Revision as of 04:53, 29 August 2012 by Vincent (talk | contribs) (RS232 protocol: some commands from the protocol)


Link to official webpage (in French).

Recent versions (2011) of the MCMTII, which have undergone a few evolutions since MCMTII has been described on the website, only work with the non-free PRISM software (for windows) in versions 7 or 8 or the Ascom driver.

The current source available from the download page is quite old. Here is a local copy of this file, version A newer version will be requested soon as well as protocol documentation. It is developed by Alcor System, so does PRISM. The code in Delphi language for Windows.

RS232 protocol

The protocol for the serial link is quite simple, based on request-response exchanges. The windows DLL opens and closes the serial port for each write and read operation.

Three types of messages exist, as explained in the following table. axis_id is `E0' for alpha axis (right ascension), `E1' for delta axis (declination). In the fields request and response of the table, values or identifiers represent bytes, and they are separated by commas. Comments are between parentheses.

Command Request Response
device ready axis_id, FF 01 (success value)
read encoder axis_id, F1 + byte number [0..3] the requested byte from the int32 value
special command axis_id, {7 bytes maximum for the command} 06, {data} (if response data is available)

Most commands then fall into the special command category. Data is mostly ascii text, and commands start with an identifier, which is generally a letter. Bytes from the response buffer are referenced as {i} where i is the ith byte. PEC is periodic error correction. KING is a [method for refraction compensation by offsetting the telescope pointing]. The following table lists these commands (to be completed).

Command Request Response
from RetrieveDataAlphaDelta_Internal, get step values for PEC 'r', 0, 0, 0, 0 (10 bytes): current speed steps per second = 625000 / {3} / 10 + {2} + 256 * {1} ; index PecC = {4} ; Pec step = 256*{5} + {6} ; another step value? 256*{7}+2*{8} ; Panel info pec = {9} & 0F ; Pec state 1 = {9} ; Pec state 2 = {10}
from RetrieveDataAlphaDelta_Internal, update current speed 'R', {3 bytes (same format than 3 first bytes of 'r' reply)} none
from RetrieveDataAlphaDelta_Internal, activate PEC 'L', 2F, activate?1:0, 0, 0 none
from RetrieveDataAlphaDelta_Internal, erase PEC 'e', 0, 0, 0, 0 none
from RetrieveDataAlphaDelta_Internal, save PEC 'E', 0, 0, 0, 0 none