Change implementation of SPI, add test bench, update docs

Author: hpretl

README.md

@@ -1,41 +1,9 @@
 ![](../../workflows/gds/badge.svg) ![](../../workflows/docs/badge.svg) ![](../../workflows/test/badge.svg) ![](../../workflows/fpga/badge.svg)
 
-# Tiny Tapeout Verilog Project Template
+# Simple SPI Test
 
-- [Read the documentation for project](docs/info.md)
+(c) 2024 Harald Pretl, Institute for Integrated Circuits, Johannes Kepler University, Linz, Austria
 
-## What is Tiny Tapeout?
+This project implements a simple SPI where the loaded 16b data can be output in 8b chunks (high and low byte). In addition, a magic cookie detection is implemented (an output goes active on detection of 0xCAFE).
 
-Tiny Tapeout is an educational project that aims to make it easier and cheaper than ever to get your digital and analog designs manufactured on a real chip.
-
-To learn more and get started, visit https://tinytapeout.com.
-
-## Set up your Verilog project
-
-1. Add your Verilog files to the `src` folder.
-2. Edit the [info.yaml](info.yaml) and update information about your project, paying special attention to the `source_files` and `top_module` properties. If you are upgrading an existing Tiny Tapeout project, check out our [online info.yaml migration tool](https://tinytapeout.github.io/tt-yaml-upgrade-tool/).
-3. Edit [docs/info.md](docs/info.md) and add a description of your project.
-4. Adapt the testbench to your design. See [test/README.md](test/README.md) for more information.
-
-The GitHub action will automatically build the ASIC files using [OpenLane](https://www.zerotoasiccourse.com/terminology/openlane/).
-
-## Enable GitHub actions to build the results page
-
-- [Enabling GitHub Pages](https://tinytapeout.com/faq/#my-github-action-is-failing-on-the-pages-part)
-
-## Resources
-
-- [FAQ](https://tinytapeout.com/faq/)
-- [Digital design lessons](https://tinytapeout.com/digital_design/)
-- [Learn how semiconductors work](https://tinytapeout.com/siliwiz/)
-- [Join the community](https://tinytapeout.com/discord)
-- [Build your design locally](https://www.tinytapeout.com/guides/local-hardening/)
-
-## What next?
-
-- [Submit your design to the next shuttle](https://app.tinytapeout.com/).
-- Edit [this README](README.md) and explain your design, how it works, and how to test it.
-- Share your project on your social network of choice:
-  - LinkedIn [#tinytapeout](https://www.linkedin.com/search/results/content/?keywords=%23tinytapeout) [@TinyTapeout](https://www.linkedin.com/company/100708654/)
-  - Mastodon [#tinytapeout](https://chaos.social/tags/tinytapeout) [@matthewvenn](https://chaos.social/@matthewvenn)
-  - X (formerly Twitter) [#tinytapeout](https://twitter.com/hashtag/tinytapeout) [@tinytapeout](https://twitter.com/tinytapeout)
+The input and output list documentation can be found in `info.yaml`.

info.yaml

@@ -18,24 +18,24 @@ project:
   # Don't forget to also update `PROJECT_SOURCES` in test/Makefile.
   source_files:
     - "tt_um_hpretl_spi.v"
-    - "chain1.v"
+    - "chain2.v"
 
 # The pinout of your project. Leave unused pins blank. DO NOT delete or add any pins.
 pinout:
   # Inputs
-  ui[0]: "clk (SCLK"
-  ui[1]: "data_in (MOSI)"
-  ui[2]: "select output byte (0 = low, 1 = high)"
-  ui[3]: ""
+  ui[0]: "SPI clk (SCLK)"
+  ui[1]: "SPI data in (MOSI)"
+  ui[2]: "SPI load (CS)"
+  ui[3]: "select output byte (0 = low, 1 = high)"
   ui[4]: ""
   ui[5]: ""
   ui[6]: ""
   ui[7]: ""
 
   # Outputs
-  uo[0]: "data_out (MISO)"
+  uo[0]: "SPI data out (MISO)"
   uo[1]: "cookie detected (loaded 0xCAFE)"
-  uo[2]: "XOR of clk and data_in"
+  uo[2]: "XOR of SPI clk and SPI data in"
   uo[3]: ""
   uo[4]: ""
   uo[5]: ""

src/chain1.v renamed to src/chain2.v

@@ -11,50 +11,60 @@
 
    IO description:
 
