System Alpha Product Design History
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Rev E3 / Sep '25
- Add redundant flyback protection for all switched solenoids
- Further improvement of switch matrix switch-off time
- SOD323 footprint updated for manufacturability

Rev E2 / Jul '25
- Add tank capacitor across game 5V with soft start for compatibility with EzSBC TO-3 switching 5V modules

Rev E / Jul '25
Hardware
- PIC 16F54 MCU replaced with modern Cortex-M0 MCU
- Hardware emulation of original 555 blanking circuit
- Switch matrix sends and returns are now fully 40V tolerant, to protect in case of short to Solenoid V+
- Special Switches are also now fully 40V tolerant, and RC timing adjusted to better match original.

Software
- New Cortex-M0 firmware to perform same Special Solenoid function as well as add Blanking feature
- AVR firmware updated to support new switch matrix logic

Rev D / Jun '25
Hardware
- Misc BOM changes
- 74HC154 replace with 2 pcs 74HC138
- Increase drive strength of switch sends to allow 8 switch rows driving simulataneously
- Updated ribbon cable harness to fix swapped commas on System 7 add-on board

Software
- Add credits = 00 freeplay mode for White Flipper ROM games

Rev C / May '25
Hardware
 - Nothing functional, electrically same as Rev B just silkscreen changes

Software
 - Set White Flipper ROM game DIP switch settings by text file
 - Factory reset any game with presence of settings.txt

Rev B / Apr '25
Hardware
 - Remove DIP switches
 - Separate STM32 and AVR reset lines
 - New power supply scheme:
   - Replace 5V charge pump power supply with Boost converter
   - Source boost converter from 3.3V buck converter
 - Add series resistors to off-board connections
 - Add mounting holes for nylon standoffs
 - Add wire color labels to connectors
 - Change LED colors

Software
 - None

Rev A / Oct '24
 - Initial design