Version "V2" Firmware Upgrade for the GTOCP3

Version V2 is anticipated to be the last upgrade for the GTOCP3 control box. All further upgrades will be available only for the GTOCP4 control box. The GTOCP4 has faster processing speed and increased memory capacity for future feature additions. Since the GTOCP4 can be updated via internet download, future revisions can be accomplished more rapidly. If you are considering an upgrade to the V2 chip and are not eligible for a free upgrade, we suggest that you consider upgrading to the GTOCP4.

The EEPROM of the GTOCP3 must have at least version "V" firmware in order to download and use our Astro-Physics Command Center (APCC) software. It contains many new commands needed for the advanced features of APCC, including custom absolute tracking rates implemented in arc seconds per hour and new meridian delay commands/ functions and safety features to name a few.

Determine your Current ROM Chip Version

There are several ways to check the version letter and date of the microprocessor ROM chip to see if you already have a"V2" version chip.

How does the "V2" Chip Differ From the Chip I Currently Have?

Refer to Revisions to ROM chip of the GTOCP3 Control Box (PDF).


Please refer to the information below to determine the pricing for your chip upgrade.

All mounts with Absolute or Precision Encoders (only applies to 1100, 1600 and 3600 mounts with these encoders installed)
The V2 chip is a free upgrade for these mounts since it provides improved autoguider performance. The chip upgrade kit (part # CHIPKITV2) includes the "V2" version chip, extraction tool and installation instructions. We will also provide the most recent chip for the GTOAE and GTOELS Control boxes, at no charge, if needed. Please refer to the order information below.

All other mounts with GTOCP3 control boxes
The price for the chip upgrade kit (part # CHIPKITV2) is $92 plus shipping. The kit includes the "V2" version chip, extraction tool and installation instructions. Please refer to the order information below.

Installation Options

You may choose to install the chip yourself using these instructions or send the control box to Astro-Physics. There is an additional installation charge of $45 plus return shipping.

Important Considerations if you are upgrading from "Q" or earlier version.

If your previous ROM chip was version "Q" or earlier, you MUST perform a full initialization on your first power-up, and you will also need to redo the mount's PEM (Periodic Error Memory). To accommodate the added features of these newer chips, the location in the GTOCP3's non-volatile memory where time, location, gear angle and PE information is permanently stored has been changed. Your previously stored data will no longer be usable. The new information you enter now, however, will be remembered going forward.

Initialization: If you use the keypad in your first session, follow the instructions in the Keypad Manual as if you are setting up for your first session. You will not have to setup your location data or time since that information is stored in the keypad.

If you control your mount with a PC in your first session (i.e. with the ASCOM Driver, APCC, PulseGuide or any other computer control), be sure that the options are selected to send all of the time, date, GMT offset and location data to the mount. For your first time using the new ROM chip your computer software MUST give the servo a full initialization. You will also need to reestablish pointing and orientation by resuming from one of the AP pre-defined park positions or by performing a Sync on a star. Note: a Re-Calibrate is not sufficient.

PEM (Periodic Error Memory): You will need to redo your PEM. Since the gear angle information is lost, the PE data that you have stored will no longer be in sync with the worm gear, so simply saving it to your computer via PEMPro and reloading it will not work. Once new PEM data is stored with the correct gear angle association, it will be remembered going forward.

Order Information

These instructions apply to all CHIPKITV2 upgrades.

Order Version "V2" Firmware
Who may order:

Part # to order: CHIPKITV2, which includes "V2" chip, extraction tool and instructions

How to order:
Contact Astro-Physics directly or designated dealer mentioned above. You must provide the following information:

Upgrade to GTOCP4 Control Box
If you currently have a GTOCP3, you may wish to upgrade to a new control box. Please return to and search on GTOCP4 to order.

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This page was last modified: June 20, 2023

Astro-Physics, Inc.
11250 Forest Hills Road, Machesney Park, IL  61115, U.S.A.
Phone: 815-282-1513   Fax: 815-282-9847