atmel-samd: Add low level neopixel_write module & function for WS281x/neopixel RGB LEDs.

Author: tdicola

atmel-samd/Makefile

@@ -140,11 +140,13 @@ SRC_C = \
 	modmachine_dac.c \
 	modmachine_pin.c \
 	modmachine_pwm.c \
+	modneopixel_write.c \
 	moduos.c \
 	modutime.c \
 	mphalport.c \
 	pin_named_pins.c \
 	rom_fs.c \
+	samdneopixel.c \
 	storage.c \
 	uart.c \
 	asf/common/services/sleepmgr/samd/sleepmgr.c \

atmel-samd/modneopixel_write.c

@@ -0,0 +1,34 @@
+#include <stdio.h>
+
+#include "py/obj.h"
+#include "py/mphal.h"
+#include "py/runtime.h"
+
+#include "modmachine_pin.h"
+#include "samdneopixel.h"
+
+extern const mp_obj_type_t pin_type;
+
+STATIC mp_obj_t neopixel_write_neopixel_write_(mp_obj_t pin_obj, mp_obj_t buf, mp_obj_t is800k) {
+    // Convert parameters into expected types.
+    const pin_obj_t *pin = pin_find(pin_obj);
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(buf, &bufinfo, MP_BUFFER_READ);
+    // Call platform's neopixel write function with provided buffer and options.
+    samd_neopixel_write(pin->pin, (uint8_t*)bufinfo.buf, bufinfo.len,
+        mp_obj_is_true(is800k));
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(neopixel_write_neopixel_write_obj, neopixel_write_neopixel_write_);
+
+STATIC const mp_rom_map_elem_t neopixel_write_module_globals_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_neopixel_write) },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_neopixel_write), (mp_obj_t)&neopixel_write_neopixel_write_obj },
+};
+
+STATIC MP_DEFINE_CONST_DICT(neopixel_write_module_globals, neopixel_write_module_globals_table);
+
+const mp_obj_module_t neopixel_write_module = {
+    .base = { &mp_type_module },
+    .globals = (mp_obj_dict_t*)&neopixel_write_module_globals,
+};

atmel-samd/mpconfigport.h

@@ -108,11 +108,13 @@ typedef long mp_off_t;
 extern const struct _mp_obj_module_t machine_module;
 extern const struct _mp_obj_module_t uos_module;
 extern const struct _mp_obj_module_t utime_module;
+extern const struct _mp_obj_module_t neopixel_write_module;
 
 #define MICROPY_PORT_BUILTIN_MODULES \
     { MP_OBJ_NEW_QSTR(MP_QSTR_umachine), (mp_obj_t)&machine_module }, \
     { MP_OBJ_NEW_QSTR(MP_QSTR_uos), (mp_obj_t)&uos_module }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_utime), (mp_obj_t)&utime_module } \
+    { MP_OBJ_NEW_QSTR(MP_QSTR_utime), (mp_obj_t)&utime_module }, \
+    { MP_OBJ_NEW_QSTR(MP_QSTR_neopixel_write),(mp_obj_t)&neopixel_write_module } \
 
 #define MICROPY_PORT_BUILTIN_MODULE_WEAK_LINKS \
     { MP_OBJ_NEW_QSTR(MP_QSTR_machine), (mp_obj_t)&machine_module }, \

atmel-samd/samdneopixel.c

@@ -0,0 +1,87 @@
+#include "asf/common2/services/delay/delay.h"
+#include "asf/sam0/drivers/port/port.h"
+
+#include "samdneopixel.h"
+
+void samd_neopixel_write(uint32_t pin, uint8_t *pixels, uint32_t numBytes, bool is800KHz) {
+  // This is adapted directly from the Adafruit NeoPixel library SAMD21G18A code:
+  // https://github.com/adafruit/Adafruit_NeoPixel/blob/master/Adafruit_NeoPixel.cpp
+  uint8_t  *ptr, *end, p, bitMask;
+  uint32_t  pinMask;
+  PortGroup* port;
+
+  // Turn off interrupts of any kind during timing-sensitive code.
+  irqflags_t flags = cpu_irq_save();
+
+  port    =  port_get_group_from_gpio_pin(pin);
+  pinMask =  (1UL << (pin % 32));  // From port_pin_set_output_level ASF code.
+  ptr     =  pixels;
+  end     =  ptr + numBytes;
+  p       = *ptr++;
+  bitMask =  0x80;
+
+  volatile uint32_t *set = &(port->OUTSET.reg),
+                    *clr = &(port->OUTCLR.reg);
+
+  if(is800KHz) {
+    for(;;) {
+      *set = pinMask;
+      asm("nop; nop; nop; nop; nop; nop; nop; nop;");
+      if(p & bitMask) {
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop;");
+        *clr = pinMask;
+      } else {
+        *clr = pinMask;
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop;");
+      }
+      if(bitMask >>= 1) {
+        asm("nop; nop; nop; nop; nop; nop; nop; nop; nop;");
+      } else {
+        if(ptr >= end) break;
+        p       = *ptr++;
+        bitMask = 0x80;
+      }
+    }
+  } else { // 400 KHz bitstream
+    for(;;) {
+      *set = pinMask;
+      asm("nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;");
+      if(p & bitMask) {
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop;");
+        *clr = pinMask;
+      } else {
+        *clr = pinMask;
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop;");
+      }
+      asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+          "nop; nop; nop; nop; nop; nop; nop; nop;"
+          "nop; nop; nop; nop; nop; nop; nop; nop;"
+          "nop; nop; nop; nop; nop; nop; nop; nop;");
+      if(bitMask >>= 1) {
+        asm("nop; nop; nop; nop; nop; nop; nop;");
+      } else {
+        if(ptr >= end) break;
+        p       = *ptr++;
+        bitMask = 0x80;
+      }
+    }
+  }
+
+  // Turn on interrupts after timing-sensitive code.
+  cpu_irq_restore(flags);
+
+  // 50ms delay to let pixels latch to the data that was just sent.
+  // This could be optimized to only occur before pixel writes when necessary,
+  // like in the Arduino library.
+  delay_ms(50);
+}

atmel-samd/samdneopixel.h

@@ -0,0 +1,9 @@
+#ifndef SAMD_NEOPIXEL_WRITE_H
+#define SAMD_NEOPIXEL_WRITE_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+void samd_neopixel_write(uint32_t pin, uint8_t *pixels, uint32_t numBytes, bool is800KHz);
+
+#endif