0,0 → 1,125 |
EQ-6/Atlas handpaddle protocol (v3 - 11 Jan 2004). |
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Darren Hutchinson |
dbh@gbdt.com.au |
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$Id: eq6-serial.txt,v 1.3 2004/03/07 07:44:59 dbh Exp $ |
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Introduction: |
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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. |
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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. |
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Cable pinout TBD. |
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Physical format: |
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The signal is a 0/5V signal, with a '1' represented by 5 V. Start bits |
are '0', stop bits are '1' |
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Data format: |
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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. |
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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. |
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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. |
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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. |
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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. |
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Word 1: RA sync |
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This word is always the bit pattern 001111110 (0x07e). |
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B0: Always 0 |
B1 - B6: Always 1 |
B7 - B8: Always 0 |
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Word 2: RA direction |
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This word determines the rotation direction of the RA axis, |
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B0: 0 = RA left, 1 = RA right. |
B1 - Bit 8: Always 0 |
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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. |
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Word 3: RA speed |
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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: |
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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 |
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B8 to B4: All 0 |
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Word 4: DEC sync (?) |
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This word seems to be used to synchronize the start of the DEC |
information, but it could be used for something else |
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B0 - B7: All 0 |
B9: Always '1' |
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Word 5: DEC direction |
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This word determines the direction of DEC axis rotation. |
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B0: 0 = DEC UP, 1 = DEC DOWN |
B1 - B7: All 0 |
B8: Always 1 |
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Word 6: DEC speed: |
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This word determines the spped of rotation of the DEC axis. |
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B3 - B0 Speed |
0000 x0 (no motion) |
0010 x2 |
0100 x8 |
1000 x16 |
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B7 - B4: All 0 |
B8: Always 1 |
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Notes: |
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- 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. |
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- see eq6-mnt.txt for pinout of cable |
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Further work: |
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- 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 |
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