- The XC95xxXL in PLCC44 package are not available any more
- The used Godil is also discontinued
- There's a small mistake in the serial interface
- I want a joystick connection to the keyboard
Many other manufacturers also stopped the production of devices in this housing. So we'll have to increase the difficulty of soldering and start using surface mounted CPLD's.
About the Godil
The new devices lack the pins to the 40p socket. They seem hard to find. So I was thinking if it's possible to use the GODIL50_XC3S500E DIL FPGA module (2 x 50 pin IDC) as a replacement. On the Atom board there will be the 2 x 50 pin male connectors so you can simply plug in the new Godil.
Maybe then we also have some additional I/O for hardware handshaking in the serial device. And if there's more room in this FPGA I could also try to add a simple real time clock with the possibility to generate an interrupt every second, minute or hour.
For the Godil part I need advice and support from Hoglet.
Design fault in the serial interface
If you want to use the 3.3V serial input, it conflicts with Rx (pin 12 of the MAX232) which is also an output. So the MAX232 should be removed for 3.3V serial operations. IMHO two diodes can fix this issue.
There's not a lot of space for an extra connector at the back of the Atom. So I want to replace the 7p DIN socket with a 15p D-type connector which provides joystick, serial and tape I/O.
I will also investigate if the other components are still widely available and components that are (almost) discontinued will also be replaced.
Maybe Robert can also share some ideas about a keyboard. He has constructed a keyboard for his new computer so maybe he can share his experience with us. Hoglet has already a new pcb with the keyboard layout, populated with Beeb key switches.
Please share your thoughts here, but be realistic: there is not much room on the board for many additions like tube ports, user ports etc.