Receiving deliveries of brand new electronic components is exciting! The order from Mouser included a part for the keyboard controller board and multiple parts for MAXI000. On the same day I also received the previously described PCBs from allpcb.com. Here’s the front of a keyboard controller board: As usual they look great. A quick test of the updated RJ10 socket… Read more »
One critical issue arises when attaching mechanical switches, as found in computer keyboards, to digital electronics: switch bounce. When switches are opened and closed, the connection across the switch contacts does not cleanly transition from its previous state to its new state. Instead the switch contacts will (literally) bounce between the old state and new state before finally, after a… Read more »
My little micro is coming along very nicely. One thing has been lacking for a long time now though: a way to control and use the computer without using the serial console port. In summary a keyboard is required. There are a couple of approaches to interfacing what is essentially a switch matrix with a microprocessor. The two main ones… Read more »
I have, for about a month now on and off, been working on the controller board for the toner-transferring laminator. This involved buying some new tools including a drill press add-on for my Dremel multi-purpose tool, a chuck for the Dremel, and a collection of drill bits in various sizes. First of all, here is a picture of the finished… Read more »
This last month or so I have been working on two fronts: finalising the circuit for the computer, and working on my home made PCB fascilities. So, the circuit is finished. For power the board has two options: USB, like the previous design, and a Molex harddisk power connector. Because of the high current sourcing with a PC power supply… Read more »
It looks like my problems with the counter were down to the 555 timer. Replacing the crufty old 555 with an Atmel ATMega8 generating the clock signal caused the counter to start working properly. Here is the ABEL code: MODULE counter // Defined inputs CLOCK pin 1;RESET pin 2; // Defined outputs Q3..Q0 … Read more »
To learn about I2C I have implemented a serial EEPROM programmer using the same AVR based ATMega8 as my old school paralled programmer. I2C, like SPI, is nice because all signalling between the microcontroller and the memory is along only a handful of wires. This also, at I2C speeds at least, makes it slower but adequate for many applications like… Read more »
The EEPROM programmer is finished! I soldered up the PCB, and after fixing a couple of issues it checks out. My programmer has some very bright LEDs, and to show them off I’ve added a new “debugdelay” option to set how fast the programming should happen. In the process I’ve removed the old “debug” option because the 8KByte flash in… Read more »
This Easter weekend I’ve been working on the EEPROM programmer again. The programmer PCB has been “in production” now for about a week, with a few weeks left. In the meantime I thought I would brush up on my soldering “skills” and make the circuit up on stripboard. This turned out to be a slightly crazy thing to do; stripboard… Read more »
As a little diversion on the bumpy road to the 8bit world of the 6809, I’ve been playing about with some AVR ATTiny’s, specifically the ATTiny85. Mostly to see what they can do and to see if they could be used for interfacing peripherals to an 8bit MPU. These are amazing little beauties; 8Kbyte flash, a tiny amount of RAM,… Read more »