importrp2frommachineimportPinimporttime@rp2.asm_pio(out_shiftdir=0,autopull=True,pull_thresh=8,autopush=True,push_thresh=8,sideset_init=(rp2.PIO.OUT_LOW,rp2.PIO.OUT_HIGH),out_init=rp2.PIO.OUT_LOW)defspi_cpha0():# Note X must be preinitialised by setup code before first byte, we reload after sending each byte# Would normally do this via exec() but in this case it's in the instruction memory and is only run onceset(x,6)# Actual program body followswrap_target()pull(ifempty)            .side(0x2)   [1]label("bitloop")out(pins,1)             .side(0x0)   [1]in_(pins,1)             .side(0x1)jmp(x_dec,"bitloop")    .side(0x1)out(pins,1)             .side(0x0)set(x,6)                .side(0x0)# Note this could be replaced with mov x, y for programmable frame sizein_(pins,1)             .side(0x1)jmp(not_osre,"bitloop") .side(0x1)# Fallthru if TXF emptiesnop()                    .side(0x0)   [1]# CSn back porchwrap()classPIOSPI:def__init__(self,sm_id,pin_mosi,pin_miso,pin_sck,cpha=False,cpol=False,freq=1000000):assert(not(cpolorcpha))self._sm=rp2.StateMachine(sm_id,spi_cpha0,freq=4*freq,sideset_base=Pin(pin_sck),out_base=Pin(pin_mosi),in_base=Pin(pin_sck))self._sm.active(1)self._sm.exec("set(x,6)")# Note this code will die spectacularly cause we're not draining the RX FIFOdefwrite_blocking(self,wdata):forbinwdata:self._sm.put(b<<24)defread_blocking(self,n):data= []foriinrange(n):data.append(self._sm.get()&0xff)returndatadefwrite_read_blocking(self,wdata):rdata= []forbinwdata:self._sm.put(b<<24)rdata.append(self._sm.get()&0xff)returnrdataspi=PIOSPI(0,19,16,18)cs_pin=machine.Pin(2,machine.Pin.OUT)defset_voltage(voltage):globalspiglobalcs_pin# Calculate the 10-bit digital value for the given voltagedigital_value=int(voltage/2.048*1023)# Calculate the configuration bits for output voltage range and power-down modeconfig_bits=0b00110000# 0b001 for full-scale output voltage range, 0b0 for normal mode# Send the configuration bits and digital value to the MCP4812 via SPIcs_pin.value(0)# Activate chip selectspi.write_blocking(bytes([(config_bits| ((digital_value>>6)&0xFF))]))spi.write_blocking(bytes([((digital_value&0x3F)<<2)]))cs_pin.value(1)# Deactivate chip selectspi.read_blocking(2)whileTrue:set_voltage(1.23)print("1.23")time.sleep(1)