TangSketch 🎯

Write Arduino sketches for the Tang Nano 9K FPGA — running on a PicoRV32 RISC-V soft core.

No Arduino IDE setup hassle. Just install the board package, write setup() and loop(), and hit Upload.

void setup() {
    Serial.begin(115200);
    pinMode(LED_BUILTIN, OUTPUT);
    Serial.println("Hello from FPGA!");
}

void loop() {
    digitalWrite(LED_BUILTIN, LOW);   // LED ON  (active-low)
    delay(500);
    digitalWrite(LED_BUILTIN, HIGH);  // LED OFF
    delay(500);
    Serial.println("blink");
}

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Install in Arduino IDE 2.x

Step 1 — Add Boards Manager URL

File → Preferences → Additional Boards Manager URLs → add:

https://raw.githubusercontent.com/senolgulgonul/TangSketch/main/package_tangsketch_index.json

Step 2 — Install the board

Tools → Board → Boards Manager → search TangSketch → Install

Step 3 — Select board and port

Tools → Board → TangSketch → Tang Nano 9K (PicoRV32 / picotiny)
Tools → Port → your COM port (e.g. COM4)

Step 4 — Upload!

Click Upload — press S1 button on the board when prompted.

⚠️ Prerequisite: The picotiny SoC bitstream must be flashed to your Tang Nano 9K first using Gowin EDA. This is a one-time step.

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How It Works

Arduino sketch (.ino)
        ↓
riscv-none-elf-gcc  (-march=rv32i)
        ↓
RV32I binary
        ↓
upload.py  →  UART flash  →  Press S1
        ↓
PicoRV32 RISC-V CPU running inside GW1NR-9C FPGA

The Tang Nano 9K runs picotiny — a PicoRV32 RISC-V SoC synthesized into the FPGA fabric using Gowin EDA. TangSketch provides the Arduino-compatible layer on top.

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Prerequisites

1. xPack RISC-V GCC (must be in PATH)

Download: https://github.com/xpack-dev-tools/riscv-none-elf-gcc-xpack/releases/latest
Add bin/ to your system PATH.
Verify: riscv-none-elf-gcc --version

2. Python 3 + pyserial

pip install pyserial

3. picotiny bitstream on Tang Nano 9K

• Clone: https://github.com/sipeed/TangNano-9K-example
• Open picotiny/project/picotiny.gprj in Gowin EDA v1.9.12
• Synthesize → Place & Route → flash impl/pnr/picotiny.fs to embFlash
• This is a one-time step — firmware updates go over UART after this

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Supported Arduino Functions

Category	Functions
Digital I/O	pinMode, digitalWrite, digitalRead
Analog	analogWrite (software PWM, 8-bit)
Time	delay, delayMicroseconds, millis, micros
Math	abs, min, max, constrain, map, sq, random, randomSeed
Bits & Bytes	bit, bitRead, bitWrite, bitSet, bitClear, lowByte, highByte
Characters	isDigit, isAlpha, isAlphaNumeric, isUpperCase, isLowerCase, isSpace, isPrintable
Advanced I/O	shiftOut, shiftIn, pulseIn
Serial	Serial.begin, Serial.print, Serial.println, Serial.write, Serial.read

⚠️ Key Differences from Standard Arduino

	Arduino	Tang Nano 9K
LED logic	Active HIGH	Active LOW — LOW = ON, HIGH = OFF
ADC	analogRead() available	❌ No ADC hardware
I2C / SPI	Wire, SPI	❌ Not in picotiny SoC
Tone	tone()	❌ Not available

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Example Sketches

The arduino/ folder contains ready-to-use examples:

Sketch	Description
sketch_blink.c	LED blink every 500ms
sketch_knight.c	Knight Rider scanner on 6 LEDs
sketch_counter.c	Binary counter 0–63 on 6 LEDs
sketch_random_leds.c	Random patterns using random() and millis()
sketch_fade.c	PWM fade using analogWrite()

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Hardware

Board	Sipeed Tang Nano 9K
FPGA	Gowin GW1NR-9C (8640 LUT4)
CPU	PicoRV32 RV32I soft core @ 25.175 MHz
LEDs	6 × active-low (pins 0–5)
Buttons	S1 = reset / ISP trigger, S2 = GPIO
UART	115200 baud via BL702 USB bridge
Flash	32Mbit SPI flash (7MB available for firmware)

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Repository Structure

TangSketch/
├── arduino/                  ← Standalone compile tools + sketches
│   ├── picotiny_hal.h        ← Arduino HAL (for command-line use)
│   ├── crt.S                 ← Startup assembly
│   ├── sections.lds          ← Linker script
│   ├── make_flash.py         ← Command-line build tool
│   └── sketch_*.c            ← Example sketches
├── bsp/                      ← Arduino IDE Board Support Package
│   └── hardware/tangsketch/avr/
│       ├── boards.txt
│       ├── platform.txt
│       ├── cores/picotiny/   ← Arduino.h + main.cpp
│       ├── variants/tangnano9k/
│       └── tools/pico_programmer/
├── package_tangsketch_index.json  ← Boards Manager index
└── README.md

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Credits

• Sipeed — picotiny PicoRV32 SoC for Tang Nano 9K
  https://github.com/sipeed/TangNano-9K-example
• YosysHQ — PicoRV32 RISC-V CPU core
  https://github.com/YosysHQ/picorv32
• Gowin Semiconductor — GW1NR-9C FPGA & EDA tools

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Author

Senol Gulgonul — @senolgulgonul

If TangSketch helped you, give it a ⭐ and share it!

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License

MIT License — free to use, modify, and share.