add stepper

Author: iitzex

README.md

@@ -1,6 +1,8 @@
 # MicroPython-NodeMCU
 Command for burn flash
 ```python
+boot.py : auto loading code after boot
+
 deploy : quick command to modify the serial port and baud rate w/ fast speed
         port = /dev/tty.SLAB_USBtoUART
         baud = 921600
@@ -23,4 +25,6 @@ led_breath_timer.py : make LED light and dim
         software PWM, Timer
         set each period w/ timer
 
+stepper.py : use 28BYJ-48 5V DC stepper
+
 ```

stepper.py

@@ -0,0 +1,43 @@
+from pyb import Pin
+from time import sleep_ms, sleep_us
+
+D1 = Pin(5, Pin.OUT)
+D2 = Pin(4, Pin.OUT)
+D3 = Pin(0, Pin.OUT)
+D4 = Pin(2, Pin.OUT)
+
+#steps of revolution = 4096, 8*512
+seq = [[0,0,0,1],
+       [0,0,1,1],
+       [0,0,1,0],
+       [0,1,1,0],
+       [0,1,0,0],
+       [1,1,0,0],
+       [1,0,0,0],
+       [1,0,0,1]]
+
+def rotate(RPM, angle):
+    if(RPM > 20):
+        print("RPM should less than 20")
+        return
+    delay = int(60*1000*1000/4096/RPM)
+    steps = int(512*abs(angle)/360)
+    if angle < 0:
+        direction = -1
+    else:
+        direction = 1
+    for i in range(steps):
+        for step in seq[::direction]:
+            set_step(step)
+            sleep_us(delay)
+
+def set_step(step):
+    D1.value(int(step[0]))
+    D2.value(int(step[1]))
+    D3.value(int(step[2]))
+    D4.value(int(step[3]))
+
+for i in range(1):
+    rotate(20, 360)
+
+#