litex/miscope/uart2wishbone.py

from migen.fhdl.std import *
from migen.genlib.record import *
from migen.genlib.fsm import FSM, NextState
from migen.genlib.misc import chooser
from migen.bank.description import *
from migen.bus import wishbone

from misoclib.uart import UARTRX, UARTTX

class UART(Module, AutoCSR):
	def __init__(self, pads, clk_freq, baud=115200):
		self._tuning_word = CSRStorage(32, reset=int((baud/clk_freq)*2**32))
		tuning_word = self._tuning_word.storage

		###

		self.submodules.rx = UARTRX(pads, tuning_word)
		self.submodules.tx = UARTTX(pads, tuning_word)

class Counter(Module):
	def __init__(self, width):
		self.value = Signal(width)
		self.clr = Signal()
		self.inc = Signal()
		self.sync += [
			If(self.clr,
				self.value.eq(0)
			).Elif(self.inc,
				self.value.eq(self.value+1)
			)
		]

class UARTPads:
	def __init__(self):
		self.rx = Signal()
		self.tx = Signal()

class UARTMux(Module):
	def __init__(self, pads):
		self.sel = Signal(max=2)
		self.shared_pads = UARTPads()
		self.bridge_pads = UARTPads()

	###
		# Route rx pad:
		# when sel==0, route it to shared rx and bridge rx
		# when sel==1, route it only to bridge rx
		self.comb += \
			If(self.sel==0,
				self.shared_pads.rx.eq(pads.rx),
				self.bridge_pads.rx.eq(pads.rx)
			).Else(
				self.bridge_pads.rx.eq(pads.rx)
			)

		# Route tx:
		# when sel==0, route shared tx to pads tx
		# when sel==1, route bridge tx to pads tx
		self.comb += \
			If(self.sel==0,
				pads.tx.eq(self.shared_pads.tx)
			).Else(
				pads.tx.eq(self.bridge_pads.tx)
			)

class UART2Wishbone(Module, AutoCSR):
	WRITE_CMD = 0x01
	READ_CMD = 0x02
	def __init__(self, pads, clk_freq, baud=115200, share_uart=False):

		# Wishbone interface
		self.wishbone = wishbone.Interface()
		if share_uart:
			self._sel = CSRStorage()

	###
		if share_uart:
			self.submodules.uart_mux = UARTMux(pads)
			self.submodules.uart = UART(self.uart_mux.bridge_pads, clk_freq, baud)
			self.shared_pads = self.uart_mux.shared_pads
			self.comb += self.uart_mux.sel.eq(self._sel.storage)
		else:
			self.submodules.uart = UART(pads, clk_freq, baud)

		uart = self.uart

		fsm = FSM()
		self.submodules += fsm

		word_cnt = Counter(3)
		burst_cnt = Counter(8)
		self.submodules += word_cnt, burst_cnt

		###
		cmd = Signal(8)
		fsm.act("WAIT_CMD",
			If(uart.rx.source.stb,
				If(	(uart.rx.source.payload.d == self.WRITE_CMD) |
					(uart.rx.source.payload.d == self.READ_CMD),
					NextState("RECEIVE_BURST_LENGTH")
				),
			word_cnt.clr.eq(1),
			burst_cnt.clr.eq(1)
			)
		)
		self.sync += If(fsm.ongoing("WAIT_CMD") & uart.rx.source.stb, cmd.eq(uart.rx.source.d))

		####
		burst_length = Signal(8)
		fsm.act("RECEIVE_BURST_LENGTH",
			word_cnt.inc.eq(uart.rx.source.stb),
			If(word_cnt.value == 1,
				word_cnt.clr.eq(1),
				NextState("RECEIVE_ADDRESS")
			)
		)
		self.sync += \
			If(fsm.ongoing("RECEIVE_BURST_LENGTH") & uart.rx.source.stb, burst_length.eq(uart.rx.source.d))

		####
		address = Signal(32)
		fsm.act("RECEIVE_ADDRESS",
			word_cnt.inc.eq(uart.rx.source.stb),
			If(word_cnt.value == 4,
				word_cnt.clr.eq(1),
				If(cmd == self.WRITE_CMD,
					NextState("RECEIVE_DATA")
				).Elif(cmd == self.READ_CMD,
					NextState("READ_DATA")
				)
			)
		)
		self.sync += \
			If(fsm.ongoing("RECEIVE_ADDRESS") & uart.rx.source.stb,
					address.eq(Cat(uart.rx.source.d, address[0:24]))
			)

		###
		data = Signal(32)

		###
		fsm.act("RECEIVE_DATA",
			word_cnt.inc.eq(uart.rx.source.stb),
			If(word_cnt.value == 4,
				word_cnt.clr.eq(1),
				NextState("WRITE_DATA")
			)
		)

		fsm.act("WRITE_DATA",
			self.wishbone.adr.eq(address + burst_cnt.value),
			self.wishbone.dat_w.eq(data),
			self.wishbone.sel.eq(2**flen(self.wishbone.sel)-1),
			self.wishbone.stb.eq(1),
			self.wishbone.we.eq(1),
			self.wishbone.cyc.eq(1),
			If(self.wishbone.ack,
				burst_cnt.inc.eq(1),
				If(burst_cnt.value == (burst_length-1),
					NextState("WAIT_CMD")
				).Else(
					word_cnt.clr.eq(1),
					NextState("RECEIVE_DATA")
				)
			)
		)

		###
		fsm.act("READ_DATA",
			self.wishbone.adr.eq(address + burst_cnt.value),
			self.wishbone.sel.eq(2**flen(self.wishbone.sel)-1),
			self.wishbone.stb.eq(1),
			self.wishbone.we.eq(0),
			self.wishbone.cyc.eq(1),
			If(self.wishbone.stb & self.wishbone.ack,
				word_cnt.clr.eq(1),
				NextState("SEND_DATA")
			)
		)

		fsm.act("SEND_DATA",
			word_cnt.inc.eq(uart.tx.sink.ack),
			If(word_cnt.value == 4,
				burst_cnt.inc.eq(1),
				If(burst_cnt.value == (burst_length-1),
					NextState("WAIT_CMD")
				).Else(
					NextState("READ_DATA")
				)
			),
			uart.tx.sink.stb.eq(1),
			chooser(data, word_cnt.value, uart.tx.sink.d, n=4, reverse=True)
		)

		###
		self.sync += \
			If(fsm.ongoing("RECEIVE_DATA") & uart.rx.source.stb,
				data.eq(Cat(uart.rx.source.d, data[0:24]))
			).Elif(fsm.ongoing("READ_DATA") & self.wishbone.stb & self.wishbone.ack,
				data.eq(self.wishbone.dat_r)
			)