spi: add coredevice support

artiq/coredevice/spi.py

@@ -0,0 +1,88 @@
+from artiq.language.core import *
+from artiq.language.types import *
+
+
+@syscall
+def spi_write(time_mu: TInt64, channel: TInt32, addr: TInt32, data: TInt32
+              ) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+
+@syscall
+def spi_read(time_mu: TInt64, channel: TInt32, addr: TInt32) -> TInt32:
+    raise NotImplementedError("syscall not simulated")
+
+
+SPI_DATA_ADDR, SPI_XFER_ADDR, SPI_CONFIG_ADDR = range(3)
+(
+    SPI_OFFLINE,
+    SPI_ACTIVE,
+    SPI_PENDING,
+    SPI_CS_POLARITY,
+    SPI_CLK_POLARITY,
+    SPI_CLK_PHASE,
+    SPI_LSB_FIRST,
+    SPI_HALF_DUPLEX,
+) = (1 << i for i in range(8))
+
+
+class SPIMaster:
+    """Core device Serial Peripheral Interface (SPI) bus master.
+
+    :param ref_period: clock period of the SPI core.
+    :param channel: channel number of the SPI bus to control.
+    """
+    def __init__(self, dmgr, ref_period, channel):
+        self.core = dmgr.get("core")
+        self.ref_period_mu = int(seconds_to_mu(ref_period, self.core), 64)
+        self.channel = channel
+        self.write_div = 0
+        self.read_div = 0
+        # a full transfer takes prep_mu + xfer_mu
+        self.prep_mu = int(0, 64)
+        # chaned transfers can happen every xfer_mu
+        self.xfer_mu = int(0, 64)
+        # The second transfer of a chain be written ref_period_mu
+        # after the first. Read data is available every xfer_mu starting
+        # a bit before prep_mu + xfer_mu.
+
+    @portable
+    def predict_xfer_mu(self, write_length, read_length):
+        # this is only the intrinsic bit cycle duration
+        return self.ref_period_mu*(
+            write_length*self.write_div +
+            read_length*self.read_div)
+
+    @portable
+    def predict_prep_mu(self, write_div):
+        return self.ref_period_mu*(
+            2 +  # intermediate transfers
+            # one write_div for the wait+idle cycle
+            self.write_div)
+
+    @kernel
+    def set_config(self, flags=0, write_div=6, read_div=6):
+        self.write_div = write_div
+        self.read_div = read_div
+        self.prep_mu = self.predict_prep_mu(write_div)
+        spi_write(now_mu(), self.channel, SPI_CONFIG_ADDR, flags |
+                  ((write_div - 2) << 8) | ((read_div - 2) << 20))
+        delay_mu(self.ref_period_mu)
+
+    @kernel
+    def set_xfer(self, chip_select=0, write_length=0, read_length=0):
+        self.xfer_mu = self.predict_xfer_mu(write_length, read_length)
+        spi_write(now_mu(), self.channel, SPI_XFER_ADDR,
+                  chip_select | (write_length << 16) | (read_length << 24))
+        delay_mu(self.ref_period_mu)
+
+    @kernel
+    def write(self, data):
+        spi_write(now_mu(), self.channel, SPI_DATA_ADDR, data)
+        delay_mu(self.prep_mu + self.xfer_mu)
+
+    @kernel
+    def read(self):
+        r = spi_read(now_mu(), self.channel, SPI_DATA_ADDR)
+        delay_mu(self.ref_period_mu)
+        return r