SSC-32 General Purpose Sequencer

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SSC-32 General Purpose Sequencer.

Author: Mike Dvorsky

Version: 1.00

Date: Jan 15 2008

Table of Contents

<li><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#eeweer">EEW, EER commands - EEPROM Write, Read</a>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#eewform">EEW Format</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#eerform">EER Format</a>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#seqform">Sequence Format</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#eerhead">Header</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#srvspdl">Servo/Speed List</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#timepwl">Time/Pulse Width List</a></li>

</ul>

</li>

</ul>

</li>

<li><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#memmap">Memory Map - Sequences in External EEPROM</a>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#loc01">Location 0-255: Sequencer Pointer Table</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#loc02">Locations 256-32767: Sequence Data</a></li>

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</ul>

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</li>

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<li><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#gennotes">General Notes on Programming EEPROM</a></li>

</ul>

</td>

<li><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#seqex">Sequence Example</a>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#seqpoint">Sequence Pointer Table</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#seqhead">Sequence Header</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#srvspeed">Servo/Speed List</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#timepw">Time/Pulse Width List</a></li>

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</ul>

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</li>

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<li><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#seqcom">Sequencer Commands</a>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#playstart">Start a player</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#playstop">Stop a player</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#playspd">Change the speed of a player</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#playpau">Change the pause value of a player</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#gotostep">Go to a step in a sequence</a></li>

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<li class="toc"><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#playque">Query a player</a></li>

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</ul>

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</li>

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<li><a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-system/ses-electronics/ses-modules/ssc-32/ssc-32-general-purpose-sequencer/#seqcomex">Examples of Sequencer Commands</a></li>

</ul>

</td>

</tr>

</tbody></table>

<a name="eeweer">EEW, EER commands - EEPROM Write, Read.</a>

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The EEW and EER commands are used to write and read external EEPROM data. In order for these commands to be used, an EEPROM chip must be

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installed in the 8-pin socket on the SSC-32. The chip used for testing is a Microchip 24LC256-I/P which has 32768 bytes of storage. Other I2C

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serial EEPROMs with comparable pinout should work, but have not been tested.

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The primary use of external EEPROM is to store sequences for the General Purpose sequencer. The first 256 bytes of external EEPROM are reserved

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exclusively for the GP sequencer, but the other bytes may be used for other purposes.

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EEPROM read and write commands are issued with arguments in decimal format, but the response to an EEPROM read command is in binary format. This

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is in keeping with the SSC-32 convention of receiving commands in decimal format and providing responses in binary format.

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NOTE: The current firmware version (SSC32-V2.01GP) requires a '-' character before the address in EEPROM read and write commands. If this

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character is omitted, the EEPROM access will be performed on internal EEPROM of the ATMega168 processor. Future firmware versions will not require

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the '-' character for external EEPROM access.

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NOTE: No external EEPROM read or write accesses should be performed while a sequence is executing out of external EEPROM.

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<a name="eewform">EEW Instruction Format</a>

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EEW -<addr>,<byte>,<byte>,<byte>,...,<byte><cr>

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<ul>

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<li><addr> = the starting address of the data to be written, in decimal format</li>

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<li><byte> = a byte of data to be written to external EEPROM, in decimal format</li>

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</ul>

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The EEW command writes up to 32 bytes of EEPROM. To write more than 32 bytes, issue multiple commands. The command may take several milliseconds

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to complete. When performing multiple successive EEW commands, it is recommended that you wait for each command to complete before starting the next

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command. There are several ways to do this:

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<ul>

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<li>Delay 10ms between EEW commands.</li>

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<li>Use an EER command to read back the data just written. The EER command will not return until the EEW has finished.</li>

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<li>Issue any command that receives a response from the SSC-32. The SSC-32 will not respond to any commands until the EEW command has finished.</li>

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</ul>

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Example: write 8 bytes of external EEPROM starting at address 256. Write the values 12, 34, 56, 78, 90, 98, 76, 54.

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EEW -256, 12, 34, 56, 78, 90, 98, 76, 54<cr>

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NOTE: The EEW command will complete faster if the starting address is a multiple of 32. If you have a large block of data to write, begin by

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writing any unaligned portion; then write 32-byte aligned blocks; finally write any remaining unaligned portion.

