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neopixel: Rework timing so that it works on AVR micro-controllers 

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2019-08-07 15:34:08 -04:00
parent 383fb1dbfd
commit f6d1ab2ea2
2 changed files with 101 additions and 66 deletions
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3
klippy/extras/neopixel.py
View File

@ -35,9 +35,6 @@ class PrinterNeoPixel:
self.cmd_SET_LED,
desc=self.cmd_SET_LED_help)
def build_config(self):
if self.mcu.get_constant_float('CLOCK_FREQ') <= 20000000:
raise self.printer.config_error(
"Neopixel is not supported on AVR micro-controllers")
cmd_queue = self.mcu.alloc_command_queue()
self.neopixel_send_cmd = self.mcu.lookup_command(
"neopixel_send oid=%c data=%*s", cq=cmd_queue)

164
src/neopixel.c
View File

@ -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;
// 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);
// 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;
} 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))
// Long pulse
neopixel_delay(last_start, 1250);
irq_disable();
neopixel_time_t start = neopixel_get_time();
gpio_out_toggle_noirq(pin);
irq_enable();
if (neopixel_check_elapsed(last_start, start, 4000))
goto fail;
last_start = start;
byte <<= 1;
neopixel_delay(start, 650);
irq_disable();
gpio_out_toggle_noirq(pin);
irq_enable();
} else {
// 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