From 1bc6bb6857357e3cd2b3756bd9608db86e1fa456 Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Sun, 17 Apr 2022 15:57:29 -0700
Subject: Working (but very slow) RS232 UART

---
 hdl/top.sv | 133 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 132 insertions(+), 1 deletion(-)

(limited to 'hdl/top.sv')

diff --git a/hdl/top.sv b/hdl/top.sv
index 20294ff..ca45aa9 100644
--- a/hdl/top.sv
+++ b/hdl/top.sv
@@ -9,6 +9,9 @@ module top
     ,   inout   wire    [40:31] gpioc
     ,   output  wire            clock_out
 
+    ,   output  wire            rs232_tx
+    ,   input   wire            rs232_rx
+
     ,   output  bit             ram_resetn
     ,   output  bit             ram_csn
     ,   output  bit             ram_clkp
@@ -29,7 +32,91 @@ module top
         ,   .reset(internal_reset)
         );
 
-    assign clock_out = internal_clock;
+    //assign clock_out = internal_clock;
+
+    bit rs232_clock = 0;
+    bit [17:0] rs232_div = 0;
+    always @(posedge internal_clock) begin
+        if (internal_reset) begin
+            rs232_clock = 0;
+            rs232_div = 0;
+        end else begin
+            if (++rs232_div == 49987) begin // (30MHz/2)/300
+                ++rs232_clock;
+                rs232_div = 0;
+            end
+        end
+    end
+
+    assign clock_out = rs232_clock;
+
+    bit         wire_tx_ready;
+    bit         wire_tx_valid;
+    uart_byte_t wire_tx_data;
+
+    rs232_tx wiretx
+        (   .clock(rs232_clock)
+        ,   .reset(internal_reset)
+
+        ,   .out_ready(wire_tx_ready)
+        ,   .out_valid(wire_tx_valid)
+        ,   .out_data(wire_tx_data)
+
+        ,   .tx(rs232_tx)
+        );
+
+    bit         rs232_tx_ready;
+    bit         rs232_tx_valid;
+    uart_byte_t rs232_tx_data;
+
+    fifo
+        #(  .WIDTH_BITS($bits(uart_byte_t))
+        ) fifotx
+        (   .clock_in(internal_clock)
+        ,   .clock_out(rs232_clock)
+
+        ,   .in_ready(rs232_tx_ready)
+        ,   .in_valid(rs232_tx_valid)
+        ,   .in_data(rs232_tx_data)
+
+        ,   .out_ready(wire_tx_ready)
+        ,   .out_valid(wire_tx_valid)
+        ,   .out_data(wire_tx_data)
+        );
+
+    bit         wire_rx_ready;
+    bit         wire_rx_valid;
+    uart_byte_t wire_rx_data;
+
+    rs232_rx wirerx
+        (   .clock(rs232_clock)
+        ,   .reset(internal_reset)
+
+        ,   .in_ready(wire_rx_ready)
+        ,   .in_valid(wire_rx_valid)
+        ,   .in_data(wire_rx_data)
+
+        ,   .rx(rs232_rx)
+        );
+
+    bit         rs232_rx_ready;
+    bit         rs232_rx_valid;
+    uart_byte_t rs232_rx_data;
+
+    fifo
+        #(  .WIDTH_BITS($bits(uart_byte_t))
+        ) fiforx
+        (   .clock_in(rs232_clock)
+        ,   .clock_out(internal_clock)
+
+        ,   .in_ready(wire_rx_ready)
+        ,   .in_valid(wire_rx_valid)
+        ,   .in_data(wire_rx_data)
+
+        ,   .out_ready(rs232_rx_ready)
+        ,   .out_valid(rs232_rx_valid)
+        ,   .out_data(rs232_rx_data)
+        );
 
     bit         ram_rx_ready;
     bit         ram_rx_valid;
@@ -334,12 +421,28 @@ module top
         genvar i;
         for (i = 0; i < `NUM_PDPS; ++i) begin : core
 
+            bit         tx_ready;
+            bit         tx_valid;
+            uart_byte_t tx_data;
+
+            bit         rx_ready;
+            bit         rx_valid;
+            uart_byte_t rx_data;
+
             core
                 #(  .JTAG_INSTANCE(1+i)
                 ) cpu
                 (   .clk(internal_clock)
                 ,   .reset(internal_reset)
 
+                ,   .uart_tx_ready(tx_ready)
+                ,   .uart_tx_valid(tx_valid)
+                ,   .uart_tx_data(tx_data)
+
+                ,   .uart_rx_ready(rx_ready)
+                ,   .uart_rx_valid(rx_valid)
+                ,   .uart_rx_data(rx_data)
+
                 ,   .mem_command_ready(pdp_command_ready[i])
                 ,   .mem_command_valid(pdp_command_valid[i])
                 ,   .mem_command(pdp_command_data[i])
@@ -388,6 +491,34 @@ module top
                 ,   .led_link(local_led_link[i])
                 );
 
+            if (i == `NUM_PDPS-1) begin
+                assign tx_ready = rs232_tx_ready;
+                assign rs232_tx_valid = tx_valid;
+                assign rs232_tx_data = tx_data;
+
+                assign rs232_rx_ready = rx_ready;
+                assign rx_valid = rs232_rx_valid;
+                assign rx_data = rs232_rx_data;
+            end else begin
+                alt_jtag_atlantic
+                    #(  .INSTANCE_ID(1+i)
+                    ,   .LOG2_RXFIFO_DEPTH(10)
+                    ,   .LOG2_TXFIFO_DEPTH(10)
+                    ,   .SLD_AUTO_INSTANCE_INDEX("NO")
+                    ) uart
+                    (   .clk(internal_clock)
+                    ,   .rst_n(!internal_reset)
+
+                    ,   .r_dat(tx_data)
+                    ,   .r_val(tx_valid)
+                    ,   .r_ena(tx_ready)
+
+                    ,   .t_dat(rx_data)
+                    ,   .t_dav(rx_ready)
+                    ,   .t_ena(rx_valid)
+                    );
+            end
+
         end
 
     endgenerate
-- 
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