Create volume control module, not functional

dacVolume.py

@@ -0,0 +1,38 @@
+from migen import *
+
+from litex.soc.interconnect.csr import *
+from litex.soc.integration.doc import ModuleDoc
+
+# Test RGB Module ----------------------------------------------------------------------------------
+
+class DacVolume(Module, AutoCSR, ModuleDoc):
+    """
+    DAC Volume Control Module
+
+    Set the Attenuation of the PCM1780 DAC
+    """
+    def __init__(self, platform, pads):
+        platform.add_source("rtl/dacVolume.sv")
+
+        self.pads = pads
+        self.volume = CSRStorage(size = 8, reset = 128, description = "PCM1780: Attenuation Control")
+
+        self.m_sel_n = Signal()
+        self.m_clock = Signal()
+        self.m_data  = Signal()
+
+        # # #
+
+        self.specials += Instance("dacVolume",
+            i_i_clk48   = ClockSignal(),
+            i_i_rst48_n = ~ResetSignal(),
+            i_i_valid   = self.volume.re,
+            i_i_volume  = self.volume.storage,
+            o_o_sel_n   = self.m_sel_n,
+            o_o_clock   = self.m_clock,
+            o_o_data    = self.m_data,
+        )
+
+        self.comb += self.pads.ms.eq(self.m_sel_n) # Mode Bus: Select (Active Low)
+        self.comb += self.pads.mc.eq(self.m_clock) # Mode Bus: Clock
+        self.comb += self.pads.md.eq(self.m_data) # Mode Bus: Data

make.py

@@ -26,6 +26,7 @@ from litex.soc.cores.led import LedChaser
 from litedram.modules import MT41K64M16, MT41K128M16, MT41K256M16, MT41K512M16
 from litedram.phy import ECP5DDRPHY
 
+from dacVolume import DacVolume
 from testLED import TestLed
 from testRGB import TestRgb
 from testSaw import TestSaw
@@ -237,10 +238,20 @@ class BaseSoC(SoCCore):
             pads     = platform.request("dac_pcm")
         )
 
+        self.dac_vol = DacVolume(
+            platform = platform,
+            pads     = platform.request("dac_ctrl")
+        )
+
         # LiteScope Analyzer -----------------------------------------------------------------------
         self.add_uartbone(name="debug_uart", baudrate=921600)
         from litescope import LiteScopeAnalyzer
         analyzer_signals = [
+            self.dac_vol.volume.re,
+            self.dac_vol.volume.storage,
+            self.dac_vol.m_sel_n,
+            self.dac_vol.m_clock,
+            self.dac_vol.m_data,
             self.audio.targ0.re,
             # self.audio.targ0.storage,
             self.audio.wave0.re,
@@ -260,8 +271,10 @@ class BaseSoC(SoCCore):
         self.submodules.analyzer = LiteScopeAnalyzer(
             analyzer_signals,
             depth        = analyzer_depth,
-            clock_domain = "dac",
+            # clock_domain = "dac",
-            samplerate   = 36.92e6, # Actual clock frequency of DAC clock domain
+            clock_domain = "sys",
+            # samplerate   = 36.92e6, # Actual clock frequency of DAC clock domain
+            samplerate   = sys_clk_freq,
             csr_csv      = "analyzer.csv",
         )
 

rtl/dacVolume.sv

@@ -0,0 +1,48 @@
+`default_nettype none
+
+module dacVolume
+( input  var       i_clk48   // Runs at 48MHz
+, input  var       i_rst48_n // Active low reset for sys_clk
+, input  var       i_valid   // Only update DAC volume when CSRStorage is written to
+, input  var [7:0] i_volume  // 8-bit volume control (0x00 = min, 0xFF = max)
+, output var       o_sel_n   // DAC Control bus select (active low)
+, output var       o_clock   // DAC Control bus clock
+, output var       o_data    // DAC Control bus data (serial)
+);
+
+logic [7:0] valid;
+always_ff @(posedge i_clk48) // Capture when CSTStorage is written to
+  if (!i_rst48_n)   valid <= 8'h00;
+  else if (i_valid) valid <= 8'hFF;
+  else              valid <= {valid[6:0], 1'b0};
+
+logic [7:0] volume;
+always_ff @(posedge i_clk48) // Update volume setting when CSRStorage is written to
+  if (!i_rst48_n)   volume <= 8'h00;
+  else if (i_valid) volume <= i_volume;
+
+logic [2:0] div_6m;
+always_ff @(posedge i_clk48) // Count 6MHz cycle
+  if (!i_rst48_n) div_6m <= 3'b000;
+  else            div_6m <= div_6m + 1;
+
+always_comb o_clock = div_6m[2]; // Drive DAC Control bus clock at 6MHz
+
+logic _sel_n;
+logic _data;
+// always_comb o_sel_n = _sel_n; // Design fails to boot unless _sel_n optimised out
+// always_comb o_data  = _data;  // Design fails to boot unless _data optimised out
+
+logic [34:0] sel_n;
+always_ff @(negedge o_clock) // Update SEL_n on falling edge of CLOCK (As in PCM1780 Datasheet)
+  if (!i_rst48_n)    {_sel_n, sel_n} <= 36'hFFFFFFFFF;
+  else if (valid[7]) {_sel_n, sel_n} <= 36'h0000C0003;
+  else               {_sel_n, sel_n} <= {sel_n, 1'b1};
+
+logic [34:0] data;
+always_ff @(negedge o_clock) // Update DATA on falling edge of CLOCK (As in PCM1780 Datasheet)
+  if (!i_rst48_n)    {_data, data} <= 36'h000000000;
+  else if (valid[7]) {_data, data} <= {8'd16, volume, 2'd0, 8'd17, volume, 2'd0};
+  else               {_data, data} <= {data, 1'b0};
+
+endmodule