Merge pull request #6312 from dhalbert/adjust-neopixel-timings

test and adjust NeoPixel timings on multiple ports

Author: dhalbert

ports/atmel-samd/common-hal/neopixel_write/__init__.c

@@ -46,6 +46,9 @@ __attribute__((naked,noinline,aligned(16)))
 static void neopixel_send_buffer_core(volatile uint32_t *clraddr, uint32_t pinMask,
     const uint8_t *ptr, int numBytes);
 
+// The SAMD21 timing loop durations below are approximate,
+// because the other instructions take significant time.
+
 static void neopixel_send_buffer_core(volatile uint32_t *clraddr, uint32_t pinMask,
     const uint8_t *ptr, int numBytes) {
     asm volatile ("        push    {r4, r5, r6, lr};"
@@ -54,25 +57,28 @@ static void neopixel_send_buffer_core(volatile uint32_t *clraddr, uint32_t pinMa
         "        ldrb r5, [r2, #0];"          // r5 := *ptr
         "        add  r2, #1;"                // ptr++
         "        movs    r4, #128;"           // r4-mask, 0x80
+
         "loopBit:"
         "        str r1, [r0, #4];"                             // set
         #ifdef SAMD21
-        "        movs r6, #3; d2: sub r6, #1; bne d2;"          // delay 3
+        "        movs r6, #2; d2: sub r6, #1; bne d2;"          // 248 ns high (entire T0H or start T1H)
         #endif
         #ifdef SAM_D5X_E5X
-        "        movs r6, #16; d2: subs r6, #1; bne d2;"          // delay 3
+        "        movs r6, #11; d2: subs r6, #1; bne d2;"        // 300 ns high (entire T0H or start T1H)
         #endif
         "        tst r4, r5;"                                   // mask&r5
         "        bne skipclr;"
         "        str r1, [r0, #0];"          // clr
+
         "skipclr:"
         #ifdef SAMD21
-        "        movs r6, #6; d0: sub r6, #1; bne d0;"          // delay 6
+        "        movs r6, #7; d0: sub r6, #1; bne d0;"          // 772 ns low or high (start T0L or end T1H)
         #endif
         #ifdef SAM_D5X_E5X
-        "        movs r6, #16; d0: subs r6, #1; bne d0;"          // delay 6
+        "        movs r6, #15; d0: subs r6, #1; bne d0;"        // 388 ns low or high (start T0L or end T1H)
         #endif
         "        str r1, [r0, #0];"            // clr (possibly again, doesn't matter)
+
         #ifdef SAMD21
         "        asr     r4, r4, #1;"          // mask >>= 1
         #endif
@@ -82,15 +88,20 @@ static void neopixel_send_buffer_core(volatile uint32_t *clraddr, uint32_t pinMa
         "        beq     nextbyte;"
         "        uxtb    r4, r4;"
         #ifdef SAMD21
-        "        movs r6, #2; d1: sub r6, #1; bne d1;"          // delay 2
+        "        movs r6, #5; d1: sub r6, #1; bne d1;"          // 496 ns (end TOL or entire T1L)
         #endif
         #ifdef SAM_D5X_E5X
-        "        movs r6, #15; d1: subs r6, #1; bne d1;"          // delay 2
+        "        movs r6, #20; d1: subs r6, #1; bne d1;"        // 548 ns (end TOL or entire T1L)
         #endif
         "        b       loopBit;"
+
         "nextbyte:"
-        #ifdef SAM_D5X_E5X
-        "        movs r6, #12; d3: subs r6, #1; bne d3;"          // delay 2
+        #ifdef SAMD21
+        "        movs r6, #1; d3: sub r6, #1; bne d3;"          // 60 ns (end TOL or entire T1L)
+                                                                // other instructions add more delay
+        #endif
+         #ifdef SAM_D5X_E5X
+        "        movs r6, #18; d3: subs r6, #1; bne d3;"        // extra for 936 ns total (byte end T0L or entire T1L)
         #endif
         "        cmp r2, r3;"
         "        bcs neopixel_stop;"

ports/espressif/common-hal/neopixel_write/__init__.c

@@ -47,11 +47,11 @@
 #include "components/driver/include/driver/rmt.h"
 #include "peripherals/rmt.h"
 
-// 416 ns is 1/3 of the 1250ns period of a 800khz signal.
-#define WS2812_T0H_NS (416)
-#define WS2812_T0L_NS (416 * 2)
-#define WS2812_T1H_NS (416 * 2)
-#define WS2812_T1L_NS (416)
+// Use closer to WS2812-style timings instead of WS2812B, to accommodate more varieties.
+#define WS2812_T0H_NS (316)
+#define WS2812_T0L_NS (316 * 3)
+#define WS2812_T1H_NS (700)
+#define WS2812_T1L_NS (564)
 
 static uint32_t ws2812_t0h_ticks = 0;
 static uint32_t ws2812_t1h_ticks = 0;

ports/nrf/common-hal/neopixel_write/__init__.c

@@ -53,13 +53,16 @@
 // The PWM starts the duty cycle in LOW. To start with HIGH we
 // need to set the 15th bit on each register.
 