-    i_clk (like SPI SCLK)
-    i_dat (like SPI MOSI)
-    i_load (like SPI nCS)
-    o_dat (like SPI MISO)
+    i_clk (high running clock to sample the SPI input lines)
+    i_spi_clk (like SPI SCLK)
+    i_spi_dat (like SPI MOSI)
+    i_spi_load (like SPI nCS)
+    o_spi_dat (like SPI MISO)
     o_det (magic cookie detected)
     o_check (XOR of i_dat and i_load)
 */
 
-`ifndef __CHAIN1__
-`define __CHAIN1__
+`ifndef __CHAIN2__
+`define __CHAIN2__
 `default_nettype none
 
-module chain1 (
+module chain2 (
+    input wire          i_resetn,
     input wire          i_clk,
-    input wire          i_dat,
-    input wire          i_load,
-    output wire         o_dat,
+    input wire          i_spi_clk,
+    input wire          i_spi_dat,
+    input wire          i_spi_load,
+    output wire         o_spi_dat,
     output wire         o_det,
     output wire         o_check,
     output wire [15:0]  o_data
 );
 
     reg [15:0] scan_r, data_r;
+    reg last_spi_clk_r;
 
     // here we see if the stored content is matching a magic cookie
     assign o_det = (data_r === 16'hcafe) ? 1'b1 : 1'b0;
     // provide loaded data
     assign o_data = data_r;
     // shift out MSB register bit
-    assign o_dat = scan_r[15];
+    assign o_spi_dat = scan_r[15];
 
     // here the scan chain, shift MSB first (as in SPI)
-    always @(posedge i_clk) begin
-        if (i_load === 1'b0)
-            scan_r <= {scan_r[14:0],i_dat};
-    end
+    always @(posedge i_clk or negedge i_resetn) begin
+        if (i_resetn === 1'b0) begin
+            scan_r <= 16'b0;
+            data_r <= 16'b0;
+            last_spi_clk_r <= 1'b0;
+        end else begin
+            if ((i_spi_load === 1'b0) && (i_spi_clk === 1'b1) && (last_spi_clk_r === 1'b0))
+                scan_r <= {scan_r[14:0],i_spi_dat};
+
+            if (i_spi_load === 1'b1)
+                data_r <= scan_r;
 
-    // and here we latch the result
-    always @(posedge i_load) begin
-        data_r <= scan_r;
+            last_spi_clk_r <= i_spi_clk;
+        end
     end
 
     // here a very simple boolean function to check basic functionality
-    assign o_check = i_dat ^ i_load;
+    assign o_check = i_spi_dat ^ i_spi_load;
 
-endmodule // chain1
+endmodule // chain2
 `endif 

src/tt_um_hpretl_spi.v

@@ -4,7 +4,7 @@
  */
 
 `default_nettype none
-`include "chain1.v"
+`include "chain2.v"
 
 module tt_um_hpretl_spi (
     input  wire [7:0] ui_in,    // Dedicated inputs
@@ -20,13 +20,15 @@ module tt_um_hpretl_spi (
   wire [15:0] out_w;
 
   assign uio_oe = 8'b11111111;  // using IO for output
-  assign uio_out = ui_in[2] ? out_w[15:8] : out_w[7:0]; 
+  assign uio_out = ui_in[3] ? out_w[15:8] : out_w[7:0]; 
 
-  chain1 dut(
+  chain2 dut(
+    .i_resetn(rst_n),
     .i_clk(clk),
-    .i_dat(ui_in[0]),
-    .i_load(ui_in[1]),
-    .o_dat(uo_out[0]),
+    .i_spi_clk(ui_in[0]),
+    .i_spi_dat(ui_in[1]),
+    .i_spi_load(ui_in[2]),
+    .o_spi_dat(uo_out[0]),
     .o_det(uo_out[1]),
     .o_check(uo_out[2]),
     .o_data(out_w)
@@ -36,6 +38,6 @@ module tt_um_hpretl_spi (
   assign uo_out[7:3] = 5'b10000;
 
   // List all unused inputs to prevent warnings
-  wire _unused = &{ena, rst_n, uio_in[7:0], ui_in[7:3], 1'b0};
+  wire _unused = &{ena, uio_in[7:0], ui_in[7:4], 1'b0};
 
 endmodule // tt_um_hpretl_spi

test/Makefile

@@ -5,7 +5,7 @@
 SIM ?= icarus
 TOPLEVEL_LANG ?= verilog
 SRC_DIR = $(PWD)/../src
-PROJECT_SOURCES = project.v
+PROJECT_SOURCES = tt_um_hpretl_spi.v
 
 ifneq ($(GATES),yes)
 

test/tb.v

@@ -24,7 +24,7 @@ module tb ();
   wire [7:0] uio_oe;
 