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<a name="eerform">EER Instruction Format</a>

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EER <addr> ; <nbytes>

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<ul>

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<li><addr> = the starting address of the data to be written, in decimal format</li>

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<li><nBytes> = the number of bytes to read, in decimal format</li>

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</ul>

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The EER command reads up to 32 bytes of EEPROM. To read more than 32 bytes, issue multiple commands. The return value from the EER command is a

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string of bytes, in binary format.

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Example: read 8 bytes of external EEPROM starting at address 256. (Assume the values in EEPROM are the values programmed in the previous

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example.)

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EER -256;8<cr>

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result: 12 34 56 78 90 98 76 54 (binary)

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<a name="memmap">Memory Map - Sequences in External EEPROM</a>

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Sequences stored in external EEPROM must follow a defined format, as described below. The first 256 bytes are reserved for the Sequence Pointer

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Table, but the remaining bytes may be used for other purposes, as long as they are not part of a sequence pointed to by an entry in the Sequence

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Pointer Table.

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<a name="loc01">Locations 0 - 255: Sequence Pointer Table</a>

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The Sequence Pointer Table contains the addresses of the sequence starting locations in EEPROM. Valid starting addresses are 256 - 32767. If

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there is no sequence for a particular sequence number, the Sequence Pointer Table entry should be 0 or 65535. The addresses are stored in big-endian

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format, with the high byte in the lower address.

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@0:1 = pointer to sequence 0 (high byte in address 0, low byte in address 1)

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@2:3 = pointer to sequence 1

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@4:5 = pointer to sequence 2

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@6:7 = pointer to sequence 3

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Etc., up to sequence 127

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<a name="loc02">Locations 256 - 32767: Sequence Data</a>

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The sequence pointer table entries point to sequence data. Sequences may be stored at any location, but the only way a sequence can be accessed

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is through the Sequence Pointer Table.

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<a name="seqform">Sequence format</a>

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Each sequence has 3 contiguous sections

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<ul>

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<li>Header - containing the sequence number, number of servos, and number of steps</li>

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<li>Servo/speed list - containing a list of all the servos and the maximum move speed for each servo</li>

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<li>Time/pulse width list - containing the move time and pulse widths for each step</li>

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</ul>

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<a name="eerhead">Header</a>

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The header consists of 3 bytes

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<ul>

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<li>Sequence number</li>

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<li>Number of servos</li>

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<li>Number of steps</li>

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</ul>

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The sequence number must match the sequence number of the Sequence Pointer Table entry. The number of servos may be from 1 to 32. The number of

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steps may be from 1 to 255.

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<a name="srvspdl">Servo/Speed List</a>

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The servo/speed list consists of 3 bytes per servo. The size of the servo/speed list must match the number of servos in the header.

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<ul>

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<li>Servo number for 1st servo</li>

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<li>Speed high byte for 1st servo</li>

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<li>Speed low byte for 1st servo</li>

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<li>Servo number for 2nd servo</li>

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<li>Speed high byte for 2nd servo</li>

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<li>Speed low byte for 2nd servo</li>

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</ul>

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The servo numbers must be 0-31. Speeds are 0-65535 us/second just like move commands.

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<a name="timepwl">Time/Pulse Width List</a>

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The Time/Pulse Width List specifies the servo positions (a.k.a. pulse widths) for each step in the sequence, and the amount of time to move from

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step to step. The list alternates between servo pulse widths and move times. It begins and ends with a move time.

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<ul>

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<li>Step 0 PW, PW,..., PW (one PW for each servo)</li>

</ul>

If there are M servos and N steps in a sequence, the time/pulse width list consists of 2*(M+1)*N + 2 bytes.

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There are several things to note about the time/pulse width list:

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<ol>

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<li>The Step (N-1) -> 0 move time is duplicated, appearing at the beginning and the end of the list. This makes it easier for the SSC-32 to play

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sequences in reverse.</li>

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<li>Move times are in ms, just like move commands.</li>

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<li>Move times are 2 bytes each, with the high byte appearing first (i.e. big-endian).</li>

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<li>The move times should be the times for a normal move speed. The speed can be adjusted faster or slower as the sequence is played. The range of

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adjustment is from 0 to 200% of the programmed speed, either forward or reverse.</li>

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<li>Pulse widths are in us, just like move commands.</li>

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<li>Pulse widths are 2 bytes each, big-endian.</li>

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<li>The pulse width entries for each step must exactly match the list of servo numbers in the servo/speed list.</li>

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</ol>

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<a name="gennotes">General notes on programming EEPROM.</a>

