Alpha 215C Protocol

In the past, we were mostly left with experimentation and information discovered on the net. As such, this document is not necessarily complete or correct.

Someone got me started with this fragment of QBASIC code which I ran on NT:

10 OPEN "COM1:9600,E,7,,CS,DS,CD" FOR RANDOM AS #1
20 FOR I = 1 TO 20: PRINT #1, CHR$(0); : NEXT I
30 PRINT #1, CHR$(1) + "Z00" + CHR$(2) + "AA" + CHR$(27) + " b" + "Message" + CHR$(4)

Communication Settings

Timing

Wake Up Sequence

The odd part is that it seems you can use any character. The goal appears to be sending enough characters, which happen to be thrown away by the sign, so that it can determine the baudrate. This can be demonstrated by creating a for loop that wakes the sign with different characters.

It appears that a minimum of about 5 nuls are needed to sync the baudrate. However, once the sign has detected a new baudrate, you can get away with less.

0x01 is "start of header" [see an ASCII chart]
So we can conclude that a sequence of 0x00 or 0x01 is the best choice. Anything other than that might be taken as data, and 0xFF is out because the high bit is used for parity.

Sign Identification

Working backwards, I'm guessing that 00 stands for all signs as it does with the Prolite Protocol.

If the value is 00, then no matter what the sign ID is, the sign responds. If the value is non-zero, it must match the sign's programmable id.

The 'Z', on the other hand, appears to identify the kind of sign in some way. This, again, can be seen by making a FOR-loop and testing all the values from 0 to 255:

Sending this...	Shows the message. (Here's a guess as to the meaning.)
'!'	Reports "Transmission Error" but in a moment shows the message.<
'1'	Possibly one line signs?
'?'	All signs?
'Z'	All signs?
'f'	Just the 215C? Does this work for any other models?
'z'	All signs?
0xA1	Reports "Transmission Ok" but in a moment shows the message.
0xB1'	Same as '1'? Possibly one line signs?
0xC0	Same as '?'? All signs?
0xDA	Same as 'Z'? All signs?
0xE6	Same as 'f'? Just the 215C? Does this work for any other models?
0xFA	Same as 'z'? All signs?
It appears these are the same values, just with the high bit on. This makes sense, given we're using Even parity to talk with the sign, the 8th bit wouldn't be used. Additionally, it's curious the parity bit changes the behavior of the '!' message.

Text Part

I'm not quite sure what the "AA" +CHR$(27) +" b" (aye aye escape space bee) is doing.

After that it appears that you can have text until you get to 0x04 is "end of transmission". [see an ASCII chart]

The sign does not seem to care if there is a cr/lf sequence ending the request or not.

Sending Text

Message Display Modes

I have not figured out how to change the message display mode in midstream of a message yet.

You might want to compare these with the Pro-Lite Display Effects.

Byte Used	Display Message Effect
'a' 0x61	Regular smooth scroll, right to left
'b' 0x62	Appear. Centers as much of message on screen, waits, and displays rest of message in similar manner
'c' 0x63	Appear with flashing.
'd' 0x64	Auto. Randomly picks an effect for each part of the message, as opposed to the message as a whole.
'e' 0x65	Scroll up.
'f' 0x66	Scroll down from top.
'g' 0x67	Jerky scroll from right to left.
'h' 0x68	Jerky scroll from left to right.
'i' 0x69	Wipe up from bottom, covering text.
'j' 0x70	Wipe down from top, covering text.
'k' 0x71	Wipe over from right to left, character by character, not by pixels.
'l' 0x72	Wipe over from left to right, character by character.
'm' 0x73	Scroll up. Same as 'e'?
'n' 0x74	This is doing something weird based on message itself. Will have to investigate.
'o' 0x75	Auto/Random (same as 'd'?)
'p' 0x76	--> CENTER <-- Text appears at sides and squishes content in.
'q' 0x77	<-- CENTER --> Text splits in center and pushed content out.
'r' 0x78	--> COVER <-- New text covers old out to in.
's' 0x79	<-- UNCOVER --> New text uncovers in to out.
't' 0x80	Compressed text! Using this mode the sign tricks your eyes into seeing more characters than it is capable of physically producing. Scrolls right to left.
'u' 0x81	Fast Appear.
'v' 0x82	Medium Appear.
'w' 0x83	Maybe medium-slow appear.
'x' 0x84	Same as 'p'?
'y' 0x85	Same as 'q'?
'z' 0x86	Same as 'r'?
'@' 0x40	The sign went blank.
It is interesting to note that during Auto/Random mode, the sign produces more effects than are shown in the above table. This suggests that mode 'n' is doing something freaky, since the message seems to somehow control what happens.

I ran the whole character set through, and all of the unique modes appear in the subset above. One point of interest was when I sent 0x13 to the sign in the message, the time appeared.

It would seem that there are binary codes that expand to macros within the sign.

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