From e0970b34d629eb765e6e488f6c43caef1620faf3 Mon Sep 17 00:00:00 2001
From: uvok
Date: Tue, 23 Dec 2025 19:37:13 +0100
Subject: Add FPGA basics

---
 .gitignore |  4 ++++
 Makefile   | 19 +++++++++++++++++++
 led.v      | 28 ++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 led.v

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..15fc2c5
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+*.json
+*.cst*
+*.fs
+
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..949996d
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,19 @@
+all: led.fs
+
+tangnano9k.cst:
+	wget https://github.com/YosysHQ/apicula/raw/refs/heads/master/examples/tangnano9k.cst || \
+	curl -LO https://github.com/YosysHQ/apicula/raw/refs/heads/master/examples/tangnano9k.cst
+
+led.json: led.v
+	yosys -p "read_verilog led.v; synth_gowin -top led -json led.json"
+
+pnrled.json: tangnano9k.cst led.json
+	nextpnr-himbaechel --json led.json --write pnrled.json \
+	--device GW1NR-LV9QN88PC6/I5 --vopt family=GW1N-9C \
+	--vopt cst=tangnano9k.cst
+
+led.fs: pnrled.json
+	gowin_pack -d GW1N-9C -o led.fs pnrled.json
+
+flash: led.fs
+	openFPGALoader -b tangnano9k -f led.fs
diff --git a/led.v b/led.v
new file mode 100644
index 0000000..772415f
--- /dev/null
+++ b/led.v
@@ -0,0 +1,28 @@
+module led (
+    input clk,              // clk input
+    input rst_i,              // reset input
+    output reg [5:0] led    // 6 LEDS pin
+);
+
+reg [23:0] counter;
+
+always @(posedge clk or negedge rst_i) begin
+    if (!rst_i)
+        counter <= 24'd0;
+    else if (counter < 24'd1349_9999)       // 0.5s delay
+        counter <= counter + 1'b1;
+    else
+        counter <= 24'd0;
+end
+
+always @(posedge clk or negedge rst_i) begin
+    if (!rst_i)
+        led <= 6'b111110;
+    else if (counter == 24'd1349_9999)       // 0.5s delay
+        led[5:0] <= led[5:0] - 1;
+    else
+        led <= led;
+end
+
+endmodule
+
-- 
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