litex/misoclib/uart/__init__.py

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from migen.fhdl.std import *
from migen.genlib.cdc import MultiReg
from migen.bank.description import *
from migen.bank.eventmanager import *
from migen.genlib.record import Record
from migen.sim.generic import Simulator, TopLevel
from migen.sim import icarus
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class UART(Module, AutoCSR):
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def __init__(self, pads, clk_freq, baud=115200):
self._r_rxtx = CSR(8)
self.submodules.ev = EventManager()
self.ev.tx = EventSourceProcess()
self.ev.rx = EventSourcePulse()
self.ev.finalize()
# Tuning word value
tuning_word=int((baud/clk_freq)*2**32)
self._r_tuning_word = CSRStorage(32, reset=tuning_word)
###
uart_clk_rxen = Signal()
uart_clk_txen = Signal()
phase_accumulator_rx = Signal(32)
phase_accumulator_tx = Signal(32)
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pads.tx.reset = 1
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# TX
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tx_reg = Signal(8)
tx_bitcount = Signal(4)
tx_busy = self.ev.tx.trigger
self.sync += [
If(self._r_rxtx.re,
tx_reg.eq(self._r_rxtx.r),
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tx_bitcount.eq(0),
tx_busy.eq(1),
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pads.tx.eq(0)
).Elif(uart_clk_txen & tx_busy,
tx_bitcount.eq(tx_bitcount + 1),
If(tx_bitcount == 8,
pads.tx.eq(1)
).Elif(tx_bitcount == 9,
pads.tx.eq(1),
tx_busy.eq(0)
).Else(
pads.tx.eq(tx_reg[0]),
tx_reg.eq(Cat(tx_reg[1:], 0))
)
)
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]
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# RX
rx = Signal()
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self.specials += MultiReg(pads.rx, rx)
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rx_r = Signal()
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rx_reg = Signal(8)
rx_bitcount = Signal(4)
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rx_busy = Signal()
rx_done = self.ev.rx.trigger
rx_data = self._r_rxtx.w
self.sync += [
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rx_done.eq(0),
rx_r.eq(rx),
If(~rx_busy,
If(~rx & rx_r, # look for start bit
rx_busy.eq(1),
rx_bitcount.eq(0),
)
).Else(
If(uart_clk_rxen,
rx_bitcount.eq(rx_bitcount + 1),
If(rx_bitcount == 0,
If(rx, # verify start bit
rx_busy.eq(0)
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)
).Elif(rx_bitcount == 9,
rx_busy.eq(0),
If(rx, # verify stop bit
rx_data.eq(rx_reg),
rx_done.eq(1)
)
).Else(
rx_reg.eq(Cat(rx_reg[1:], rx))
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)
)
)
]
self.sync += [
If(rx_busy,
Cat(phase_accumulator_rx, uart_clk_rxen).eq(phase_accumulator_rx + self._r_tuning_word.storage)
).Else(
Cat(phase_accumulator_rx, uart_clk_rxen).eq(2**31)
),
If(tx_busy,
Cat(phase_accumulator_tx, uart_clk_txen).eq(phase_accumulator_tx + self._r_tuning_word.storage)
).Else(
Cat(phase_accumulator_tx, uart_clk_txen).eq(0)
)
]
class UARTTB(Module):
def __init__(self):
MHz=1000000
self.clk_freq = 83333333
self.baud = 3*MHz
self.pads = Record([("rx", 1), ("tx", 1)])
self.submodules.slave = UART(self.pads, self.clk_freq, self.baud)
def wait_for(self, ns_time):
freq_in_ghz = self.clk_freq/(10**9)
period = 1/freq_in_ghz
num_loops = int(ns_time/period)
for i in range(num_loops+1):
yield
def gen_simulation(self, selfp):
baud_in_ghz = self.baud/(10**9)
uart_period = int(1/baud_in_ghz)
half_uart_period = int(1/(2*baud_in_ghz))
# Set TX an RX lines idle
selfp.pads.tx = 1
selfp.pads.rx = 1
yield
# First send a few characters
tx_string = "01234"
print("Sending string: " + tx_string)
for c in tx_string:
while selfp.slave.ev.tx.trigger == 1:
yield
selfp.slave._r_rxtx.r = ord(c)
selfp.slave._r_rxtx.re = 1
yield
selfp.slave._r_rxtx.re = 0
yield from self.wait_for(half_uart_period)
if selfp.pads.tx:
print("FAILURE: no start bit sent")
val = 0
for i in range(8):
yield from self.wait_for(uart_period)
val >>= 1
if selfp.pads.tx:
val |= 0x80
yield from self.wait_for(uart_period)
if selfp.pads.tx == 0:
print("FAILURE: no stop bit sent")
if ord(c) != val:
print("FAILURE: sent decimal value "+str(val)+" (char "+chr(val)+") instead of "+c)
else:
print("SUCCESS: sent "+c)
# Then receive a character
rx_string = '5'
print("Receiving character "+rx_string)
rx_value = ord(rx_string)
for i in range(11):
if (i == 0):
# start bit
selfp.pads.rx = 0
elif (i == 9):
# stop bit
selfp.pads.rx = 1
elif (i == 10):
selfp.pads.rx = 1
break
else:
selfp.pads.rx = 1 if (rx_value & 1) else 0
rx_value >>= 1
yield from self.wait_for(uart_period)
rx_value = ord(rx_string)
received_value = selfp.slave._r_rxtx.w
if (received_value == rx_value):
print("RX SUCCESS: ")
else:
print("RX FAILURE: ")
print("received "+chr(received_value))
while True:
yield
if __name__ == "__main__":
with Simulator(UARTTB(), TopLevel("top.vcd", clk_period=int(1/0.08333333)), icarus.Runner(keep_files=False)) as s:
s.run(20000)