/* * Copyright (c) 2022 Jonathan Rico * * Adapted from the SPI driver, using the procedure in this blog post: * https://electronut.in/nrf52-i2s-ws2812/ * * Note: the word "word" refers to a 32-bit integer unless otherwise stated. * * WS/LRCK frequency: * This refers to the "I2S word or channel select" clock. * The I2S peripheral sends two 16-bit channel values for each clock period. * A single LED color (8 data bits) will take up one 32-bit word or one LRCK * period. This means a standard RGB led will take 3 LRCK periods to transmit. * * SPDX-License-Identifier: Apache-2.0 */ #define DT_DRV_COMPAT worldsemi_ws2812_i2s #include #define LOG_LEVEL CONFIG_LED_STRIP_LOG_LEVEL #include LOG_MODULE_REGISTER(ws2812_i2s); #include #include #include #include #include #define WS2812_I2S_PRE_DELAY_WORDS 1 struct ws2812_i2s_cfg { struct device const *dev; size_t tx_buf_bytes; struct k_mem_slab *mem_slab; uint8_t num_colors; size_t length; const uint8_t *color_mapping; uint16_t reset_words; uint32_t lrck_period; uint32_t extra_wait_time_us; bool active_low; uint8_t nibble_one; uint8_t nibble_zero; }; /* Serialize an 8-bit color channel value into two 16-bit I2S values (or 1 32-bit * word). */ static inline uint32_t ws2812_i2s_ser(uint8_t color, const uint8_t sym_one, const uint8_t sym_zero) { uint32_t word = 0; for (uint_fast8_t mask = 0x80; mask != 0; mask >>= 1) { word <<= 4; word |= (color & mask) ? sym_one : sym_zero; } /* Swap the two I2S values due to the (audio) channel TX order. */ return (word >> 16) | (word << 16); } static int ws2812_strip_update_rgb(const struct device *dev, struct led_rgb *pixels, size_t num_pixels) { const struct ws2812_i2s_cfg *cfg = dev->config; const uint8_t sym_one = cfg->nibble_one; const uint8_t sym_zero = cfg->nibble_zero; const uint32_t reset_word = cfg->active_low ? ~0 : 0; uint32_t *tx_buf; uint32_t flush_time_us; void *mem_block; int ret; /* Acquire memory for the I2S payload. */ ret = k_mem_slab_alloc(cfg->mem_slab, &mem_block, K_SECONDS(10)); if (ret < 0) { LOG_ERR("Unable to allocate mem slab for TX (err %d)", ret); return -ENOMEM; } tx_buf = (uint32_t *)mem_block; /* Add a pre-data reset, so the first pixel isn't skipped by the strip. */ for (uint16_t i = 0; i < WS2812_I2S_PRE_DELAY_WORDS; i++) { *tx_buf = reset_word; tx_buf++; } /* * Convert pixel data into I2S frames. Each frame has pixel data * in color mapping on-wire format (e.g. GRB, GRBW, RGB, etc). */ for (uint16_t i = 0; i < num_pixels; i++) { for (uint16_t j = 0; j < cfg->num_colors; j++) { uint8_t pixel; switch (cfg->color_mapping[j]) { /* White channel is not supported by LED strip API. */ case LED_COLOR_ID_WHITE: pixel = 0; break; case LED_COLOR_ID_RED: pixel = pixels[i].r; break; case LED_COLOR_ID_GREEN: pixel = pixels[i].g; break; case LED_COLOR_ID_BLUE: pixel = pixels[i].b; break; default: return -EINVAL; } *tx_buf = ws2812_i2s_ser(pixel, sym_one, sym_zero) ^ reset_word; tx_buf++; } } for (uint16_t i = 0; i < cfg->reset_words; i++) { *tx_buf = reset_word; tx_buf++; } /* Flush the buffer on the wire. */ ret = i2s_write(cfg->dev, mem_block, cfg->tx_buf_bytes); if (ret < 0) { k_mem_slab_free(cfg->mem_slab, mem_block); LOG_ERR("Failed to write data: %d", ret); return ret; } ret = i2s_trigger(cfg->dev, I2S_DIR_TX, I2S_TRIGGER_START); if (ret < 0) { LOG_ERR("Failed to trigger command %d on