New firmware for Crumar bit 01, bit 99 (AKA Unique DBK), and bit One Synthesizers
The bit 01 was first:
Several people recently asked if I could add CC's to the Crumar bit 01. As I had spent some time a few years ago looking at the bit 99 code, I decided to look into the bit 01 firmware to see how similar it was. As it turns out, it is very similar, so I had a big head start with everything I had learned about the bit 99. Most of the variables are in the same locations. I set up a simulation of the bit 01 so I could refresh my memory and go much deeper into its inner workings.
I was able to line up several people to test the new firmware, so I now have a version of the bit 01 firmware which supports editing parameters using MIDI CC's and also saving all patches using MIDI sysex. My new firmware used the C2/D EPROMS as the starting point.
Here is a document showing the assignment of CC's to parameters for the new bit 01 firmware.
Saving patches via MIDI sysex:
One useful addtion to 80's synths that do not have it is a way to save patches using MIDI sysex. This is easier to use and more reliable than tape backups. The bit 01 has no MIDI out jack, but it does have MIDI thru, so I devised a way to modify this jack to support MIDI out for saving the patches. I re-purposed the tape output signal for MIDI out patch save. This meant that it was only necessary to modify the rear panel jack pcb, and not the main logic board. Here are instructions for modifying bit 01 MIDI Thru to support sysex patch saving. Note: This modification is only necessary for saving patches via sysex. It is not required in order to use MIDI CC's. You will only be able to save patches as sysex with the new firmware installed.
Then the bit 99/Unique DBK:
Once the new firmware was working, someone asked if I could make the same changes to the bit 99, so I worked on that for a few weeks, and found some people to test that one as well.
Here is a document showing the assignment of CC's to parameters for the new bit 99 firmware.
And finally, the bit One:
And, of course, with those two done, someone suggested I make the same changes to the bit One, so I worked on that for a few weeks and lined up some people to test that one too. I modified the bit One jacks pc board to change MIDI Thru to a second MIDI out port, only used to dump patches with the new firmware. (MIDI Out on the bit One is driven by the key MCU, and only contains Note On/Off messages. The main CPU has no access to this port) I used the tape output signal for this, so Tape Out is no longer supported, but Tape In was not affected. Here are instructions for modifying bit One MIDI Thru to support sysex patch saving. Note: This modification is only necessary for saving patches via sysex. It is not required in order to use MIDI CC's. You will only be able to save patches as sysex with the new firmware installed.
My firmware was based on the A3/B2 EPROMS. It seems that EPROMs labeled B2 and B3 contain the same exact data.
Although my firmware was based on code taken from a bit One with CEM filter chips, it has also been tested in two units with SSM filter chips, and seemed to work properly in those as well. The CPU boards are the same in both versions. The voice board was changed, but seems to have the same address mapping for the different control voltages. There are many differences between the different revisions of the bit One firmware, but so far I have not found anything that is related to the different filter chips, so perhaps the differences were handled purely in the hardware design.
Here is a document showing the assignment of CC's to parameters for the new bit One firmware.
I also changed all three versions to not select MIDI OMNI mode at power up, and to not select MIDI channel 1 either, so the previously selected MIDI channel(s) should remain.
Better information on adjusting the trimmers:
I have created three new documents with suggestions for adjusting the trim pots on the Bits. One is for the Bit 01, one is for the Bit 99, and one is for the Bit One. These should be improvements over the information that was here.
Debugging a bit 99 with no sound:
Recently I was given a Crumar bit 99, in the guise of a Unique DBK. The display changed when I selected different patches, but there was no sound when I pressed keys. A web search turned up several related schematics: Crumar bit One and also Crumar bit 01, which seems to be closer. Neither of these is an exact match for the bit 99, but the circuits are very similar, and those schematics are a lot better than none at all. I looked at the DAC output, and the analog signals feeding into the output board, but none of the signals changed at all when I pressed keys.
The bit 99 uses an 8031 (a romless 8051) plus external EPROM and RAM for the main control CPU. It also has an 8051 mounted on the underside of the keybed, for keyboard scanning and velocity measurement. There are two cables connecting the keyboard to the rest of the unit. One has just four wires and connects to the power supply board. This one is called JO. I think the pinout is:
Left pin - 5V
Other three pins - Ground
The other cable has six wires, and connects to the front panel pcb, at a location called JN. I think the pinout of this one is:
1) 59 KHz clock. I think this is being fed to the keyboard.
2) Floating? seems to have a triangle wave on it, maybe just noise from the next signal over?
4) Seems to be Ground
5) Keyboard serial data stream. Std async serial data (lsb first), two bytes, sent only when a key is pressed, or released. Baud rate appears to be 31.25 KHz (the MIDI baud rate). Looks like first byte is the key number, starting at 18h (24 dec) with the lowest key, and incrementing from there. The second byte varies, so it's probably related to velocity on key press. On key release, the second byte is 00h, which makes sense.
6) 2.0 MHz clock. Not sure where this comes from.
In my unit, none of the signals on this connector changed when I pressed keys, so I figured there must be a problem with the keyboard itself. Turns out one of the traces from the 8051 to its 12 MHz crystal was eaten away, so there was no clock to the keyboard scan MCU. A few other traces also looked a little "iffy" so I fixed all of them by adding wires to jumper the marginal areas. I re-assembled the keyboard and the unit started to make noise. I downloaded the first ten patches using MIDI and my PC and started playing chords, and selecting different programs. Anyway, all six voices are working, and I am now up to 40 programs downloaded. I guess the 8031 wasn't fast enough to keep up with downloading the entire set at once.
Crumar bit 99 Firmware EPROM Images:
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