Chapter 6 code

ch-6/2-techniques/extract_a_bit.py

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+"""Sometimes we want to extract a specific bit for
+comparison or testing"""
+"""Shifting a register."""
+import rp2pio
+import adafruit_pioasm
+import array
+
+# extracting bit 2
+bit_to_extract = 30
+program = f"""
+.program extract_bit
+    pull block
+
+; print initial state
+    mov isr, osr
+    push noblock    ; and use PUSH to put it on the receive FIFO
+
+; extract - by shifting
+    in osr, {bit_to_extract}  ; get n bits
+    in null, 31  ; keep only 1 bit
+    push noblock
+"""
+
+assembled = adafruit_pioasm.assemble(program)
+
+## set up a statemachine
+sm = rp2pio.StateMachine(
+    assembled,
+    frequency=2000,
+)
+
+
+buffer = array.array('I', [0])
+
+sm.write(array.array('I', [0b01101000_00000000_00000000_00000000]))
+# read the data
+sm.readinto(buffer)
+print("Initial Y: {0} 0b{0:032b} 0x{0:x}".format(buffer[0]))
+
+sm.readinto(buffer)
+print("Y bit extracted:  {0} 0b{0:032b} 0x{0:x}".format(buffer[0]))
+
+