LiteX demo module

adder.c

#include <stdlib.h>
#include <stdbool.h>

#include <irq.h>
#include <libbase/uart.h>
#include <libbase/console.h>
#include <generated/csr.h>

#include "adder.h"

static void adder_wait(void)
{
    // wait for operation completion
    while (adder_ready_read() == 0) {}
}

void adder_reset(void)
{
    // reset adder
    adder_reset_write(true);

    adder_wait();    
}

void adder_add(uint32_t val)
{
    // perform addition
    adder_data_write(val);

    adder_wait();    
}

uint32_t adder_get(void)
{
    // return current result
    return adder_result_read();
}

adder.py

from migen import *

from litex.gen import *
from litex.soc.interconnect.csr import *
from litex.soc.interconnect.csr_eventmanager import *

class Adder(LiteXModule):

    LEN = 32

    def __init__(self):

        # control registers
        self.data = CSRStorage(self.LEN, description = "Number to add register.")
        self.reset = CSRStorage(1, description = "Reset register.")

        # status registers
        self.ready = CSRStatus(1, description = "Result ready register.")
        self.result = CSRStatus(self.LEN, description = "Result value register.")

        # incremental adder state machine
        self.fsm = FSM(reset_state = "ZERO")
        self.fsm.act("ZERO",

            # zero reset
            NextValue(self.reset.storage, 0),
        
            # zero addition result    
            NextValue(self.result.status, 0),

            # adder is ready
            NextValue(self.ready.status, 1),
            
            # wait for the number
            NextState("WAIT")
        )
        self.fsm.act("WAIT",

            # wait for the next state
            If(self.data.storage != 0,

                # adder is busy
                NextValue(self.ready.status, 0),

                # got addition number
                NextState("ADD")

            ).Elif(self.reset.storage != 0,

                # adder is busy
                NextValue(self.ready.status, 0),

                # got reset signal
                NextState("ZERO")
            )
        )
        self.fsm.act("ADD",

            # peform the addition
            NextValue(self.result.status, self.result.status + self.data.storage),

            # adder is ready
            NextValue(self.ready.status, 1),

            # zero addition number
            NextValue(self.data.storage, 0),

            # wait for the next number
            NextState("WAIT")
        )