VS Electronics and Embedded Development

Development Wiki

vsergeev — Mon, 03 Dec 2007 23:55:54 +0000

While wordpress is nice as a blog, it feels like a crude content management system for electronics projects that might have many images (pictures, schematics) and extra files (code, schematics). Also, I never liked the size wordpress scaled uploaded images to, or where it stored the images (although there might be a third party plugin or modification to better customize this process), so I’ve always been reluctant to upload images and then manually scale them to my preferred size with “convert.”

Recently I’ve launched a development wiki powered by DokuWiki. It’s not really a wiki, since I’m the only one that can edit it, but I think it will work as a good backend for my project site. You can find the development wiki here: http://dev.frozeneskimo.com/.

I’ve already moved most of the projects from my blog to my wiki, and even added a new one (the Parallel SRAM one). This blog isn’t going anywhere, I think it’s great for news/project updates and the like, but the actual project content will be stored on the wiki.

Interfacing with Parallel SRAM

vsergeev — Mon, 03 Dec 2007 23:43:39 +0000

A typical parallel SRAM chip has always been on my list of things-to-interface-with so I decided to take up this mini-project a little while ago. It’s pretty straightforward. I’ve put the explanation, schematic, and source code for interfacing an ATMega32 to a 32 kilobyte SRAM chip, you can find it here: http://dev.frozeneskimo.com/embedded_projects:parallel_sram.

And here’s a picture (can’t forget it):
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deja-packet version 1.0 released

vsergeev — Sat, 30 Jun 2007 20:48:45 +0000

This is the release of the second network tool, deja-packet, that I promised in my previous post. Here is the project description I submitted to Freshmeat:
“deja-packet transmits raw packets through a specified interface. In pcap file mode, deja-packet transmits user-selected packets from a libpcap capture file (such as one created by Ethereal/Wireshark, or tcpdump). In raw file mode, deja-packet transmits the raw contents of a file as one whole packet, and will exit immediately after the attempted transmission is complete (allowing deja-packet to be easily used in a script).”

‘deja’ like ‘deja-vu’, like, you’ve seen it before? Like you’ve seen the packet before? Get it? Yeah I know it’s hilarious.

See it here: http://www.frozeneskimo.com/electronics/network-tools/.

Network Tools section; pcap2c version 1.0 released

vsergeev — Thu, 21 Jun 2007 02:07:21 +0000

Recently I wrote a small network tool that I wanted release freely online. But, I didn’t know where to put it, since this is technically an electronics/embedded-development blog (not really for desktop programs). But, I don’t really have any other active development blogs. Oh well, I thought, and I decided to add a network tools section to this blog so I can post any other network tool programs I release in the future (I have one more coming for sure).

The first program released on the Network Tools page is pcap2c, which converts a pcap capture file to a C source file, or more specifically, reformat packets that are stored in a pcap capture file to more easily accessible raw unsigned char arrays. In some of the low-level network work I’ve been dealing with I’d had to retransmit certain packets I captured in Ethereal/Wireshark, and well, I didn’t really have a clean way to do it but extracting it of the pcap capture file, and rearranging it as a C array with perl. I would then compile the raw packet into a small PF_PACKET sockets program that could retransmit it down a particular interface. pcap2c greatly simplifies the process of extracting the packets, and will work with libpcap formatted capture files (Ethereal/Wireshark, tcpdump, etc.).

The next “network tool” that I will have available will read in all the packets from a pcap capture file in memory and allow you to retransmit any of them down an interface on demand. It’s basically a simple debugging tool that retransmits packets you may later want to observe as they traverse the network (watching them get routed, bridged, etc.). Future versions may allow you to edit the packet on the fly and automatically recalculate the IP and TCP checksums, but that’s down the long road, and there are already many projects in that niche.

Link to Network Tools section and pcap2c: Network Tools.

Any suggestions or comments are welcome at: vsergeev at gmail.

LC7981/HD61830 Driver for EL Backlit Samsung LCD

vsergeev — Sat, 31 Mar 2007 06:47:42 +0000

I’ve found the time to post this LC7981/HD61830 driver (only graphics mode implemented) and some images of this Samsung LCD I’m using. I bought the LCD off of ebay ( http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=230070938443 ) and shortly after I wrote the driver for it from scratch. I finished this driver about a month and a half ago, but I have just been too busy lately to post anything about it till now.

This is will eventually be a part of my GPS project, which I will get into later next week.

For now, here are the specs: an EL backlit 160×80 monochrome graphics LCD that supports text and graphics mode (I just coded for graphics mode and found a font/character pixel set online), controlled by an ATMega32. The LCD is driven by an LC7981/HD61830 controller (easy parallel interface). I’ll try to get the pinout up, including the EL connections with the inverter as soon as possible.

Pictures (no, I’m not running linux, the linux penguin just happened to be a convenient pixmap to demonstrate):

And the free source, currently coded for the ATMega32 but can be easily adapted to other uCs: avr-lc7981.tar.gz.

Alternatively, feel free to browse the images and source here: http://www.frozeneskimo.com/samsunglcd/.

USBasp Perf. Board Build

vsergeev — Mon, 19 Feb 2007 00:04:54 +0000

The computer I’m currently on (intel mac mini) doesn’t have a parallel port, so I can’t use the STK-200 style AVR-ISP to program/flash AVR chips. So, looking for the USB alternative, I stumbled across the USBasp. From the site, “USBasp is a USB in-circuit programmer for Atmel AVR controllers. It simply consists of an ATMega48 or an ATMega8 and a couple of passive components. The programmer uses a firmware-only USB driver, no special USB controller is needed.”

It’s cross-platform (Linux, Windows, Mac OS X), and since it implements USB as firmware in the AVR, it keeps the parts count pretty low.

I’ve gotten around to building the USBasp on a perf board, since I’m too cheap for a real pcb. I have confirmed it working on both Windows and Mac OS X (and as of today Linux too), and have used it extensively the last couple of days to write an LC7981/HD61830 driver on an ATMega32 (will post this up soon) without any problems.

There is also USBtiny, which is probably the fastest way to get up and running with USB AVR programming if you already have a parallel port STK200 clone. Like the USBasp, it implements USB entirely on the AVR firmware, but is actually more of a parallel-port to USB converter (it interfaces to an existing STK200-style AVR-ISP parallel port programmer).

USBasp Perf. Board Build - click for a high-res picture:

JTAG Wiggler Schematic Fix

vsergeev — Fri, 16 Feb 2007 00:17:29 +0000

Per has brought to my attention that the JTAG Wiggler schematic on the “JTAG Wigger Clone” page has an error. I jumbled up the P4/P3 connections on the parallel port when I was adapting the schematic in EAGLE (the schematic is based on this one http://jtag-arm9.sourceforge.net/circuit.txt). I have fixed this error in the JTAG Wiggler schematic image, and I also posted the EAGLE schematic file.

Thanks to Per for bringing up the error.
I apologize for this mistake and I’ll do my best to look out for them in the future.