+// *** CircuitPython: Use WS2812 for all, works with https://adafru.it/5225 and everything else
+// ***
+
 // WS2812 (rev A) timing is 0.35 and 0.7us
-// #define MAGIC_T0H               5UL | (0x8000) // 0.3125us
-// #define MAGIC_T1H              12UL | (0x8000) // 0.75us
+#define MAGIC_T0H               5UL | (0x8000) // 0.3125us
+#define MAGIC_T1H              12UL | (0x8000) // 0.75us
 
 // WS2812B (rev B) timing is 0.4 and 0.8 us
-#define MAGIC_T0H               6UL | (0x8000) // 0.375us
-#define MAGIC_T1H              13UL | (0x8000) // 0.8125us
+// #define MAGIC_T0H               6UL | (0x8000) // 0.375us
+// #define MAGIC_T1H              13UL | (0x8000) // 0.8125us
 #define CTOPVAL                20UL            // 1.25us
 
 // ---------- END Constants for the EasyDMA implementation -------------

ports/raspberrypi/common-hal/neopixel_write/__init__.c

@@ -35,23 +35,23 @@
 
 uint64_t next_start_raw_ticks = 0;
 
-// NeoPixels are 800khz bit streams. Zeroes are 1/3 duty cycle (~416ns) and ones
-// are 2/3 duty cycle (~833ns). Each of the instructions below take 1/3 duty
+// NeoPixels are 800khz bit streams. We are choosing zeros as <312ns hi, 936 lo> and ones
+// and ones as <700 ns hi, 556 ns lo>.
 // cycle. The first two instructions always run while only one of the two final
 // instructions run per bit. We start with the low period because it can be
-// longer than 1/3 period while waiting for more data.
+// longer while waiting for more data.
 const uint16_t neopixel_program[] = {
 // bitloop:
-//   out x 1        side 0 [1]; Side-set still takes place before instruction stalls
-    0x6121,
-//   jmp !x do_zero side 1 [1]; Branch on the bit we shifted out after 1/3 duty delay. Positive pulse
-    0x1123,
+//   out x 1        side 0 [6]; Drive low. Side-set still takes place before instruction stalls.
+    0x6621,
+//   jmp !x do_zero side 1 [3]; Branch on the bit we shifted out previous delay. Drive high.
+    0x1323,
 // do_one:
-//   jmp  bitloop   side 1 [1]; Continue driving high, for a long pulse
-    0x1100,
+//   jmp  bitloop   side 1 [4]; Continue driving high, for a one (long pulse)
+    0x1400,
 // do_zero:
-//   nop            side 0 [1]; Or drive low, for a short pulse
-    0xa142
+//   nop            side 0 [4]; Or drive low, for a zero (short pulse)
+    0xa442
 };
 
 void common_hal_neopixel_write(const digitalio_digitalinout_obj_t *digitalinout, uint8_t *pixels, uint32_t num_bytes) {
@@ -63,7 +63,7 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t *digitalinout,
     uint32_t pins_we_use = 1 << digitalinout->pin->number;
     bool ok = rp2pio_statemachine_construct(&state_machine,
         neopixel_program, sizeof(neopixel_program) / sizeof(neopixel_program[0]),
-        800000 * 6, // 800 khz * 6 cycles per bit
+        12800000, // MHz, to get about appropriate sub-bit times in PIO program.
         NULL, 0, // init program
         NULL, 1, // out
         NULL, 1, // in

ports/stm/common-hal/neopixel_write/__init__.c

@@ -38,8 +38,8 @@ uint64_t next_start_raw_ticks = 0;
 
 // sysclock divisors
 #define MAGIC_800_INT  900000  // ~1.11 us  -> 1.2  field
-#define MAGIC_800_T0H  2800000  // ~0.36 us -> 0.44 field
-#define MAGIC_800_T1H  1350000  // ~0.74 us -> 0.84 field
+#define MAGIC_800_T0H  3500000  // 300ns actual; 880 low
+#define MAGIC_800_T1H  1350000  // 768ns actual; 412 low
 
 #pragma GCC push_options
 #pragma GCC optimize ("Os")

shared-bindings/neopixel_write/__init__.c

@@ -32,6 +32,42 @@
 #include "shared-bindings/util.h"
 #include "supervisor/shared/translate.h"
 
+// RGB LED timing information:
+
+// From the WS2811 datasheet: high speed mode
+// - T0H 0 code,high voltage time 0.25 us +-150ns
+// - T1H 1 code,high voltage time 0.6  us +-150ns
+// - T0L 0 code,low voltage time 1.0 us +-150ns
+// - T1L 1 code,low voltage time 0.65 us +-150ns
+// - RES low voltage time Above 50us
+
+// From the SK6812 datasheet:
+// - T0H 0 code, high level time 0.3us +-0.15us
+// - T1H 1 code, high level time 0.6us +-0.15us
+// - T0L 0 code, low level time 0.9us +-0.15us
+// - T1L 1 code, low level time 0.6us +-0.15us
+// - Trst Reset code，low level time 80us
+
+// From the WS2812 datasheet:
+// - T0H 0 code, high voltage time 0.35us +-150ns
+// - T1H 1 code, high voltage time 0.7us +-150ns
+// - T0L 0 code, low voltage time 0.8us +-150ns
+// - T1L 1 code, low voltage time 0.6us +-150ns
+// - RES low voltage time Above 50us
+
+// From the WS28212B datasheet:
+// - T0H 0 code, high voltage time 0.4us +-150ns
+// - T1H 1 code, high voltage time 0.8us +-150ns
+// - T0L 0 code, low voltage time 0.85us +-150ns
+// - T1L 1 code, low voltage time 0.45us +-150ns
+// - RES low voltage time Above 50us
+
+// The timings used in various ports do not always follow the guidelines above.
+// In general, a zero bit is about 300ns high, 900ns low.
+// A one bit is about 700ns high, 500ns low.
+// But the ports vary based on implementation considerations; the proof is in the testing.
+// https://adafru.it/5225 is more sensitive to timing and should be included in testing.
+
 STATIC void check_for_deinit(digitalio_digitalinout_obj_t *self) {
     if (common_hal_digitalio_digitalinout_deinited(self)) {
         raise_deinited_error();