| 0,0 → 1,125 |
|---|
| EQ-6/Atlas handpaddle protocol (v3 - 11 Jan 2004). |
| |
| Darren Hutchinson |
| dbh@gbdt.com.au |
| |
| $Id: eq6-serial.txt,v 1.3 2004/03/07 07:44:59 dbh Exp $ |
| |
| Introduction: |
| |
| The EQ-6/Atlas hand controller is used to control the operation of the |
| Atlas/EQ-6 mount. The hand controller also acts as a power switch for |
| the mount. |
| |
| The communication bewteen the controller and the mount is |
| unidirectional, with data being sent from the controller to the mount |
| over a single wire. The other wires provide ground, +12V from the mount |
| to the controller, and switched 12V back to the mount. |
| |
| Cable pinout TBD. |
| |
| Physical format: |
| |
| The signal is a 0/5V signal, with a '1' represented by 5 V. Start bits |
| are '0', stop bits are '1' |
| |
| Data format: |
| |
| The data is a set of 6 asynchronous words with a format of 1 start bit, |
| 9 data bits, and 1 stop bit. The bits are transmitted at rate of 935 |
| bits per second. The six words are transmitted every 76.2 ms. |
| |
| Note that there is no indication in the data of which word is actually |
| the first in the set of words. The ordering below is a guess based on |
| the distribution of extra stop bits in the set of words. |
| |
| The distribution of extra stop bits between the six words depends on |
| which keys are pressed but it seems unlikely that this is detected or |
| used by the mount. |
| |
| The six words are divided into two sets of three, one set for RA, the |
| other for DEC. Each set contains a sync word, a direction word, and a |
| speed word. |
| |
| All words below are shown with the most significant bit on the left. The |
| least significant bit is transmitted first, immediately after the start |
| bit. All RA words have bit 8 set to 0, all DEC words have bit 8 set to 1. |
| |
| Word 1: RA sync |
| |
| This word is always the bit pattern 001111110 (0x07e). |
| |
| B0: Always 0 |
| B1 - B6: Always 1 |
| B7 - B8: Always 0 |
| |
| Word 2: RA direction |
| |
| This word determines the rotation direction of the RA axis, |
| |
| B0: 0 = RA left, 1 = RA right. |
| B1 - Bit 8: Always 0 |
| |
| Note: When no keys are pressed Bit 0 is 0 when the controller is set for |
| southern hemisphere operation, and 1 when set for northern hemisphere |
| operation. |
| |
| Word 3: RA speed |
| |
| This word determines the speed of the RA axis in multiples of the |
| sideral rate. There seems to be some logic in the controller for the x2 |
| speed to help with guiding: |
| |
| B3 - 0 Rate |
| 0000 x0 (RA button for opposite direction to hemisphere RA in x2 mode) |
| 0001 x1 (No RA button pressed) |
| 0010 x2 (RA button for same direction to hemisphere RA in x2 mode) |
| 0100 x8 |
| 1000 x16 |
| |
| B8 to B4: All 0 |
| |
| Word 4: DEC sync (?) |
| |
| This word seems to be used to synchronize the start of the DEC |
| information, but it could be used for something else |
| |
| B0 - B7: All 0 |
| B9: Always '1' |
| |
| Word 5: DEC direction |
| |
| This word determines the direction of DEC axis rotation. |
| |
| B0: 0 = DEC UP, 1 = DEC DOWN |
| B1 - B7: All 0 |
| B8: Always 1 |
| |
| Word 6: DEC speed: |
| |
| This word determines the spped of rotation of the DEC axis. |
| |
| B3 - B0 Speed |
| 0000 x0 (no motion) |
| 0010 x2 |
| 0100 x8 |
| 1000 x16 |
| |
| B7 - B4: All 0 |
| B8: Always 1 |
| |
| Notes: |
| |
| - The DEC reverse and RA reverse seem to be inputs to the controller MCU |
| but only control the interpretation of the buttons and are not sent |
| directly to the mount. |
| |
| - see eq6-mnt.txt for pinout of cable |
| |
| Further work: |
| |
| - Need to determine correct "first word" in set by monitoring data from |
| startup |
| - Need to check for any special startup words by monitoring data from |
| startup |
| |