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<ul>

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<li>Write no more than 32 bytes at a time. For the fastest write speed with external EEPROM, make as many writes as possible start on a 32-byte

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boundary. For example, to write a 1000-byte block starting at address 500, begin by writing bytes 500-511 in a single 12-byte write. Then do 30

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writes of 32 bytes each--these writes will all start on 32-byte boundaries. Finally, write the last 28 bytes in a single write.</li>

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<li>After writing sequences to external EEPROM, it is recommended that you verify the contents of external EEPROM by reading back the bytes

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written.</li>

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<li>Bytes of external EEPROM can be used for other purposes than storing sequences, as long as no Sequence Pointer Table entries point to these

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bytes. For example, a portion of EEPROM could be reserved for storage of text strings describing the sequences. This way, when the sequences are

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read out of EEPROM, there will be some clue to what the sequence is intended to do.</li>

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</ul>

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<a name="seqex">Sequence Examples</a>

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Here is a simple example of a sequence. The sequence will move 2 servos through 3 steps. The servos will be servo #9 and servo #10. The steps

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will be:

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Step 0: Servo #9 = 1500us, servo #10 = 1500us

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Step 1: Servo #9 = 1000us, servo #10 = 1500us

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Step 2: Servo #9 = 1000us, servo #10 = 2000us

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Moving from step 0 to step 1 will take 600ms, from step 1 to step 2 will take 1200ms, and from step 2 to step 0 will take 2400ms.

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The sequence number will be 5, and it will be stored beginning at EEPROM address 500.

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<a name="seqpoint">Sequence Pointer Table</a>

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First, the Sequence Pointer Table must be set so that sequence 5 begins at address 500. Sequence 5 begins at EEPROM address 10. When the number

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500 is split into 2 bytes, the high order byte is 1 and the low order byte is 244 (500 = 1*256 + 244), so the Sequence Pointer Table value starting

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at address 10 will be

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@10 = 1

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@11 = 244

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The EEW command to write this portion of the Sequence Pointer table is

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EEW -10, 1, 244

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<a name="seqhead">Sequence Header</a>

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The sequence header is 3 bytes that specify the sequence number (5), number of servos (2), and number of steps (3). The sequence header begins at

EEPROM address 500:

@500 = 5

@501 = 2

@502 = 3

The EEW command to write the sequence header is

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EEW -500, 5, 2, 3

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<a name="srvspeed">Servo/Speed List</a>

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The servo/speed list has 3 bytes per servo (1 byte servo number, 2 bytes maximum speed). For this sequence, the maximum speeds will be 65535 =

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255*256 + 255. The servo/speed list begins immediately after the sequence header, at address 503:

@503 = 9

@504 = 255

@505 = 255

@506 = 10

@507 = 255

@508 = 255

The EEW command to write the sequence header is

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EEW -503, 9, 255, 255, 10, 255, 255

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<a name="timepw">Time/Pulse Width List</a>

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The time/pulse width list has the servo pulse widths for each step, and the times to move between the steps. The servo pulse widths in this

example are

<ul>

</ul>

The move times in this example are

<ul>

</ul>

The time/pulse width list begins immediately after the servo/speed list, at address 509:

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@509 = 9 Step 2 to step 0 time = 2400

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@510 = 96

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@511 = 5 Step 0, servo 9 = 1500

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@512 = 220

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@513 = 5 Step 0, servo 10 = 1500

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@514 = 220

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@515 = 2 Step 0 to step 1 time = 600

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@516 = 88

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@517 = 3 Step 1, servo 9 = 1000

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@518 = 232

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@519 = 5 Step 1, servo 10 = 1500

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@520 = 220

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@521 = 4 Step 1 to step 2 time = 120

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@522 = 176

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@523 = 3 Step 2, servo 9 = 1000

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@524 = 232

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@525 = 7 Step 2, servo 10 = 2000

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@526 = 208

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@527 = 9 Step 2 to step 0 time = 2400

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@528 = 96

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The EEW command to write the time/pulse width list is

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EEW -509, 9,96,5,220,5,220,2,88,3,232,5,220,4,176,3,232,7,208,9,96

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<a name="seqcom">Sequencer Commands</a>

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These are the commands that allow you to play programmed sequences. The SSC-32 has two "players" that can each play a sequence. The players

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may be used simultaneously, and other servo move commands may be sent to the SSC-32 while players are playing.

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NOTE: Do not simultaneously play two sequences that use some of the same servos. The results will be unpredictable.

