https://github.com/markmll/tang_nano_as_shipped

A close approximation of the demo code on Sipeed Tang Nano boards as shipped.
https://github.com/markmll/tang_nano_as_shipped

fpga verilog vhdl

Last synced: 15 days ago
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A close approximation of the demo code on Sipeed Tang Nano boards as shipped.

• Host: GitHub
• URL: https://github.com/markmll/tang_nano_as_shipped
• Owner: MarkMLl
• License: gpl-3.0
• Created: 2021-05-06T18:40:31.000Z (over 3 years ago)
• Default Branch: main
• Last Pushed: 2021-05-30T20:20:17.000Z (over 3 years ago)
• Last Synced: 2023-07-27T10:55:18.295Z (over 1 year ago)
• Topics: fpga, verilog, vhdl
• Language: Verilog
• Homepage:
• Size: 44.9 KB
• Stars: 4
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# tang_nano_as_shipped

A close approximation of the demo code on Sipeed Tang Nano boards as shipped.

/* When I wrote this, I had not been able to find the source of the bitstream */

/* which is preloaded onto the Sipeed Tang Nano "Little Bee" demo board (it   */

/* has since turned up, the link in Sipeed's documentation was broken). This  */

/* is notable for                                                             */

/*                                                                            */

/*       * Cycling its LEDs in the sequence off-G-B-R by sequencing each low  */

/*       * Cycle time is measured to be 4.19 seconds                          */

/*       * Low time for each LED is 1.048 seconds (4.192 / 4)                 */

/*       * Button B pressed (high) forces reset with all LEDs off (high)      */

/*                                                                            */

/* This is an attempt to reconstitute the missing project. It borrows heavily */

/* from https://github.com/andrsmllr/tang_nano_devbrd but chops out stuff     */

/* which isn't strictly necessary and attempts to indicate what imports (in   */

/* particular the clocks) actually are in terms of files.        MarkMLl      */ 


/* The LED signals could be conveniently redefined as a three-bit register.   */

/* I've left them like this since that's how they're defined in the donor     */

/* project, although I have corrected their order so that the sequence is the */

/* more conventional off-R-G-B, and used button A to reverse the sequence.    */


The serial interface chip on the Tang Nano board is underpowered, and grossly inadequate when plugged directly into a modern computer. Assume that for reliable operation you need a USB v1 hub, although many other cheap hubs have such poor performance that they might be suitable.

I can't speak for Windows, but on Linux you need to add (or enable the lines in) two additional configuration files before plugging the board in:

/etc/modprobe.d/tang-nano.conf

# Blacklisted to allow the Gowin programmer to run.


blacklist ftdi_sio


and

/etc/udev/rules.d/51-tang-nano.rules

# Remember to  udevadm control --reload  and to blacklist/remove the ftdi_sio the module.


KERNEL=="ttyUSB*", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6010", GROUP="plugdev", MODE:="0660"

SUBSYSTEMS=="usb", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6010", ATTRS{product}=="Sipeed-Debug", GROUP="plugdev", MODE="0660"

# NOTE: This illicitly uses an FTDI identifier, so should be left disabled.


If you don't have those, don't reload the udev rules, or don't remove ftdi_sio after adding/enabling the files, the Gowin programmer will attempt to run rmmod to remove ftdi_sio... this will of course fail for an unprivileged user.

So to wrap up, I say again: TWO configuration files, RELOAD udev, and REMOVE ftdi_sio.