MCMTII

MCMTII

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 1.2.3.8. 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.

Implementing the library for POSIX systems

The obvious choice would be to code a portable (POSIX) C library. However, it must be considered that the right choice is not the obvious choice, but the most useful choice. Is it better to write a library or an API? If it's an API, in what programming language? Software that will be using the library must be studied before starting to write crazy things.

RS232 protocol

The protocol for the serial link is quite simple, based on request-response exchanges. Is it the LX200 protocol? How does it differ from it?

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 the ascii value of a letter. We will now see the list of special commands, separated in two: the list of setup commands, and the list of runtime command.

Bytes from the response buffer are referenced as {i} where i is the i^th byte. PEC is periodic error correction. KING is a method for refraction compensation by offsetting the telescope pointing.

Special commands for telescope operation mode

Command	Request	Response
from RetrieveData AlphaDelta_Internal, get step values for PEC	'r', 0, 0, 0, 0	10 bytes, containing as follows:
		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}, boolean value indicating if parked
from RetrieveData AlphaDelta_Internal, update current speed (or stop moving)	'R', {3 bytes (same format than 3 first bytes of 'r' reply)}	none
from RetrieveData AlphaDelta_Internal, activate PEC	'L', 2F, activate?1:0, 0, 0	none
from RetrieveData AlphaDelta_Internal, erase PEC	'e', 0, 0, 0, 0	none
from RetrieveData AlphaDelta_Internal, save PEC	'E', 0, 0, 0, 0	none
from TelescopeMoveAxe, move number of steps	'p', {4 bytes of int32 number of steps}	none
from MoveTelescope, north or west move max speed	'X', 0, 0, 0, 0	none
from MoveTelescope, north or west move medium speed	'G', 0, 0, 0, 0	none
from MoveTelescope, north or west move min speed	'D', 0, 0, 0, 0	none
from MoveTelescope, south or east move max speed	'W', 0, 0, 0, 0	none
from MoveTelescope, south or east move medium speed	'F', 0, 0, 0, 0	none
from MoveTelescope, south or east move min speed	'Q', 0, 0, 0, 0	none
from Stop_Telescope, stop moving, resume sideral speed	'S', 0, 0, 0, 0	none
from STOP_ALL_Telescope, move to parking position	'P', 0, 0, 0, 0	none
from ReturnToSideralSpeed, no park mode	'N', 0, 0, 0, 0	none

Special commands for telescope setup mode

Command	Request	Response
loading setup (read from MCMTII's EEPROM)	'K', 0, 0, 0, 0	48 bytes, containing as follows:
		{1..3} is guiding speed
		{4..5} is correction P speed
		{6..7} is correction M speed
		{8..9} is point L
		{10..11} is point R
		{12} is acceleration
		{13} is boolean for inversion
		{29..30} is the resolution
saving setup (write to EEPROM)	'L', setup command ID, data ...	none
get MCMTII's version	'V', 0, 0, 0, 0	a string up to 80 characters
flash EEPROM (put device in special programming mode)	'M', 0, 0, 0, 0, followed by data:	none
	dev_id (initialize transfer)	EB (IDACK)
	E3 (WRITEBOOT), address high, address low, length (10), checksum, {10 bytes data}	E7 (DATA_OK), E4 (WOK) (success)
	ED (DONE), {whatever?}	E4 (WOK) (success)

For setup command IDs, see procedure TSetupTelescope.Button_EcrireClick in Setup.pas. Speeds, precisions and corrections are set using these commands.