Category: Hardware

lzoDSO – hardware prototype

Posted by lazlo – April 11, 2013

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lzoDSO hardware prototype

Recently I have been working on my oscilloscope project. Documenting ideas, digging out requirements and restructuring the whole projects documentation wiki. While doing so I realized that the page was totally confusing to new visitors since it does not say that there is no finished scope yet (even though there is a picture of one). What one can see on the pictures is actually a prototype. Until now we did not explicitly say so. This is NOT the final thing.

To address that issue we added a Status section to the start page of the wiki that clarifies the projects state.

Now the interesting part: We created a new page for the prototype which is linked on the wikis start page and moved existing files related to the components of the prototype from /trunk to /branches/prototype-a.

Next step will be to take the legacy firmware we have and adjusted it to make it run on the prototype hardware. When the firmware is ported (basically adjust pin mappings, enable/disable functionality) we will use is as the starting point to get the code incrementally refactored until we replaced everything with test-driven code.

Hand Soldering Techniques – Surface Mount

Posted by lazlo – April 3, 2013

lzoDSO – a DIY Oscilloscope

Posted by lazlo – March 19, 2013

After quiet a while I have started to put my oscilloscope project online. Work is still in progress but I decided it won’t hurt to have online what has been done so far.

PPD file for Lexmark E330

Posted by lazlo – September 27, 2011

During last week my new (refurbished) Lexmark E330 monochrome laser printer arrived (for 20€!!! – got it from some reseller at amazon). Before I chose the printer I took care of making sure it supports PCL (of which I thought will raise the chances of having proper support for CUPS and hence Linux). After printing a first test page with the “Generic PCL Laser Printer” driver I started looking for a “real” E330 PCL driver (no, CUPS does not come with a PPD for the E330). So I checked the Lexmark page and was surprised they also had other drivers than for Windows. Anyway I downloaded the Windows driver (since I was looking for the PPD which is usually included in some way or another in those setup.exe files those companies usually supply in order to set up their printers under Windows). I think I downloaded like five or more files but they where not very helpful. Day later, almost sure to be stuck with the default PCL driver I had another look at the CUPS page where I downloaded a PPD file for a E323 (which is supported) only to figure out if it might give me some clue for what strings to search for in order to find the correct file. I ended up looking for “PPD File for Lexmark E330” … and found exactly 1 match – this page. Looks just like a PPD file for the E330. Took me a run of “copy&past into new file, add new printer, select PPD file, print test page” to be very happy with my new laser. Now the test page looks just as you would expect it to be.

external memory board

Posted by lazlo – September 24, 2011

Just before writing my last post, I started building another board in order to supply my ATmega128 with 64Kbytes of external memory (in fact the so called “XMEM” feature was one of the reasons I bought that chip).

The board is designed for a 28 pin S-RAM IC (Hitachi HM6264) that can be connected to a micro controller supporting external memory (like the ATmega128 or ATmega162) using three 10 pin headers. The first header is used for the multiplexed lower address/IO bits (port A on micro controller), the second for dedicated upper address bits (port C) and the last for read/write strobe and address latch enable (port G). All headers share two common last pins: GND (9) and VCC (10). The only thing required except for the S-RAM itself, some pin headers and a 100uF ceramic capacitor is a octal latch IC (74AHC573) that will allow for multiplexing the shared lower address/IO lines.

NOTE

After looking up the “Address Latch Requirements” section in the ATmega128 datasheet turns out that when the micro controller is operated above 8MHz (mine has a 16MHz crystal) the 74HC573 (the IC I have) does not meet requirements but a 74AHC573 would do. I guess I will put in a 8MHz crystal until I can get hold of a 74AHC573.

 

 

 

 

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base board for Olimex ATmega128 header board

Posted by lazlo – September 23, 2011

A couple of months ago I ordered a ATmega128 header board (AVR-H128) from Olimex. In order to make use of such a header board you need to mount it somewhere. For this purpose I created a sort of header board for the header board. It is very minimal, consisting of mechanical components only except for a LED and a resistor. The reason for that is that the header board on which the ATmega128 itself is placed already contains a +5V voltage regulator (LM78L05) and reset circuit (ZM33064). Using my board its very convenient connecting things to the pins of the micro controller. All ports (A, B, C, D, E, F and G) have a separate 10 (2×5) pin header where the last two pins of each header is connected to GND (9) and VCC (10).

The layout of the board was created with the intention in mind to be able to assemble it in a through-hole fashion. Needless to say that the layout can also be used to etch or mill the board.

There are still things that can be enhanced like adding a connector for the reference voltage of the ADC (AREF).

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Schematics and layout have been created using Eagle 5.11 with a non-commercial license. The outline of the board is 100x160mm, so for you folks that use the Eagle freeware you will not be able to modify the boards layout (since Eagle as freeware only allows for boards with a outline of 100x80mm).