Amiga 1200 keyboard MPU drop-in replacement pcb
As the 68HC05 (p/n 391508-01) used in the Amiga 1200 is getting to be very expensive, I designed a drop-in replacement pcb using Atmel (Microchip) MPU - ATMEGA324PB-20MU.
Advantages:
- No crystal required
- No Voltage monitor IC required
- SW can be updated to support an external keyboard with other protocol. Connected e.g. to the unsoldered crystal's pins.
How it looks:
Designed with "IAR EW for Microchip AVR 7.30".
To download the hex code an STK500 can be used with avrdude tool. A batch file for avrdude is included in "firmware\release\exe" folder as well as in "\debug\exe").
STK500 to the pcb connection is shown below:
To fit the MPU's footprint it shall be made with "castellated holes" technology, which is expensive. So I made a simple board with normal holes. This board needs to be cutted to fit the footprint as shown below.
Both gerber files included in the "PCB" folder:
- A1200_keyb_mpu_olm_normal_Gerber.zip - Normal pcb, to be trimmed.
- A1200_keyb_mpu_olm_cast_holes_Gerber.zip - Ready to be produced with "castellated holes" technology.
Passive components are 0402(imperial) size.
The pcb is not compatible with a PLCC socket. Must be soldered to Amiga's pcb.