FSM-55

Intro

Having fun with LED matrices!

Getting Started

You have to clone the repository with the FSM-55 firmware first:

 git clone --branch cortex-m0-support git://git.gniibe.org/chopstx/chopstx.git

Second step is to install and configure a cross-compiler for the ARM Cortex-m0:

After configuring the cross-compiling environment, can compile the firmware by:

• Change to directory where we have the code examples:

 example-fsm-55/

• Create a symbolic link to the FSM-55 board:

 ln -s ../board/board-fsm-55.h board.h

• Compile the firmware:

 make

Now, we are ready to upload the firmware to the board, but first we need to connect the board to the JTAG programmer.

Connecting your board

To program the board, we need to use a programmer with support to the SWD protocol. The most common tool is the proprietary device from ST-Electronics, ST-Link v.2. We are not very happy with it, since it has a proprietary firmware. Tentatively, you could try to use a Bus Pirate, which is supposed to support SWD.

Usually, you just need two wires to connect your STM32: clock and data lines, but, for the FSM-55 we need the 'reset' line as well. So, here is the pinout:

Creating your message

The fun of this exercise is to create your own message and convert it to a C program.

The program is organized in three threads:

• LED thread (dynamic LED control)
• Button thread (watchdog)
• Application thread (text screen control)

The user does not need to change the low-level threads (LED and Button), only the Application thread. The data flows from Application -> (some sort of) Video RAM -> LED control

Messages are encoded in a 5 x 5 grid of LEDs. The 'led' thread loops through each column of 5x5 grid.

    -----
    -----
    -----
    -----
    -----

Each LED is addressed as such:

    - 0x00   * 0x00   * 0x00   * 0x00   * 0x00   * 0x00  
    -        -        *        *        *        *
    -        -        -        *        *        *
    -        -        -        -        *        *
    -        -        -        -        -        *

In other to present the message "Happy Hacking!" only the characters we use (including exclamation point and space) are described:

    { 3, 0 },                                             /* SPACE */
    { 4, DATA55V (0x1f, 0x04, 0x04, 0x1f, 0x00) },        /* H */
    { 3, DATA55V (0x17, 0x15, 0x0f, 0x00, 0x00) },        /* A */
    { 4, DATA55V (0x1f, 0x14, 0x14, 0x08, 0x00) },        /* P */
    { 4, DATA55V (0x19, 0x05, 0x05, 0x1e, 0x00) },        /* Y */
    { 4, DATA55V (0x0e, 0x11, 0x11, 0x0a, 0x00) },        /* C */
    { 4, DATA55V (0x1f, 0x04, 0x0c, 0x13, 0x00) },        /* K */
    { 3, DATA55V (0x11, 0x1f, 0x11, 0x00, 0x00) },        /* I */
    { 4, DATA55V (0x1f, 0x08, 0x06, 0x1f, 0x00) },        /* N */
    { 4, DATA55V (0x0e, 0x11, 0x15, 0x07, 0x00) },        /* G */
    { 2, DATA55V (0x1d, 0x1c, 0x00, 0x00, 0x00) },        /* ! */

The message is represented as a string:

    static uint8_t hh[] = {
         CHAR_H, CHAR_A, CHAR_P, CHAR_P, CHAR_Y,
         CHAR_SPC,
         CHAR_H, CHAR_A, CHAR_C, CHAR_K, CHAR_I, CHAR_N, CHAR_G,
         CHAR_EXC,
         CHAR_SPC, CHAR_SPC, CHAR_SPC,
    };

Authors

Gniibe is the author of the FSM-55. Unixjazz and Gniibe are the authors of this tutorial. It is released under CC-BY-SA-2.1 JP. Feel free to redistribute it and modify it for your needs.