The "MAXIMITE" computer
Page last updated on August 16, 2011
In the March edition of the Australian magazine, "Silicon Chip" there is an article on building a very simple single board computer, by Geoff Graham. See here for full details.
There is a discussion group for Maximite "www.thebackshed.com"
This sparked my interest as it lead me back to the 1980's when I built the DSE computer project and others.
Being impatient, I decided to make my own PCB, rather than wait for the kit to be released in April or May. The PCB is tricky to make, as the original used a plated through PCB. So, I changed the layout a little, to make all of the through holes accessible. (some were under the PIC device on Geoff's version) The resistors were changed to SMD parts also.
I ordered the PIC32 device from the USA and you can see my progress, below.
click for larger size picture.
Here are some files for the home made pcb. It is a pdf that you can print to a transparency for the usual type of home made pcb making. NOTE ! files are presented 'as-is' with no guarantees. Some pads are smallish and you will need a good eye and steady hand to drill the holes, or a good vertical drill press. The SD card holder I used is not the one specified in the original articles. It is hard to get. I used another compatible type bought from www.jaycar.com.au Details are in the schematics in above files.
The PIC32 chip arrived. Fitted it up and after a couple of small errors due to soldering, it all works !
I used a 1GB SD card loaded with Geoff's sample BASIC programs to test it out. (card not shown)
I have a later version of firmware, released late March 2011 which adds an extra command.
I am very impressed with the quality of the screen display. I have the PCB setup for both VGA and composite displays and used an old VGA monitor and keyboard. Still need to test the USB interface.
I understand I may be the 1st to have a MAXIMITE up and running outside of Geoff's beta testers.
Probably the only home brew PCB too. I plan to also make a small interface board to plug into the 26pin connector, for interfacing to various signals.
It would also be handy if the MMBasic had provision for IIC commands. There are many cheap IIC devices around these days and I would like to use some of these devices if possible. Chips like real time clocks (battery backed) temperature and humidity sensors and the like. Maybe build a "weather station" that can log data to the SD card. This would be a neat project but needs a reliable clock for long term use.
UPDATE: Aug, 2011 ..... there is now full support for IIC commands in the latest code release! Ref, the discussion group above.
I have a 5" colour TFT display that uses IIC commands which would be nice to use if the IIC code becomes available some time. This screen supports line drawing, boxes, fill and text.
Info on the TFT interface PCB here http://www.carnut.info/tftpcb/tft.htm
This is a TFT display ex a Sony PSP1000. These screens are available as replacements and are quite cheap. About $25 or so on eBay. The PCB above it, is a driver board for the TFT which is driven using IIC based commands.
A 5" screen with touch screen can also be fitted to this TFTA pcb. 5" screens are about $45 on eBay.
Above is the picture using the A/V output, into a little TV set I have. I placed my finger on the Analog input of the MAXIMITE andthat is 50Hz hum displayed on the screen.
This project is a credit to Geoff's ingenuity. Geoff's web pages are excellent with descriptions of all aspects of the project.
I am sure this project will be a big hit with Silicon Chip readers!
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Page created by vk3pe on 28th Feb, 2011.