Add bb_spi_controller

Bit banged spi controller, very simple but very slow.

hw/fpga/bb_spi_controller.sv

@@ -0,0 +1,43 @@
+module bb_spi_controller(
+    input clk,
+    input rst,
+    
+    input spi_cs,
+
+    input logic [7:0] data_in,
+    output logic [7:0] data_out,
+    
+    input rw,
+    
+    output logic SPI_SSn,
+    output logic SPI_MOSI,
+    output logic SPI_SCLK,
+    input SPI_MISO,
+    input SPI_slave_IRQ
+);
+
+logic [7:0] val;
+
+
+
+assign data_out = val;
+
+        
+assign SPI_SCLK = val[0];
+assign SPI_SSn = val[1];
+assign SPI_MOSI = val[2];
+
+always @(posedge clk) begin
+    if (rst) begin
+        val <= 8'h2;  //start with SS high
+    end
+    
+    if (spi_cs & ~rw)
+        val <= data_in;
+        
+    val[3] <= SPI_MISO;
+    val[4] <= SPI_slave_IRQ;
+end
+
+
+endmodule