from machine import Pin, SPI
from utime import sleep_ms

VREF = 2.5

spi = SPI(0, baudrate=1000000, polarity=0, phase=0, sck=Pin(2), mosi=Pin(3))
cs = Pin(5, Pin.OUT)
cs.value(1)

def set_dac_code(code):
    code &= 0x0FFF
    command = 0x3000 | code
    high_byte = (command >> 8) & 0xFF
    low_byte = command & 0xFF
    cs.value(0)
    spi.write(bytes([high_byte, low_byte]))
    cs.value(1)

def code_to_voltage(code):
    return VREF * code / 4096

clk = Pin(16, Pin.IN, Pin.PULL_UP)
dt = Pin(17, Pin.IN, Pin.PULL_UP)

_delta = 0
_last_clk = clk.value()

def _on_clk(pin):
    global _delta, _last_clk
    state = clk.value()
    if state != _last_clk:
        _delta += 1 if dt.value() != state else -1
    _last_clk = state

clk.irq(trigger=Pin.IRQ_FALLING | Pin.IRQ_RISING, handler=_on_clk)

CODE_STEP = 40  # raw code per detent (~0.024V at VREF=2.5)
setpoint_code = 0
set_dac_code(setpoint_code)

while True:
    delta, _delta = _delta, 0
    if delta != 0:
        setpoint_code = max(0, min(4095, setpoint_code + delta * CODE_STEP))
        set_dac_code(setpoint_code)
        print("Code:", setpoint_code, " Voltage:", round(code_to_voltage(setpoint_code), 4), "V")
    sleep_ms(20)