BBC Master GOTEK Interface

Master GOTEK

This is a spin off from the FileStore E01E FDC Board which incorporates a pair of GOTEK circuits.  This is one of those circuits on a small PCB that fits inside the Master connecting to the Internal Floppy Disk interface, connector PL2, a panel fits over one of the Cartridge Slots with the USB socket, OLED Display and a Rotary Encoder.

Please note this board should not be used in conjunction with an external drive, it does not have the required open collector drivers to allow multiple drives.

PL2 is normally not fitted and so needs to have a 34-way double row header soldered in (you may find the holes are filled with solder which needs to be cleared first).

Power is taken from the unused 'Keyboard Con 2' connector, PL7 - a single wire to pin 15 provides +5V to the board, either fit a header to the PCB (PL3) or a flying wire terminated in a single Dupont type socket to plug-in to Master PL7.

The GOTEK will also produce 'floppy drive' sounds which normally go to a small piezo sounder, this signal can be routed to the 'MODEM' interface PL10, connector as follows:

PL10 Pin Signal
1 SPEECH
2 MAN OUT
3 A GND
4 Keyway
5 SND IN

 

 

 

 

Again either fit a header to the PCB( PL4) or a flying wire terminated in a single Dupont type socket to plug-in to Master PL4 pin 5 'SND IN'.

Master GOTEK Fitted

The GOTEK display, rotary encoder and USB socket can be mounted on a 3D printed panel fitted over one of the Cartridge Slots, a suitable panel maybe something like this one designed by John Gray which can be found on Thingiverse, I haven't yet got around to printing and fitting a panel though !

The connections to the Front Panel are via a 10-way ribbon cable connected to PL1, connections as follows:

USB Socket

Pin Signal Connect to PL1 pin
1 +ve 10 (+5V)
2 D- 4 (D-)
3 D+ 5 (D+)
4 -ve 1 (0V)

 

 

 


 

 

OLED Display

Pin Signal Connect to PL1 pin
1 GND 1 (0V)
2 Vcc 9 (+3V3)
3 SCL 2 (SCL)
4 SDA 3 (SDA)

 

 

 

 

 

 

 

Rotary Encoder

Signal Connect to PL1 pin
Switch 6 (SW)
Switch Ground 1 (0V)
Clock 7 (CLK)
Ground 1 (0V)
Direction 9 (DT)

 

 

 

 

The STM32 processor is most easily programmed via its serial port (PL2) using an FTDI USB converter (must be 3V3) and the STM32 Cube Programmer application which can be found here https://www.st.com/en/development-tools/stm32cubeprog.html.  To initiate programming the BOOT0 link (LK1) should be fitted.  If you have an OLED display connected this must be disconnected during programming or the processor will think you are using SPI rather than serial. The GOTEK Flash Floppy firmware can be found here https://github.com/keirf/FlashFloppy/wiki.

Connections to the serial port for programming are as follows:

Schematic

Bill Of Materials

PCB

Master GOTEK PCB

 

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