UDP Between STM32-F4 Discovery Boards

February 15, 2013 by Mike Szczys 24 Comments

stm32-f4-udp

[The Backwoods Engineer] tested out a new accessory kit for the STM32-F4 Discovery board. The image above shows two boards communicating with the UDP protocol. Notice the extra PCB into which each Discovery board has been plugged. This is a third-party add-on which adds Ethernet, RS-232, SD card slot, and a connector for LCD or Camera. We’ve had one of these F4 Discovery boards on hand for a while and haven’t figured out a good way to connect external hardware to the huge dual pin-headers. This doesn’t solve the problem — the base board also includes dual headers to break-out all the pins — but having Ethernet, serial, and SD certainly reduces the need to add all that much more. The other drawback to the hardware is that the sample firmware is targeted at the IAR Embedded Workbench which is neither free, nor in the realm of affordable for hobbyists.

The NIC used on the baseboard has auto-crossover capabilities so the boards were connected using a regular Cat6 patch cable. This example has the boards constantly sending UDP packets with the module on the right reporting status information to a terminal via the serial connection.

Cracking Open A 24-port Switch So You Don’t Have To

February 15, 2013 by Mike Szczys 14 Comments

hp-procurve-ethernet-switch-teardown

[Kenneth Finnegan’s] post about this 24-Port HP ProCurve 2824 Ethernet Switch teardown was a delight to read. He’s taking an introduction to networking class at California Polytechnic State University. One of their labs included virtual machines shooting thousands of new MAC addresses at the thing all at once. Despite it’s ability to switch data at a blazing fast rate, it’s ability to deal with that many new hardware identifiers was less than impressive. He wanted to find out why and it just so happened he had one of these in his parts bin at home (which he refers to as if it’s a high-powered RPG character).

The mainboard is divided into three major blocks: the power supply, the switching hardware, and the processor that makes this a manged switch. Although he covers all of these pieces (and the switching stuff is very interesting to learn about) it is the processor section that was causing the aforementioned slowdown. It’s a 266MHz PowerPC chip with a measly 64 MB of RAM. Of course this doesn’t need to be any more powerful since all traffic from previously ‘learned’ MAC addresses gets handled by the switching block and never touches the processor portion.

Don’t miss the end of his post where he discusses how the filtering caps, and semi-isolated ground planes help to tame the beast created from all of this high-speed switching.