Chapter 6 code

ch-6/2-techniques/shift_bits.py

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+"""Shifting a register.
+Default shift direction is in from the left.
+Space is made for the new value, and n bits from the source are 
+shifted in.
+"""
+import rp2pio
+import adafruit_pioasm
+import array
+
+
+program = f"""
+.program debug_register    
+    set y, {0b10011}       ; set a value in y
+
+; send it to be printed
+    mov isr, y
+    push noblock    ; and use PUSH to put it on the receive FIFO
+
+; shift pts
+    in null, 32     ; clear the isr
+    in y,3         ; get n bits from y
+
+    ; now send it to be printed
+    push noblock    ; and use PUSH to put it on the receive FIFO
+
+; show state of y
+    mov isr, y
+    push noblock
+"""
+
+assembled = adafruit_pioasm.assemble(program)
+
+## set up a statemachine
+sm = rp2pio.StateMachine(
+    assembled,
+    frequency=2000,
+)
+
+buffer = array.array('I', [0])
+
+# read the data
+sm.readinto(buffer)
+print("Before shift: {0} 0b{0:032b} 0x{0:x}".format(buffer[0]))
+
+sm.readinto(buffer)
+print("ISR shifted:  {0} 0b{0:032b} 0x{0:x}".format(buffer[0]))
+
+sm.readinto(buffer)
+print("Y state:      {0} 0b{0:032b} 0x{0:x}".format(buffer[0]))