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This is the schematic for the breakaway MBHP_Genesis_LS board included with the MBQG_FP front panel board. This should be sufficient for anyone to build a copy of this circuit on prototype board.


When using the MBHP_Genesis module with a MCU supplied at less than 5V, especially when using several modules in parallel, a buffer circuit will be required between the MCU and the modules. This is a very simple circuit that consists of two 20-pin 74HCT series ICs and two power supply bypass capacitors, and can easily be built on prototyping board.

For buffering the data lines, a bidirectional buffer must be used; a common one is 74HCT245. Connect the eight lines from the MCU board to data pins B; connect the eight lines from the MBHP_Genesis board to data pins A; connect the /OE pin to the buffered /CS line (on the MBHP_Genesis side of the buffer); connect the DIR pin to the buffered /RD line (same thing); and connect a 0.1uF capacitor across the supply rails of the buffer chip.

For buffering the address lines, which are unidirectional from MCU to MBHP_Genesis, use a 74HCT541, with its two /OE pins always active (grounded). Alternatively you can use another 74HCT245, with /OE permanently active (grounded) and DIR set appropriately to always send the signals from the MCU to the MBHP_Genesis board. Again, bypass the supply rails with a capacitor.

Both buffers must be powered from +5V, not +3.3V or whatever the MCU uses. In addition, the MCU must be tolerant of 5V signals being applied to its I/O pins (the CORE_STM32F4 module is tolerant)–otherwise it will damage the MCU!

Parts List

Qty Ref. Deg. Part Name Mouser Part Number Description / Notes
1 U101 74HCT245 595-SN74HCT245N Bidirectional buffer chip
1 U102 74HCT541 595-SN74HCT541N Buffer chip
2 [U101], [U102] 20-pin 0.3“ DIP socket 571-1-2199298-6 Socket for chips
2 J101, J102 10×2 pin header, 0.1” pitch 649-68691-420HLF Connectors to core and MBHP_Genesis module
1 J103 2×1 pin header, 0.1“ pitch 571-826936-2 Connector for +5V power from core
2 C101, C102 0.1 uF 21RZ310-RC Power supply filtering capacitors for chips (place one next to each chip's +5V connection)
1 C103 10 uF 140-REA100M1HBK0511P Power supply filtering capacitor for board
1 e.g. 854-SB4 Prototyping board to build circuit on
mbhp_genesis_ls.txt · Last modified: 2016/11/22 19:22 by sauraen