TX: %d", I2S_TRIGGER_START, ret); return ret; } ret = i2s_trigger(cfg->dev, I2S_DIR_TX, I2S_TRIGGER_DRAIN); if (ret < 0) { LOG_ERR("Failed to trigger command %d on TX: %d", I2S_TRIGGER_DRAIN, ret); return ret; } /* Wait until transaction is over */ flush_time_us = cfg->lrck_period * cfg->tx_buf_bytes / sizeof(uint32_t); k_usleep(flush_time_us + cfg->extra_wait_time_us); return ret; } static size_t ws2812_strip_length(const struct device *dev) { const struct ws2812_i2s_cfg *cfg = dev->config; return cfg->length; } static int ws2812_i2s_init(const struct device *dev) { const struct ws2812_i2s_cfg *cfg = dev->config; struct i2s_config config; uint32_t lrck_hz; int ret; lrck_hz = USEC_PER_SEC / cfg->lrck_period; LOG_DBG("Word clock: freq %u Hz period %u us", lrck_hz, cfg->lrck_period); /* 16-bit stereo, 100kHz LCLK */ config.word_size = 16; config.channels = 2; config.format = I2S_FMT_DATA_FORMAT_I2S; config.options = I2S_OPT_BIT_CLK_MASTER | I2S_OPT_FRAME_CLK_MASTER; config.frame_clk_freq = lrck_hz; /* WS (or LRCK) */ config.mem_slab = cfg->mem_slab; config.block_size = cfg->tx_buf_bytes; config.timeout = 1000; ret = i2s_configure(cfg->dev, I2S_DIR_TX, &config); if (ret < 0) { LOG_ERR("Failed to configure I2S device: %d\n", ret); return ret; } for (uint16_t i = 0; i < cfg->num_colors; i++) { switch (cfg->color_mapping[i]) { case LED_COLOR_ID_WHITE: case LED_COLOR_ID_RED: case LED_COLOR_ID_GREEN: case LED_COLOR_ID_BLUE: break; default: LOG_ERR("%s: invalid channel to color mapping." "Check the color-mapping DT property", dev->name); return -EINVAL; } } return 0; } static DEVICE_API(led_strip, ws2812_i2s_api) = { .update_rgb = ws2812_strip_update_rgb, .length = ws2812_strip_length, }; #define WS2812_I2S_LRCK_PERIOD_US(idx) DT_INST_PROP(idx, lrck_period) #define WS2812_RESET_DELAY_US(idx) DT_INST_PROP(idx, reset_delay) /* Rounds up to the next 20us. */ #define WS2812_RESET_DELAY_WORDS(idx) \ DIV_ROUND_UP(WS2812_RESET_DELAY_US(idx), WS2812_I2S_LRCK_PERIOD_US(idx)) #define WS2812_NUM_COLORS(idx) (DT_INST_PROP_LEN(idx, color_mapping)) #define WS2812_I2S_NUM_PIXELS(idx) (DT_INST_PROP(idx, chain_length)) #define WS2812_I2S_BUFSIZE(idx) \ (((WS2812_NUM_COLORS(idx) * WS2812_I2S_NUM_PIXELS(idx)) + \ WS2812_I2S_PRE_DELAY_WORDS + WS2812_RESET_DELAY_WORDS(idx)) * 4) #define WS2812_I2S_DEVICE(idx) \ \ K_MEM_SLAB_DEFINE_STATIC(ws2812_i2s_##idx##_slab, WS2812_I2S_BUFSIZE(idx), 2, 4); \ \ static const uint8_t ws2812_i2s_##idx##_color_mapping[] = \ DT_INST_PROP(idx, color_mapping); \ \ static const struct ws2812_i2s_cfg ws2812_i2s_##idx##_cfg = { \ .dev = DEVICE_DT_GET(DT_INST_BUS(idx)), \ .tx_buf_bytes = WS2812_I2S_BUFSIZE(idx), \ .mem_slab = &ws2812_i2s_##idx##_slab, \ .num_colors = WS2812_NUM_COLORS(idx), \ .length = DT_INST_PROP(idx, chain_length), \ .color_mapping = ws2812_i2s_##idx##_color_mapping, \ .lrck_period = WS2812_I2S_LRCK_PERIOD_US(idx), \ .extra_wait_time_us = DT_INST_PROP(idx, extra_wait_time), \ .reset_words = WS2812_RESET_DELAY_WORDS(idx), \ .active_low = DT_INST_PROP(idx, out_active_low), \ .nibble_one = DT_INST_PROP(idx, nibble_one), \ .nibble_zero = DT_INST_PROP(idx, nibble_zero), \ }; \ \ DEVICE_DT_INST_DEFINE(idx, ws2812_i2s_init, NULL, NULL, &ws2812_i2s_##idx##_cfg, \ POST_KERNEL, CONFIG_LED_STRIP_INIT_PRIORITY, &ws2812_i2s_api); DT_INST_FOREACH_STATUS_OKAY(WS2812_I2S_DEVICE)