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NOTE: Do not issue servo move commands that use servos in a playing sequence. The results will be unpredictable.

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<a name="playstart">Start a player</a>

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The following command starts a player playing a specified sequence, with several parameters.

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(The notation <x> indicates a number that is one of the parameters to the command. The notation "[xxx]" indicates an optional part of

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the command.)

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PL SQ <s> [SM <m>] [IX ] [PA <pa>] [ONCE]

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<ul>

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<li>PL Specifies player p, either 0 or 1</li>

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<li>SQ <s> Specifies sequence number s, from 0 to 127</li>

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<li>SM <m> Specifies speed multiplier m, from -200 to 200</li>

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<li>IX Specifies starting index i (a.k.a. step number), from 0 to 255</li>

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<li>PA <a> Specifies pause between steps, a, in milliseconds from 0 to 65535</li>

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<li>ONCE Specifies that the sequence is played only one time</li>

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</ul>

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The SM value is a percentage of the speed based on the move times in the programmed sequence. The larger the number the faster the sequence

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plays, up to 2 times the speed of the programmed sequence (for a speed multiplier of 200%). If the SM value is negative, the sequence is played in

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reverse. The SM value does NOT affect the maximum speeds for the servos. If SM is not specified, it defaults to 100%.

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The IX value specifies which step should be first when the sequence is started. The player will attempt to move the servos gradually to the

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starting position. If IX is not specified, it defaults to 0.

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The PA value specifies the length of a pause that is inserted between steps in the sequence. The value is in milliseconds. If PA is not

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specified, it defaults to 0.

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The ONCE option specifies that the sequence is played only one time, and then the player stops. The servos will start and end at the position

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specified by the IX parameter (or 0 if IX is not specified). If ONCE is not specified, the sequence will repeat continuously until the player is

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stopped by a user command.

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<a name="playstop">Stop a player</a>

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The following command stops a player immediately.

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PL

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<a name="playspd">Change the speed of a player</a>

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The following command changes the speed of a player. The player must already be playing a sequence for this command to be valid.

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It is possible to set the speed to 0. In this case, the servos will stop moving but the sequence will still be playing and can be restarted by

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changing the speed to a non-zero value.

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PL SM <m>

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<a name="playpau">Change the pause value of a player</a>

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The following command changes the pause value of a player. The player must already be playing a sequence for this command to be valid.

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PL PA <pa>

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<a name="gotostep">Go to a step in a sequence</a>

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The following command causes a group of servos to move to one of the steps in a sequence. The step number and move time can be optionally

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specified. This command is equivalent to a normal group move command, except that the servos and maximum speeds are obtained from the specified

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sequence. The T parameter in this command works exactly like the T parameter in a normal group move command.

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NOTE: This command is independent of any player, and may be issued even if both players are playing sequences. Like any servo move command, this

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command should not be used if it will cause servos to move that are part of a currently playing sequence. The results will be unpredictable.

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SQ [IX ] [T <t>]

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<a name="playque">Query a player</a>

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The following command causes the SSC-32 to return information about the state of a player.

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QPL

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The QPL command returns 4 bytes of binary information:

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<ol>

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<li>The sequence number being played (or 255 if no sequence is being played)</li>

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<li>The index moving from in the sequence (0 through the maximum step number)</li>

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<li>The index moving to in the sequence</li>

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<li>The remaining time in the step, 100ms per bit (e.g. if there are 700ms remaining, the value will be 7)</li>

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</ol>

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<a name="seqcomex">Examples of Sequencer Commands</a>

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Start player 0 playing sequence 5. Start at step 0, 100% forward speed, no pause between steps, play continuously.

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PL 0 SQ 5

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Change the speed of player 0 to 50% reverse speed.

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PL 0 SM -50

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Pause player 0 (set the speed to 0)

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PL 0 SM 0

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Change the speed of player 0 to 200% forward speed.

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PL 0 SM 200

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Change the pause between steps for player 0 to 1000ms (1 second).

PL 0 PA 1000

Stop player 0.

PL 0

Go to step 3 of sequence 20.

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SQ 20 IX 3

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Go to step 5 of sequence 20, taking 2000ms (2 seconds).

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SQ 20 IX 5 T 2000

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Start player 1 playing sequence 15. Start at step 2, 70% reverse speed, play one time only.

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PL 1 SQ 15 IX 2 SM -70 ONCE

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</div>

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</body>

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Wiki source code of SSC-32 General Purpose Sequencer

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