Expander for Siel DK 600
Someone recently contacted me asking if it might be possible to add CC support to the Siel DK600 Expander, so that it could be used without a DK600. I don't have an Expander, but asked him to send me the firmware EPROM so that I could examine it. Also, he sent some photos of the inside of the unit. As some people probably already know, the digital board and the voice board are the same ones used in the DK600. I was not able to find any schematics online for the Expander, but was optimistic that the boards were not modified relative to the DK600. The photos showed some digital board connectors for the front panel installed differently in the Expander, and only one EPROM was used for the code, but otherwise the boards looked the same. Much of the firmware for the Expander is the same as in the DK600. The code that scans the keyboard and the front panel potentiometers was removed. Interestingly, the signals that are used to scan the keyboard in the DK600 are used to read the panel switches in the Expander. The LED display connections and firmware are the same in both units.
Since I had added CC support to the DK600, I already had TMS7000 assembly code to implement that. I was pleased to discover that the Siel Expander 2532 EPROM contained about 500 unused bytes. But then I discovered that the CC code I had written for the DK600 required 800 bytes! So I spent several hours optimizing the code and managed to shrink it down to just 450 bytes. I also added code to save the MIDI channel in battery-backed SRAM, and restore it at power-up. Since the expander hardware is almost identical to the DK600, I was able to test the new CC code somewhat using a DK600. After making the changes and fixing a few bugs, I had 5 bytes free.
The Siel Expander firmware supports setting the MIDI channel. To do this, select preset 96, then hit Enter. The display will show the current value. Now enter a two-digit code (00-15) for MIDI channels 1-16 and hit Enter. I made a small change to this code, so that setting channel 1 (by entering 0) will enable OMNI mode. Setting any other channel disables OMNI mode. The MIDI channel is now saved in RAM which is preserved when power is off. At power-up, the value is read from RAM. If the channel is 1, OMNI mode is enabled. Otherwise, OMNI is disabled, and the saved channel is used.
New Firmware:
A version of the firmware which supports modifying parameters using MIDI CC's is currently being tested.
Here is a scan of the Siel User Manual for the Expander, courtesy of the owner of the above-pictured Expander. (Thanks)
Here is an image of the original Siel 2532 firmware EPROM. I don't know if more than one version was released.
Here is information on the CC numbers supported in the new firmware.
Here is an archive containing a template that someone has generated for the BCR-2000 to work with the new DK 600 (or Expander) firmware that supports CC's. I do not have a BCR-2000, and have not tested this myself.
Please note: Taking an Expander apart and replacing chips must be done carefully, or damage to the synthesizer could result. It should only be attempted by someone familiar with this type of work. I will not be responsible for any damage to any instrument caused by either proper or improper use of the information offered here.