Mount Connection Details
Contents
Connection options for the AP V2 ASCOM Telescope Driver have expanded greatly with the introduction of the GTOCP4 control box. The expanded options include serial/USB, Ethernet and WiFi to the connections possibilities. More options means more potential benefits, but it also means that you now have choices to make regarding the best connection method for your setup. Please see the relevant sections of the GTOCP4 or GTOCP5 manual for more information. We'll address these options as a group of questions and answers.
•First Decision Point: ASCOM only or ASCOM and APCC? Will you be using the Astro-Physics Command Center (APCC), or will the driver be your sole intermediary between your external software and the mount? If you will be using APCC, do nothing further in the AP V2 driver's Mount Connection Details group box. Setup your connection details from within APCC for both itself and the driver. If you wish to use only the ASCOM V2 driver (without APCC) proceed to the second decision point:
•Second Decision Point: If ASCOM only, what is the physical mount connection? For ASCOM driver-only connections (NO APCC), how do you want to physically connect to the mount: Do you want to use an IP-based connection (Ethernet or WiFi) or serial based connection (RS232 serial or USB)? If you aren't yet sure which to use, here are some helpful hints.
oIn terms of basic operation of the mount, plain, old-fashioned serial (i.e., RS232 DB9 connector) is as a solid choice. It is reliable, simple, and plenty fast enough for mount communications, even at 9600 baud. Its main 'shortcoming' is a misconception that a serial connection is "not up to the task". We assure you, it is. USB is also basically serial, but it has increased speed and bandwidth beyond what the AP GTO system requires. USB's primary advantages are ease of use, compatibility with modern computer connections, and the GTOCP4 & 5's FTDI Virtual Com Port (VCP) is the best USB/serial device on the market.
oIn operational terms, WiFi and Ethernet are nearly identical. The only difference is the medium through which the data or commands move. Ethernet connects via twisted pair copper wire. WiFi does the same thing through thin air over radio waves. WiFi is perfect for portable setups. Ethernet is preferred for permanent observatory setups. WiFi has the advantage of one less cable (always a good thing) but is subject to possible interruptions due to signal loss or other interference.
oUsing USB or serial sets you up to take advantage of the Astro-Physics USBserial Utilities program. You can still use the utility when communicating over IP, but you will still need to set up the serial connection to use it.
•The two decision points above, each with its own pair of options gives the 4 options we will describe below.
IMPORTANT SIDE NOTE for GTOCP1, 2 & 3 OWNERS: The two RS-232 serial ports on the GTOCP4 & 5 are identical for all practical purposes. However, the two RS-232 serial ports on the GTOCP1, 2, and 3 control boxes are NOT identical. There are two universal asynchronous receiver/transmitters, or UART devices that control serial communication in the GTOCP1, 2 & 3.
• Top RS-232 and Keypad serial ports: The primary UART is built into the EPROM chip that is the microcontroller “brains” of your mount. It is in fact a dual UART and it serves both the top RS232 port and the Keypad receptacle. This is why all keypad firmware updates must be done through the top port of the GTOCP3.
• Lower RS-232 serial port: The second UART is found on a field programmable gate array (FPGA chip) in the control box. While this UART is suitable for many applications, it does have certain limitation vis-à-vis the primary UART. Of particular concern to users of high demand (or high traffic) software, including the ASCOM V2 driver, is the lower over-sampling ratio in the second UART. This makes the lower RS232 port more susceptible to framing errors due to noise, differences in the number of start bits, baud rate mis-matches, etc.
The issue with the lower RS-232 port is not really a problem with either the port’s UART or the ASCOM V2 Driver, both of which work as they should. It is instead related to the PC hardware, and possibly how the operating system or system services are configuring it. The port selection is, however, the only aspect of this that we as end users have any control over.
The Easy, 4-Option Mount Connection: The options are selected using the drop-down list just below the group-box header. The first two options are for driver-only installations. The last two options are for connecting through APCC. Note also that Option #2 (ethernet/wifi connection) is NOT available for the GTOCP1, 2, or 3. In addition: GTOCP3 users who use APCC will need APCC v.1.9.6.x or later + AP V2 v.5.60.00 or later to use the REST API. Read on for the details:
Option 1: COM PORT (NO APCC) This setting is appropriate when you do not want to use APCC and wish to connect to your mount via a serial connection (USB or DB9 serial). This is the default setting and what you will see in a brand new installation of the driver. It is also presented here in its proper place on the Setup-window. Remember that for our purposes USB is the same as Serial. 1.Check all serial cables and connections 2.Power control box ON 3.Click the Find Mount button. The driver will seek out your mount and display it for you. Note that it will also find any other AP mounts on your PC. Select the correct mount. 4.Click the Check Port button. If all is OK, you will see a successful connection to the mount evidenced by the displayed firmware version. Option 2: IP CONNECTION (NO APCC). This setting is appropriate when you do not want to use APCC and wish to connect to your mount via Ethernet or WiFi. 1.Check all cables and connections 2.Power mount ON. 3.Use the FindMounts utility to find the control box's Hostname/ IP address: 4.Enter resulting Hostname or IP address. We recommend using the IP address instead of hostname 5.After connecting, you can confirm successful connection to the mount evidenced by the firmware version of the control box. Option 3: CONNECT VIA APCC AND REST API This setting is appropriate when you wish to use APCC via the REST API. This is our recommended and preferred connection option and provides a simple connection between the client software and APCC. The only connection settings here are to choose this option. The additional mount connection options are set up with the APCC program.
For full instructions, please see the APCC Help documentation: Setting up the Astro-Physics V2ASCOM Driver Option 4: CONNECT VIA APCC AND Virtual COM Ports This setting is appropriate when you wish to use APCC via a Virtual Com Port. This is a second option to connect to APCC instead of the REST API. This option is primarily for fringe cases and legacy users. You should use the REST API to connect to APCC unless you have a specific reason that prevents you from using the REST API.
For full instructions, please see the APCC Help documentation "Setting up the Astro-Physics V2ASCOM Driver" Additional Information: Port: The COM port on which the driver will attempt to communicate with the mount. Please note that this refers to the computer COM port as defined by the Windows Device Manager. It does not refer to either of the ports on the GTOCPx Control Box. Timeout: the number of milliseconds to wait before retrying a command. Usually the mount will respond in less than 100 milliseconds so we recommend you start with 100 or 200 msecs. If you experience timeouts try increasing this timeout value. A higher timeout value will decrease the responsiveness of the driver so it's best to find the shortest value that gives you no timeout errors. Retry count: the number of retries before a command is considered failed. We recommend that you start with a value of 2 with the goal of setting it back to 1 or 0 after the system is commissioned and running smoothly. Multiple retries can decrease the responsiveness of the driver if there are communications problems, so solve those first before reducing the retry count. Check Port: press this button to detect if the mount is connected on the COM port. Please note: The mount must be powered up for the driver to receive a response. The mount does not need to be initialized yet. If the query to the mount is successful the mount's firmware version will be displayed. Timeouts: When the COM port is set to an APCC virtual ports, command/response exchanges between the driver and APCC usually require a much higher timeout (1000-5000 msecs). APCC optionally can set the timeout in the appropriate range but if you experience timeouts try increasing the timeout period. |
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