Tag Archives: AVR Programmer

Project Updates

A few small updates on the state of various projects..

NTP Server: Version 1.5 board looks mostly final now. The 3.3V switchmode regulator design has been checked on a breadboard and seems to run 1.4 just fine, so we’ll be going with that on the 1.5 board. This will reduce the heat significantly, as the reverse-polarity diode (which itself loses about half a watt) is being replaced with a P-channel MOSFET and the switchmode supply loses far less heat compared to the linear regulators (almost 1.6W are sourced from them alone). Software side I’ve removed all the (hugely problematic) single precision floating point code and use the time reported in integer milliseconds instead. Much nicer!

AVR Programmer: First build has been completed, and it largely works with the LUFA code compiled and uploaded into it. Various issues have come up, such as the bootloader switch not working quite as expected (The bootloader will only enter DFU mode if the switch is closed and we’re coming out of external reset which isn’t just a power-on-reset. Ick.) External flashing of the MCU doesn’t work right (unsure why) and it seems to hold !RESET low on targets. There is a 1.1 which is in progress.

New Breadboard PSU: Following on from the tests on the new switchmode supply for the NTP server, I’ve sketched out a new breadboard PSU which uses the same design. This would be an alternative to the linear one I already make and sell. At the moment it’s a single output design, I’m thinking about ways to make it dual-output or at least easily switchable between 5V and 3.3V.

XMEGA Arduino: Most of this design is completed. I need to just do a build to see how it plays out. The new XMEGA C3 line looked interesting but imposes some annoying routing problems. While using the C3 would provide a USB XMEGA which isn’t encumbered by crypto modules (and, therefore, export regs) and the C3 has USB pins where they are on the AxU chips, it has the same selection of peripherals as the D3 and USB is camped on top of one of the SPI ports. Which makes routing hard. May stick to the D3+MEGA16U2 bridge approach for now.


New boards have arrived!

The new revision of the NTP Server and a test build of the LUFA AVR Programmer boards have arrived. The service from Seeedstudio was pretty quick and excellent for pricing, although one of the boards had some drills not correctly done. Still, it’s far cheaper than getting larger runs made so I am quite happy.

Sadly, I appear to have made some mistakes with the stencils that were cut by Ponoko – the detail has been lost a lot more than previous cuts. I suspect I didn’t take into account laser kerf enough, but I also think they were cut without protective paper on both sides as previous ones were done. That seems to make a lot of difference. I shall get them re-cut in the next few days.

Now off to order more parts from Element 14 to prepare for the first builds of these new designs!

New boards on the way

I finally committed to a new set of boards for a couple of projects. NTP Server 1.4 and the LUFA-based AVR programmer both have been sent off to be manufactured, and assembly should take place in a few weeks time. I’ll separately post about the changes for the NTP Server.

The LUFA board is an quick prototype to see how badly I’ve misread the USB AVR datasheets. It is based off the hints provided in a readme associated with some LUFA code, and vague attempts to read the USB sections of the Mega 16U2 datasheets. It includes a level shifter to support 1.8 – 5V targets which covers all the useful ranges of both Mega and XMega MCUs.

I’m not sure how the little LUFA board is going to turn out, but it was fairly cheap to get made and I’m bound to learn something out of it as a result.

These are the first boards being made by Seeedstudio’s Fusion PCB service, which for very short runs looks cheaper than previous options. It’s only 10 boards (compared to the 25 or so I was getting from other runs) so it’s more expensive per board but much cheaper to do a run because it’s a smaller number of  boards. We’ll see how they turn out.