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kaklik |
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EQ-6/Atlas handpaddle protocol (v3 - 11 Jan 2004).
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Darren Hutchinson
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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
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Atlas/EQ-6 mount. The hand controller also acts as a power switch for
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the mount.
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The communication bewteen the controller and the mount is
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unidirectional, with data being sent from the controller to the mount
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over a single wire. The other wires provide ground, +12V from the mount
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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
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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,
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9 data bits, and 1 stop bit. The bits are transmitted at rate of 935
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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
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the first in the set of words. The ordering below is a guess based on
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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
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which keys are pressed but it seems unlikely that this is detected or
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used by the mount.
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The six words are divided into two sets of three, one set for RA, the
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other for DEC. Each set contains a sync word, a direction word, and a
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speed word.
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All words below are shown with the most significant bit on the left. The
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least significant bit is transmitted first, immediately after the start
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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
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B1 - B6: Always 1
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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.
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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
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southern hemisphere operation, and 1 when set for northern hemisphere
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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
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sideral rate. There seems to be some logic in the controller for the x2
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speed to help with guiding:
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B3 - 0 Rate
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0000 x0 (RA button for opposite direction to hemisphere RA in x2 mode)
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0001 x1 (No RA button pressed)
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0010 x2 (RA button for same direction to hemisphere RA in x2 mode)
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0100 x8
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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
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information, but it could be used for something else
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B0 - B7: All 0
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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
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B1 - B7: All 0
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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
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0000 x0 (no motion)
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0010 x2
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0100 x8
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1000 x16
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B7 - B4: All 0
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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
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but only control the interpretation of the buttons and are not sent
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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
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startup
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- Need to check for any special startup words by monitoring data from
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startup
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