pdq2: config writes

artiq/coredevice/pdq2.py

@@ -0,0 +1,70 @@
+from artiq.language.core import (kernel, portable, delay_mu, delay)
+from artiq.language.units import ns, us
+from artiq.coredevice import spi
+
+
+_PDQ2_SPI_CONFIG = (
+        0*spi.SPI_OFFLINE | 0*spi.SPI_CS_POLARITY |
+        0*spi.SPI_CLK_POLARITY | 0*spi.SPI_CLK_PHASE |
+        0*spi.SPI_LSB_FIRST | 0*spi.SPI_HALF_DUPLEX
+        )
+
+
+@portable
+def _PDQ2_CMD(board, is_mem, adr, we):
+    return (adr << 0) | (is_mem << 2) | (board << 3) | (we << 7)
+
+
+_PDQ2_ADR_CONFIG = 0
+_PDQ2_ADR_CRC = 1
+_PDQ2_ADR_FRAME = 2
+
+
+class PDQ2:
+    """
+
+    :param spi_device: Name of the SPI bus this device is on.
+    :param chip_select: Value to drive on the chip select lines
+      during transactions.
+    """
+
+    def __init__(self, dmgr, spi_device, chip_select=1):
+        self.core = dmgr.get("core")
+        self.bus = dmgr.get(spi_device)
+        self.chip_select = chip_select
+
+    @kernel
+    def setup_bus(self, write_div=4, read_div=15):
+        """Configure the SPI bus and the SPI transaction parameters
+        for this device. This method has to be called before any other method
+        if the bus has been used to access a different device in the meantime.
+
+        This method advances the timeline by the duration of two
+        RTIO-to-Wishbone bus transactions.
+
+        :param write_div: Write clock divider.
+        :param read_div: Read clock divider.
+        """
+        # write: 4*8ns >= 20ns = 2*clk (clock de-glitching 50MHz)
+        # read: 15*8*ns >= ~100ns = 5*clk (clk de-glitching latency + miso
+        #   latency)
+        self.bus.set_config_mu(_PDQ2_SPI_CONFIG, write_div, read_div)
+        self.bus.set_xfer(self.chip_select, 16, 0)
+
+    @kernel
+    def write(self, data):
+        """Write 16 bits of data.
+
+        This method advances the timeline by the duration of the SPI transfer
+        and the required CS high time.
+        """
+        self.bus.write(data << 16)
+        delay_mu(self.bus.ref_period_mu)  # get to 20ns min cs high
+
+    @kernel
+    def write_config(self, config, board=0xf):
+        board &= 0xf
+        self.write(
+                (_PDQ2_CMD(board, 0, _PDQ2_ADR_CONFIG, 1) << 24) |
+                (config << 16)
+                )