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RZL1337 PRON-Wall Protocol Juli 2011
1 Introduction
This PRON-Wall Protocol (PWP) is defined to make available a datagram mode of
communicating with a series of dot matrix light panels working together to form
a display. This protocol assumes that the ethernet protocol [1] is used as the
underlying protocol.
This protocol provides a procedure for application programs to send messages
to light panels with a minimum of protocol mechanism. The protocol is
transaction oriented.
1.1 Terminology
A device connected to the network, with a unique MAC address.
A logical unit for displaying pictures. All Subpanels belong to a panel.
The set of panels logically connected to the same Ethernet segment.
The system that sends requests to the display (user equipment).
1.2 Hardware setup
A display has one ethernet interface (RJ45), power supply and two cinch sockets
to daisy chain the common interrupt line. Displays are addressed by their MAC
address (or via broadcast).
2 Communication
The following types of frames and packets are used for communication purposes.
The communication is structured into two parts: the first part deals with the
configuration of the panel devices and client software, the second part is used
for the actual image frame transmission and processing. All communication is
based on the Ethernet protocol.
2.1 Ethernet Frame
0 8 16 24 63
| T | V | S | R |
| Payload ...
T ... Packet type
V ... Version of the protocol (should be 23 for the first version)
S ... Subpanel ID
R ... Reserved
Ethertype: 0x2342
2.2 Packet Types
The first bit of the packet type defines whether is a request or reply.
0xxxxxxx ... request message
1xxxxxxx ... reply message
There are
0x00 ... Scan Request
0x80 ... Scan Reply
0x01 ... Echo Request
0x81 ... Echo Reply
0x02 ... Set Master Request
0x82 ... Set Master Reply
0x03 ... Frame
0x83 ... Frame Acknowledgement
2.2.1 Scan Request Payload
0 n
| R |
R ... Reserved
2.2.2 Scan Reply Payload
0 1 15 16 23 24 31 32 39
| REF | NSUBP | SUBPR | X1 |
| Y1 | ...
T ... Type of display (1 = RGB / 0 = Monochromatic)
BUFSZ ... Buffer size in frames of the panel
COLR ... Color of panel (Red value)
COLG ... Color of panel (Green value)
COLB ... Color of panel (Blue value)
REF ... Refresh rate of the panel (Hz)
NSUBP ... Number of subpanels in this panel
SUBPR ... Subpanels per row
X(1-N) ... Panel Width in pixels
Y(1-N) ... Panel Height in pixels
There are as many X,Y pairs as indicated in NSUBP. If NSUBP%SUBPR != 0, the last
row of subpanels consists of less subpanels than the other rows. "Color of
panel" could be used for identification in the client UI.
2.2.3 Echo Request Payload
0 8 16 24 32
| R | ID |
R ... Reserved
ID ... ID of the Echo Request. Should be returned by the other endpoint.
2.2.4 Echo Reply Payload
| R | ID |
R ... Reserved
ID ... ID of the Echo Request as sent by the client.
2.2.5 Set Master Request Payload
2.2.6 Set Master Reply Payload
| R | I |
R ... Reserved
I ... Feedback. 1 if the selected Panel is now the Master. 0 if not.
3 Master Autodiscovery
Upon bootup, a device waits at least one interrupt interval plus an additional
random backoff timer. If, during that time, no interrupt was recognized on the
input line, the device sets up an interrupt by itself and thus serves as the
master. Also, it informs the connected client about this decision so that
unlikely, but possible collisions (several masters) can be detected and
resolved by the client.
4 Image Frames
Each frame contains a single image with brightness levels. This image can either
be a greyscale image or one of the three base colors (R,G,B).
The protocol also supports 3D displays. The two most significant bits are
designated for those frames. The most significant bit marks frames that are part
of a 3D picture, the second one designates a frame for the left eye when it is
not set and for the right eye when set.
4.1 Image Frame
0 8 16 24 32
| C | TIME | SEQ |
| PIXELS ...
C ... type of frame (see 4.2)
TIME ... duration in milliseconds frame will be displayed
SEQ ... will be used for retransmissions
PIXEL ... each pixel is represented by a single byte, containing the
brightness level of this pixel
4.2 Image Frame Types
PWP supports monochromatic/greyscale, 3D and RGB frames. 3D can be achieved
using the shutter technique with an infrared LED serving as the synchronization
clock generator.
00xxxxxx ... normal frame
1xxxxxxx ... 3D frame
10xxxxxx ... 3D frame for left eye
11xxxxxx ... 3D frame for right eye
xxxxxx00 ... greyscale frame
xxxxxx01 ... red frame
xxxxxx10 ... blue frame
xxxxxx11 ... green frame
4.3 Sequence number
A sequence number designates the current full picture.</code>