nanoball — Bouncing ball demo for Sipeed Longan Nano

Bart Massey 2020-03-11

This demo bounces a ball around the LCD screen of the Sipeed Longan Nano RISC-V embedded board.

Here's a video showing the code being developed.

The instructions below are for a reasonably current Debian Linux host. You are on your own for others.

Setup

Unplug your Longan Nano from USB if plugged in.

Install 99-ftdi.rules from this directory in /etc/udev/rules.d/ and run

udevadm control --reload-rules

cargo install cargo-binutils

rustup component add llvm-tools-preview

• Get the Rust compiler for this chipset.

You are then ready to build a binary.

cargo objcopy --release -- -O binary nanoball.bin

Now grab and install the Sipeed dfu-util from the link below. Sadly stock Debian dfu-util does not appear to work with this board.

Hook your Longan Nano to your box via USB and reset it by holding down the "BOOT" button, pressing and releasing the "RESET" button, then releasing the "BOOT" button. Now the Nano is ready to receive code, so sh dfuload.sh nanoball

• Hook your Longan Nano to your box via USB. The loader doesn't cope well with USB hubs, so hook directly to your host's USB.

• Reset the Longan Nano by holding down the "BOOT" button (the taller one in the standard case, on the right when USB port is at the bottom), then pressing and releasing the "RESET" button (the other one).

• Upload the demo.

    sh dfuload.sh nanoball
  

  You may need to power the Nano down and back up afterward.

Now the ball should be bouncing!

Debugging

You'll need a JTAG unit to get started with this. I'm using the Sipeed USB-JTAG/TTL RISC-V Debugger, which is about $8. Connect as follows:

 JTAG      Nano
 TDI       JTDI
 TMS       JTMS
 TDO       JTDO
 TCK       JTCK
 RXD       R0
 TXD       T0
 GND       GND

You'll also need a version of OpenOCD that supports the Nano's processor. Sadly, Debian's is not good enough: you'll want to build and install riscv-openocd.

Finally, you'll need gdb-multiarch or similar to actually do the debugging.

Once you have everything set up, get the Nano ready for upload as described at the beginning of this document (+BOOT,+RESET,-RESET,-BOOT). Then run sh openocd.sh. You should see openocd come up, give some mostly-meaningless errors, then attach to your Nano. Go to a separate terminal and run cargo run --release. You should now see gdb start up, upload nanoball.bin, and start it running. Hit ^C now to interrupt the running program. Gratz, you're debugging away!

Memory Size

There's an older version of the Longan Nano that has less memory. I doubt anyone has one anymore. Anyway, all the stuff to handle these is here, but will require some rewiring to access.

Resources

• https://dl.sipeed.com/LONGAN/platformio/dl-packages/

  tool-gd32vflash-v0.1.0-linux.tar.gz

• https://pramode.net/2019/10/07/rust-on-riscv-board-sipeed-longan-nano/

• https://blog.tonari.no/rust-simple-hardware-project