This is the code for the LED-Torus (https://knielsen-hq.org/ledtorus.html).

It measures (using the hall-sensor) the speed of rotation of the PCB
and programs the TLC5955 LED drivers to output the 3D image at the
right timing. It also computes each frame of the animations displayed.
Optionally animations are read from an SD-card, if present. Also
optionally, input for interactive use is read from an nRF24L01+
wireless module, if present.

Following are some simple instructions for using the code with the
LED-Torus. In case of any questions please feel free to contact me at
Kristian Nielsen <knielsen@knielsen-hq.org>


Programming the LED-Torus.

The code runs on the STM32F405 MCU on the LED-Torus PCB. It can be
programmed using an ST-Link (or compatible) programmer. Connect the
3V3, SWC, GND, SWD (and optionally RST) pins on the 6-pin programming
header to the corresponding signals on the ST-Link.

The firmware should be written to the address 0x08000000 (when not
using an external bootloader which should be the normal use-case). The
included Makefile has a `make flash` target that does this using the
`st-flash` program, if available, but any flashing tool should work.

In the directory firmware/ are found a precompiled binary firmware
(.elf and .bin formats both supplied). These are tested to work and
can be used as an easy starting point before trying to compile own
firmware versions.

If all goes well, the LED-torus should start up and start flashing the
LEDs. The code outputs some debug info on the serial Tx output pin on
the debug header on the side of the PCB (115200 baud, one stop bit, no
parity).


Compiling the code

The code needs the ST Standard Peripheral Library for STM32F4x MCUs.
Version 1.6.1 is used, probably a later (or earlier) version will work
fine with few or no changes. This can be obtained from ST's website
(www.st.com).

The included Makefile can be used to compile the code with a standard
arm-none-eabi-gcc GCC compiler on posix-like systems. The path to the
ST library must be set to the correct location in the Makefile, and
then a simple `make` should compile the code.


Licence:

The LED-Torus code is copyright Kristian Nielsen. It is released under
the GPL, version 2 or later. Note that the LED-Torus code references
external libraries (eg. from ST Microsystems) which have different
licences.

If you would like to use the LED-Torus code under a different licence
than GPL then just contact me (knielsen@knielsen-hq.org), I'll
probably be willing to release under a different license as needed.