2010-05-16, 19:20 CEST
GPIBtoUSB: Built the prototype on breadboard (you can use 11 MHz crystals on breadboard...), and tested it successfully, transferring some screenshots from the scope to my notebook, and converting it to PNG. See the project page for examples...
2010-04-14, 20:45 CEST
UPSMon: Found and fixed the cause for the missing characters on UART reception: Classical race condition between one global status bitfield vs UART and timer interrupt service routines. ISRs now have their own status byte each, and changes to this are protected by disabling interrupts for the bit toggling.
Remark for the occasional reader: status |= BITMASK; is one instruction in C, but becomes three instructions in assembly - load from RAM, logical operation, store to RAM...
2010-04-12, 23:30 CEST
UPSMon: Found and fixed a bad solder joint on the FT232, leading to random errors in USB enumeration on connect. Instrumentation of the UART RX ISR showed that the missing characters mentioned before are not caused by oscillator drift, as the ISR is called in cases where there is no character echo. However, no echo is seen on the AVR's UART TX line... So something seems to be wrong in the firmware's UART handling. Further investigation needed here...
2010-04-06, 12:10 CEST
UPSMon: The circuit sometimes does not echo back single characters received over the USB serial interface. Investigation showed that this is not an issue of missing flow control, but the characters seem not to be received by the microcontroller firmware... The signals coming in from the USB interface IC are exactly the same for "good" and "bad" cases, so this might be either a firmware issue or a result of the internal oscillator being used in the MC, and operating frequency drifting.
I will instrument the RX ISR in the firmware to indicate reception to see if the hardware UART receives those characters correctly.
2010-03-28, 20:00 CET
UPSMon: Produced another PCB... The one I made last weekend had been scaled to fit an A4 pagesize by xpdf, which I used to print the etch mask -- unfortunately, it was not meant to be scaled down, and very unfortunately, I did not check the size before etching the board. I therefore had to make another one (without scaling), which is now already stuffed with components, soldered, and tested to work well. More documentation and photos to follow...
2010-03-21, 19:00 CET
UPSMon: Produced PCB. SMD pads for the USB interface are slightly tinned (with "Rosol 3", see PcbProduction for more on that), and the whole thing is coated with rosin spray. The case will be made from an Altoids box, which is a very traditional project box...
2010-01-11, 00:50 CET
EloInv: Added EloInv project to the Mantis bug tracking tool I use in preparation for publishing this project. Category support added over the weekend, providing finer-grained description of parts than the "type" field provided so far. "Type" classification will stay, though, as I am using it for partlist import, labeling and displaying of parts. In the future, these functions could also be done with abbrevations stored in the category table - though I have not really thought this through so far. For now, "type" will stay, period.
2010-01-10, 17:00 CET
Schiesstakt: "Mode" button has been added. After this, the device did not work any more - due to a contact issue between the two LEDs, GND at the microcontroller was at +1.5V (with respect to "real" GND at 0V). Fixed this issue, so the device is working now and shall be tested tomorrow evening on the shooting range.
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Last year's news are in ProjectsBlog/ProjectsBlog2009.
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