BOSS DR55 RAM replacement / midi kit -project

This project is oldie, bit forgotten, but it deserves a comeback. It’s a Arduino / Atmel ATMega328 based midi upgrade for DR55 replaces the TC5501 SRAM. It acts like the original RAM but it can also carry out extra tasks such as midi receiving and transmitting. Without midi connectors fitted, the operation of the DR55 remains the same as on stock DR55, so it’s possible to use this as replacement of 9V battery killed RAM.

New features so far are:

  • Midi clock sync: Internal clock is rejected if the midi clock is received. Midi clock pulse triggers hihat as in original one.
  • Patterns 7 and 8 (12 steps) has different prescale for midi clock keeping the bar tempo same as 4/4 patterns
  • It responses the midi in notes. Accent is enabled if velocity is greater than 100.
  • On internal playback mode the sequencer output is echoed to midi out.
  • Amount of patterns stored in memory is doubled. Active bank is selected during the power up, by setting variation switch position (A or B).
  • All patterns and settings are stored in eeprom in the controller. Batteries aren’t needed for maintaining the contents of the memory.
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Memory expansion for P5 rev2

Here’s another project I’ve been figuring for some time turning something real. One of the limitations of the rev2 has been small 128 byte memory which has is more or less totally used specially with the upgraded firmware.

Here’s a 2k expansion board which replaces the 60B10 memory on board. The SPRAM is now expanded to 1k and second 1k is used for patch memory upgrade.

The bank select runs from 00 to 98, 51-98 can be selected between expanded memory or factory patches.

Expansion sits piggybacked on rom2 socket and two pins are inserted where the removed 68B10 was. Extra wires carry battery supply and /ce -signal.