from machine import Pin
from time import sleep_ms, sleep_us, ticks_us

CLK  = Pin(10, Pin.OUT)
DATA = Pin(11, Pin.OUT)
CS   = Pin(9, Pin.OUT)

def MCP4921(X):
    X = X & 0x0FFF
    X = X | 0x3000
    
    CS.value(0)
    CLK.value(0)
    sleep_us(1)
    for i in range(0,16):
        if(X & (0x8000 >> i)):
            DATA.value(1)
        else:
            DATA.value(0)
        CLK.value(1)
        sleep_us(1)
        CLK.value(0)
        sleep_us(1)
    CS.value(1)
    DATA.value(0)
    sleep_ms(1)
 
x = 0
while(1):
    x = (x + 10) & 0x0FFF
    t0 = ticks_us()
    MCP4921(x)
    t1 = ticks_us()
    print(t1 - t0)
    sleep_ms(1)