812_seek(FAR struct file *filep, off_t offset, int whence)
{
FAR struct inode *inode = filep->f_inode;
FAR struct ws2812_dev_s *priv = inode->i_private;
off_t maxpos;
off_t pos;
if ((offset % WS2812_RW_PIXEL_SIZE) != 0)
{
return (off_t)-EINVAL;
}
nxsem_wait(&priv->exclsem);
maxpos = (priv->nleds - 1) * WS2812_RW_PIXEL_SIZE;
pos = filep->f_pos;
switch (whence)
{
case SEEK_CUR:
pos += offset;
if (pos > maxpos)
{
pos = maxpos;
}
else if (pos < 0)
{
pos = 0;
}
filep->f_pos = pos;
break;
case SEEK_SET:
pos = offset;
if (pos > maxpos)
{
pos = maxpos;
}
else if (pos < 0)
{
pos = 0;
}
filep->f_pos = pos;
break;
case SEEK_END:
pos = maxpos + offset;
if (pos > maxpos)
{
pos = maxpos;
}
else if (pos < 0)
{
pos = 0;
}
filep->f_pos = pos;
break;
default:
/* Return EINVAL if the whence argument is invalid */
pos = (off_t)-EINVAL;
break;
}
nxsem_post(&priv->exclsem);
return pos;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: ws2812_leds_register
*
* Description:
* Register the WS2812 character device as 'devpath'
*
* Input Parameters:
* devpath - The full path to the driver to register. E.g., "/dev/leds0"
* spi - An instance of the SPI interface to use to communicate with
* WS2812
* nleds - Number of addressable LEDs
*
* Returned Value:
* Zero (OK) on success; a negated errno value on failure.
*
****************************************************************************/
int ws2812_leds_register(FAR const char *devpath, FAR struct spi_dev_s *spi,
uint16_t nleds)
{
FAR struct ws2812_dev_s *priv;
int ret;
int led;
/* Initialize the WS2812 device structure */
priv = (FAR struct ws2812_dev_s *)kmm_malloc(sizeof(struct ws2812_dev_s));
if (!priv)
{
lederr("ERROR: Failed to allocate instance\n");
return -ENOMEM;
}
priv->nleds = nleds;
priv->tx_buf = (FAR uint8_t *)kmm_zalloc(TXBUFF_SIZE(priv->nleds));
if (!priv->tx_buf)
{
lederr("ERROR: Failed to allocate tx buffer\n");
kmm_free(priv);
return -ENOMEM;
}
/* Mark LED section of TX buffer as off */
for (led = 0; led < priv->nleds; led++)
{
ws2812_pack(
priv->tx_buf + WS2812_RST_CYCLES + led * WS2812_BYTES_PER_LED,
0);
}
priv->spi = spi;
ws2812_configspi(priv->spi);
nxsem_init(&priv->exclsem, 0, 1);
SPI_SNDBLOCK(priv->spi, priv->tx_buf, TXBUFF_SIZE(priv->nleds));
/* Register the character driver */
ret = register_driver(devpath, &g_ws2812fops, 0666, priv);
if (ret < 0)
{
lederr("ERROR: Failed to register driver: %d\n", ret);
kmm_free(priv->tx_buf);
kmm_free(priv);
}
return ret;
}
#endif /* CONFIG_WS2812 */
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