MicroControllerUnitFrameEnglish

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Stream

The microcontroller unit frame protocol is used to transmit grayscale or colored Blinkenlights streams using UDP packets. Simply, a UDP packet is sent for every new frame (frames lasting more than one second are repeated every second, 5 seconds is the stream timeout):

+-----------------------+
| magic                 |
| 0x23 0x54   0x26 0x66 |
+-----------+-----------+
| height    | width     |
| 0x00 0x14 | 0x00 0x1A |
+-----------+-----------+
| channels  | maxval    |
| 0x00 0x01 | 0x00 0xFF |
+-----------+-----------+
| pixels                |
| 0xFF 0xCC   0x99 0x66 |
| 0x33 0x00   0x00 0x00 |
| ...                   |
| 0x00 0x00   0x00 0x00 |
+-----------------------+

• magic: fixed value
• height: the height of the image in pixels
• width: the width of the image in pixels
• channels: the number of channels of the image, 1 for grayscales, 3 for RGB
• maxval: the maximum pixel value used in the pixel data
• pixels: the value of the channels * width * height pixels
  • 0 for off, maxval for on, values between 0 and maxval for grayscales
  • from left to right, then from top to bottom (i.e. channels of top left pixel first, pixel right to it next, ...)
• all values are in network byte order - big endian - highbyte first

The UDP port should be configurable at server and client side. The standard port is UDP 2323.

It is also possible to send those packets over stream-like connections, like TCP or serial ports.

Dynamic Extension

The dynamic extension can be used to request a MCUF stream dynamically. A request packet is sent periodically (every 10s) to the UDP port of the server. The server then replys with a MCUF stream sent from this port to the source port of the request packet. After no request packet has been received for a longer time (30s), the stream is no longer sent. This dynamic extension is also known as the Blinkenproxy protocol.

The format of the request packet is as follows:

+-----------------------+
| magic                 |
| 0x42 0x42   0x42 0x42 |
+-----------------------+
| reserved              |
| 0x00 0x00   0x00 0x00 |
| 0x00 0x00   0x00 0x00 |
+-----------------------+

• magic: fixed value
• reserved: fixed value for now

It is also possible to tell the server that the stream is no longer needed. This happens by sending a close packet instead of a request packet:

+-----------------------+
| magic                 |
| 0x42 0x42   0x42 0x43 |
+-----------------------+
| reserved              |
| 0x00 0x00   0x00 0x00 |
| 0x00 0x00   0x00 0x00 |
+-----------------------+

• magic: fixed value
• reserved: fixed value for now

Additional Information

A further extension allows to transmit information in addition to the stream packets or the request packets of the dynamic extension. Those information packets have the following structure:

+-----------------------+
| magic                 |
| 0x42 0x42   0x42 0x23 |
+-----------------------+
| info                  |
| 0x45 0x4E   0x44 0x00 |
| 0x00 0x00   0x00 0x00 |
+-----------------------+

• magic: fixed value
• info: 0..8 ASCII characters, padded with 0x00 to 8 bytes in total
  • "END", S2R: the stream has ended
• abbreviations:
  • S2R: sender to receiver, packet is sent in same direction as stream frames
  • R2S: receiver to sender, packet is sent in same direction as stream requests