diff options
Diffstat (limited to 'src/neopixel.c')
| -rw-r--r-- | src/neopixel.c | 160 |
1 files changed, 99 insertions, 61 deletions
diff --git a/src/neopixel.c b/src/neopixel.c index b799b516..57c865f2 100644 --- a/src/neopixel.c +++ b/src/neopixel.c @@ -11,6 +11,74 @@ #include "basecmd.h" // oid_alloc #include "command.h" // DECL_COMMAND +// The WS2812 uses a bit-banging protocol where each bit is +// transmitted as a gpio high pulse of variable length. The various +// specs are unclear, but it is believed the timing requirements are: +// - A zero bit must have a high pulse less than 500ns. +// - A one bit must have a high pulse longer than 650ns. +// - The total bit time (gpio high to following gpio high) must not +// exceed ~5000ns. The average bit time must be at least 1250ns. +// - The specs generally indicate a minimum high pulse and low pulse +// of 200ns, but the actual requirement might be smaller. + + + +/**************************************************************** + * Timing + ****************************************************************/ + +typedef unsigned int neopixel_time_t; + +static neopixel_time_t +nsecs_to_ticks(uint32_t ns) +{ + return timer_from_us(ns * 1000) / 1000000; +} + +static inline int +neopixel_check_elapsed(neopixel_time_t t1, neopixel_time_t t2, uint32_t nsecs) +{ + return t2 - t1 >= nsecs_to_ticks(nsecs); +} + +// The AVR micro-controllers require specialized timing +#if CONFIG_MACH_AVR + +#include <avr/interrupt.h> // TCNT1 + +static neopixel_time_t +neopixel_get_time(void) +{ + return TCNT1; +} + +static inline void +neopixel_delay(neopixel_time_t start, uint32_t nsecs) +{ +} + +#else + +static neopixel_time_t +neopixel_get_time(void) +{ + return timer_read_time(); +} + +static inline void +neopixel_delay(neopixel_time_t start, uint32_t nsecs) +{ + while (!neopixel_check_elapsed(start, neopixel_get_time(), nsecs)) + ; +} + +#endif + + +/**************************************************************** + * Neopixel interface + ****************************************************************/ + struct neopixel_s { struct gpio_out pin; uint32_t last_req_time; @@ -24,25 +92,7 @@ command_config_neopixel(uint32_t *args) , sizeof(*n)); n->pin = pin; } -#if !CONFIG_MACH_AVR DECL_COMMAND(command_config_neopixel, "config_neopixel oid=%c pin=%u"); -#endif - -static uint32_t -timer_from_ns(uint32_t ns) -{ - return timer_from_us(ns * 1000) / 1000000; -} - -// The WS2812 uses a bit-banging protocol where each bit is -// transmitted as a gpio high pulse of variable length. The various -// specs are unclear, but it is believed the timing requirements are: -// - A zero bit must have a high pulse less than 500ns. -// - A one bit must have a high pulse longer than 650ns. -// - The total bit time (gpio high to following gpio high) must not -// exceed ~5000ns. The average bit time must be at least 1250ns. -// - The specs generally indicate a minimum high pulse and low pulse -// of 200ns, but the actual requirement might be smaller. static int send_data(struct neopixel_s *n, uint8_t *data, uint_fast8_t data_len) @@ -55,61 +105,51 @@ send_data(struct neopixel_s *n, uint8_t *data, uint_fast8_t data_len) } struct gpio_out pin = n->pin; - uint32_t min_wait_time = cur, max_wait_time = cur + 0x40000000; + neopixel_time_t last_start = neopixel_get_time(); while (data_len--) { uint_fast8_t byte = *data++; uint_fast8_t bits = 8; while (bits--) { - // Calculate pulse duration - uint32_t on; - if (byte & 0x80) - on = timer_from_ns(650); - else - on = timer_from_ns(200); - - // Set output high - do { - irq_poll(); - cur = timer_read_time(); - } while (timer_is_before(cur, min_wait_time)); - uint32_t off_end_time = cur; - gpio_out_write(pin, 1); - uint32_t on_start_time = timer_read_time(); - min_wait_time = on_start_time + on; + if (byte & 0x80) { + // Long pulse + neopixel_delay(last_start, 1250); + irq_disable(); + neopixel_time_t start = neopixel_get_time(); + gpio_out_toggle_noirq(pin); + irq_enable(); - // Set output low - do { - irq_poll(); - cur = timer_read_time(); - } while (timer_is_before(cur, min_wait_time)); - uint32_t on_end_time = cur; - gpio_out_write(pin, 0); - uint32_t off_start_time = cur = timer_read_time(); - min_wait_time = on_start_time + timer_from_ns(1250); + if (neopixel_check_elapsed(last_start, start, 4000)) + goto fail; + last_start = start; + byte <<= 1; - // Check for faults - if (byte & 0x80) { - // Make sure off for at least 200ns - uint32_t min_off = off_start_time + timer_from_ns(200); - if (timer_is_before(min_wait_time, min_off)) - min_wait_time = min_off; + neopixel_delay(start, 650); + irq_disable(); + gpio_out_toggle_noirq(pin); + irq_enable(); } else { - // Make sure short on duration was no more than 500ns - uint32_t max_off = off_end_time + timer_from_ns(500); - if (timer_is_before(max_off, off_start_time)) + // Short pulse + neopixel_delay(last_start, 1250); + irq_disable(); + neopixel_time_t start = neopixel_get_time(); + gpio_out_toggle_noirq(pin); + neopixel_delay(start, 200); + gpio_out_toggle_noirq(pin); + irq_enable(); + + if (neopixel_check_elapsed(last_start, start, 4000)) goto fail; + last_start = start; + byte <<= 1; } - byte <<= 1; - if (timer_is_before(max_wait_time, on_start_time)) - goto fail; - max_wait_time = on_end_time + timer_from_us(4); } } - n->last_req_time = cur; + n->last_req_time = timer_read_time(); return 0; fail: // A hardware irq messed up the transmission - report a failure - n->last_req_time = cur; + gpio_out_write(pin, 0); + n->last_req_time = timer_read_time(); return -1; } @@ -128,6 +168,4 @@ command_neopixel_send(uint32_t *args) break; } } -#if !CONFIG_MACH_AVR DECL_COMMAND(command_neopixel_send, "neopixel_send oid=%c data=%*s"); -#endif |