soc: add DDS interface core

soc/artiqlib/ad9858/__init__.py

@@ -0,0 +1,172 @@
+from migen.fhdl.std import *
+from migen.genlib.fsm import *
+from migen.bus import wishbone
+from migen.bus.transactions import *
+from migen.sim.generic import run_simulation
+
+class AD9858(Module):
+	"""Wishbone interface to the AD9858 DDS chip.
+
+	Addresses 0-63 map the AD9858 registers.
+	Data is zero-padded.
+
+	Write to address 64 to pulse the FUD signal.
+	Address 65 is a GPIO register that controls	the sel, p and reset signals.
+	sel is mapped to the lower bits, followed by p and reset.
+
+	Write timing:
+	Address is set one cycle before assertion of we_n.
+	we_n is asserted for one cycle, at the same time as valid data is driven.
+
+	Read timing:
+	Address is set one cycle before assertion of rd_n.
+	rd_n is asserted for 3 cycles.
+	Data is sampled 2 cycles into the assertion of rd_n.
+
+	FUD is asserted for fud_cycles cycles.
+	"""
+	def __init__(self, pads, fud_cycles=3, bus=None):
+		if bus is None:
+			bus = wishbone.Interface()
+		self.bus = bus
+
+		###
+
+		dts = TSTriple(8)
+		self.specials += dts.get_tristate(pads.d)
+		dr = Signal(8)
+		oe_p = Signal()
+		self.sync += [
+			pads.a.eq(bus.adr[:6]),
+			dts.o.eq(bus.dat_w),
+			dr.eq(dts.i),
+			dts.oe.eq(oe_p)
+		]
+
+		gpio = Signal(flen(pads.sel) + flen(pads.p) + 1)
+		gpio_load = Signal()
+		self.sync += If(gpio_load, gpio.eq(bus.dat_w))
+		self.comb += Cat(pads.sel, pads.p, pads.reset).eq(gpio)
+
+		bus_r_sel_gpio = Signal()
+		self.comb += If(bus_r_sel_gpio,
+				bus.dat_r.eq(gpio)
+			).Else(
+				bus.dat_r.eq(dr)
+			)
+
+		fud_p = Signal()
+		self.sync += pads.fud.eq(fud_p)
+		fud_counter_max = fud_cycles - 1
+		fud_counter = Signal(max=fud_counter_max+1)
+		fud_counter_en = Signal()
+		fud_counter_done = Signal()
+		self.comb += fud_counter_done.eq(fud_counter == fud_counter_max)
+		self.sync += If(fud_counter_en,
+				fud_counter.eq(fud_counter + 1)
+			).Else(
+				fud_counter.eq(0)
+			)
+
+		pads.wr_n.reset = 1
+		pads.rd_n.reset = 1
+		wr_n_p = Signal(reset=1)
+		rd_n_p = Signal(reset=1)
+		self.sync += pads.wr_n.eq(wr_n_p), pads.rd_n.eq(rd_n_p)
+
+		fsm = FSM()
+		self.submodules += fsm
+
+		fsm.act("IDLE",
+			If(bus.cyc & bus.stb,
+				If(bus.adr[6],
+					If(bus.adr[0],
+						NextState("GPIO")
+					).Else(
+						NextState("FUD")
+					)
+				).Else(
+					If(bus.we,
+						NextState("WRITE")
+					).Else(
+						NextState("READ")
+					)
+				)
+			)
+		)
+		fsm.act("WRITE",
+			oe_p.eq(1),
+			wr_n_p.eq(0),
+			bus.ack.eq(1),
+			NextState("IDLE")
+		)
+		fsm.act("READ",
+			rd_n_p.eq(0),
+			NextState("READ0")
+		)
+		fsm.act("READ0",
+			rd_n_p.eq(0),
+			NextState("READ1")
+		)
+		fsm.act("READ1",
+			rd_n_p.eq(0),
+			NextState("READ2")
+		)
+		fsm.act("READ2",
+			NextState("READ3")
+		)
+		fsm.act("READ3",
+			bus.ack.eq(1),
+			NextState("IDLE")
+		)
+		fsm.act("GPIO",
+			bus.ack.eq(1),
+			bus_r_sel_gpio.eq(1),
+			If(bus.we, gpio_load.eq(1)),
+			NextState("IDLE")
+		)
+		fsm.act("FUD",
+			fud_p.eq(1),
+			fud_counter_en.eq(1),
+			If(fud_counter_done,
+				bus.ack.eq(1),
+				NextState("IDLE")
+			)
+		)
+
+def _test_gen():
+	# Test external bus writes
+	yield TWrite(4, 2)
+	yield TWrite(5, 3)
+
+	# Test external bus reads
+	yield TRead(14)
+	yield TRead(15)
+
+	# Test FUD
+	yield TWrite(64, 0)
+
+	# Test GPIO
+	yield TWrite(65, 0xff)
+	yield None
+
+class _TestPads:
+	def __init__(self):
+		self.a = Signal(6)
+		self.d = Signal(8)
+		self.sel = Signal(5)
+		self.p = Signal(2)
+		self.fud = Signal()
+		self.wr_n = Signal()
+		self.rd_n = Signal()
+		self.reset = Signal()
+
+class _TB(Module):
+	def __init__(self):
+		pads = _TestPads()
+		self.submodules.dut = AD9858(pads)
+		self.submodules.initiator = wishbone.Initiator(_test_gen())
+		self.submodules.interconnect = wishbone.InterconnectPointToPoint(self.initiator.bus, self.dut.bus)
+
+if __name__ == "__main__":
+	run_simulation(_TB(), vcd_name="ad9858.vcd")

soc/targets/artiq.py

@@ -7,7 +7,7 @@ from misoclib import lasmicon, spiflash, gpio
 from misoclib.sdramphy import gensdrphy
 from misoclib.gensoc import SDRAMSoC
 
-from artiqlib import rtio
+from artiqlib import rtio, ad9858
 
 class _CRG(Module):
 	def __init__(self, platform, clk_freq):
@@ -124,5 +124,7 @@ class ARTIQSoC(SDRAMSoC):
 			platform.request("user_led", 1)))
 		self.comb += platform.request("ttl_tx_en").eq(1)
 		self.submodules.rtio = rtio.RTIO([platform.request("ttl", i) for i in range(4)])
+		self.submodules.dds = ad9858.AD9858(platform.request("dds"))
+		self.add_wb_slave(lambda a: a[26:29] == 3, self.dds.bus)
 
 default_subtarget = ARTIQSoC