VE7XEN's electronics blog

Programming the ATtiny841 with avrdude

Working with my good friend Daniel McLaren on a cool interactive art project, I designed a board around the ATtiny841, which is a nifty new entry to the AVR portfolio. Unfortunately when intial power up of the board was successful, I found I was totally unable to write code to the device with avrdude as I normally would; the chip is unsupported in even the latest version. I found a helpful post on AVRFreaks with a code listing for avrdude.conf that was purported to work, but I found it produced verfication errors (and a non-working chip) every time.

After much mucking around and recreating the part in avrdude a dozen times, I got it to work.

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eBay AD9850 board performance testing

Prompted by user Skimask over on the eevblog forums, I undertook some performance testing of an AD9850 module, readily available from eBay (search 'AD9850 DDS') for under $10 shipped. These are advertised as 0-40MHz devices, and appear to include the datasheet-recommended 5-pole output filter and a 125MHz canned oscillator. Measured distortion and spurious performance is excellent, especially for the bargain-basement price. Skimask was curious about the performance at audio frequencies, so I undertook some measurements at 1KHz and 5V. Read more →

Project Start: tinyCounter low power HF frequency counter

I've ordered myself an EA3GCY ILER-20 kit, and being a single-band QRP hand-tuned radio, I want a convenient counter. I'm going to be using this in the field on battery power, so it's got to sip the juice and be small (tiny!) and light. The design should be suitable for any small HF rig (and maybe 6 metres) with an easily accessible point to measure the VFO. I put together a design and just ordered PCBs. Read more →

DIY 50Ω dummy load w/ peak detector

Having ordered a used mobile radio from eBay, I felt that I needed a dummy load for tuning and testing. While I was at it I figured I'd add a peak detector to get a reasonably accurate power measurement at the same time. I pulled two bits of heatsink that came from an old PC power supply, an AC filter capacitor and a couple of signal diodes from the junk bin. Read more →

Clock-Block Knock Off

A while back I spent some time building a stratum 1 NTP time server based on a Motorola Oncore UT+ GPS receiver and an old (decommissioned and free) PC Engines WRAP.1E-1 board. I was inspired by N8UR's (John Ackermann) essay on using the Soekris net4501 single-board computers as high-accuracy time servers, which I don't have - but I thought I'd do what I could with the WRAP. I rigged up a level converter and hooked the Oncore up to the WRAP's serial port, installed FreeBSD and got it up and running keeping good time. Read more →