   // Replace tt_um_example with your module name:
-  tt_um_example user_project (
+  tt_um_hpretl_spi user_project (
       .ui_in  (ui_in),    // Dedicated inputs
       .uo_out (uo_out),   // Dedicated outputs
       .uio_in (uio_in),   // IOs: Input path

test/test.py

@@ -1,17 +1,16 @@
-# SPDX-FileCopyrightText: © 2024 Tiny Tapeout
+# SPDX-FileCopyrightText: © 2024 Tiny Tapeout and Harald Pretl, IIC@JKU
 # SPDX-License-Identifier: Apache-2.0
 
 import cocotb
 from cocotb.clock import Clock
 from cocotb.triggers import ClockCycles
 
-
 @cocotb.test()
 async def test_project(dut):
     dut._log.info("Start")
 
-    # Set the clock period to 10 us (100 KHz)
-    clock = Clock(dut.clk, 10, units="us")
+    # Set the clock period to 0.1 us (10 MHz)
+    clock = Clock(dut.clk, 0.1, units="us")
     cocotb.start_soon(clock.start())
 
     # Reset
@@ -20,21 +19,65 @@ async def test_project(dut):
     dut.ui_in.value = 0
     dut.uio_in.value = 0
     dut.rst_n.value = 0
-    await ClockCycles(dut.clk, 10)
+    await ClockCycles(dut.clk, 3)
     dut.rst_n.value = 1
 
     dut._log.info("Test project behavior")
 
-    # Set the input values you want to test
-    dut.ui_in.value = 20
-    dut.uio_in.value = 30
+    # Check that cookie not detected
+    assert dut.uo_out.value[2] == 0
+    
+    # Load magic cookie
+    load_word = "0xCAFE"
+    load_word_bin = format(int(load_word, 16), '016b')
+    load_word_bits = [int(bit) for bit in load_word_bin]
+
+    dut._log.info("Loading " + str(load_word_bin))
+
+    # Shift cookie in
+    for i in range(16):
+        #b0 is clk, b1 is dat, b2 is load, b3 is select
+        dut.ui_in.value = 1*0 + 2*load_word_bits[i] + 4*0 + 8*0
+
+        await ClockCycles(dut.clk, 3)
+
+        #b0 is clk, b1 is dat, b2 is load, b3 is select
+        dut.ui_in.value = 1*1 + 2*load_word_bits[i] + 4*0 + 8*0
+
+        await ClockCycles(dut.clk, 3)
+
+        assert (dut.uo_out.value & 2) == 0
 
-    # Wait for one clock cycle to see the output values
+    # serial register is loaded, now store it
+     #b0 is clk, b1 is dat, b2 is load, b3 is select
+    dut.ui_in.value = 1*0 + 2*0 + 4*0 + 8*0
+    await ClockCycles(dut.clk, 3)
+    dut.ui_in.value = 1*0 + 2*0 + 4*1 + 8*0
+    await ClockCycles(dut.clk, 3)
+
+    # check magic cookie detection
+    dut._log.info("Check magic cookie detection")
+    assert (dut.uo_out.value & 2) == 2
+
+    # check output parallel selection
+    dut._log.info("Check parallel output")
+    dut.ui_in.value = 1*0 + 2*0 + 4*0 + 8*0
+    await ClockCycles(dut.clk, 1)
+    assert dut.uio_out.value == 0xfe
+    dut.ui_in.value = 1*0 + 2*0 + 4*0 + 8*1
     await ClockCycles(dut.clk, 1)
+    assert dut.uio_out.value == 0xca
+
+    # Shift 0 in
+    for i in range(16):
+        #b0 is clk, b1 is dat, b2 is load, b3 is select
+        dut.ui_in.value = 1*0 + 2*0 + 4*0 + 8*0
+
+        await ClockCycles(dut.clk, 3)
+
+        #b0 is clk, b1 is dat, b2 is load, b3 is select
+        dut.ui_in.value = 1*1 + 2*0 + 4*0 + 8*0
 
-    # The following assersion is just an example of how to check the output values.
-    # Change it to match the actual expected output of your module:
-    assert dut.uo_out.value == 50
+        await ClockCycles(dut.clk, 3)
 
-    # Keep testing the module by changing the input values, waiting for
-    # one or more clock cycles, and asserting the expected output values.
+        assert (dut.uo_out.value & 2) == 2