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Month: January 2019

House

House

Some subflooring is starting to materialize. Those 1&1/8 T&G plywood sheets are pretty heavy. The sheeting should be done today, then more floor joists over the mechanical room and storage room, plus all of the floor joists over the deck.

Reflow Oven

Reflow Oven

Reflow oven completed, calibrated, and ready for a board.

I did the ‘learn’ cycle which helps the software determine the PID constants for all three heating elements, as well as judging how well you built the oven.

Heat leakage is very small, and at 400F internal temp the outside skin was only 85-96F.

I ran several test ‘reflow’ cycles using the leaded 225F profile, and the graph below shows the performance using both the controller’s thermocouple, plus two thermocouples attached to PCBs in the oven.

The PCBs (and the tray) have much more thermal mass so you can see the lag as the soak cycle starts up, but the overall curve is great, and the PCB gets right to the programmed peak temperature.

The Orange vs Green represent the sensor at the center vs the very edge. These kind of ovens sometimes have problems with reflowing boards at the edge while not cooking board at the center. The difference between the two is about 5 degrees C, which is well within the reflow temperature region.

Next up I’ll paste some boards, install some parts, and reflow.

Reflow

Reflow

In order to test this reflow oven, I designed a small board which will also help in doing some testing for a few other projects. Very simple board – 3.3-6V power input, SWD Debug port, Console (LPUART), 8 UARTs to connectors, Both FD-CANs thru a transceiver and exposed. 4 Buttons and 4 LEDs on digital ports, 3″ x 3″ board. Caps/Res/LEDs are 1206s because I have some here and they will be easy to hand place.

Anything stupid?

I use the ST Appnote for this series for layout and power/clock setups: https://www.st.com/content/ccc/resource/technical/document/application_note/group0/e8/d8/d0/32/33/94/41/dd/DM00337873/files/DM00337873.pdf/jcr:content/translations/en.DM00337873.pdf

STM

STM

I did a little digging based on Clay Cowgill and Christopher Neil Bradley’s suggestion to look at the STM32H743, and indeed that looks to be a great choice for a processor. It is an ARM7 core with FPU, runs at 400MHz and 856 DMIPS, has both single and double precision floating point (many of the M cores are single precision FPUs only), and has a TON of serial ports. 4 USARTS, 4 UARTS, and 6 SPIs.

I did two different design layouts, looking at the pin mappings to see if I can make them work, and make the physical layout easy. I did one design using UARTs as UARTs (asynchronous). In that configuration I was able to get 8 UARTS on each chip such that each CPU could be connected to the nearest 8 neighbors (side to side and diagonal). Since it is in a UART config, only 2 pins per connection, and it is bi-directional and full duplex. That also allows an additional 4 direct digital connections per node connection ( which could be used for some kind of barrier synchronization, or another transfer protocol. The upside of that architecture is more connectivity, the downside is figuring out has fast I can run those UARTS. Since I am only going a few inches, I suspect I can run them at the maximum 10mbit speed that is supported by the UARTs.

I did a second design where I used 2 SPI channels between each neighbor (only 4 neighbors and 8 SPI channels). The primary reason for that is because with SPI, only one side is driving the clock, so if the other side (the slave) wants to transmit something, it has to wait for the master to send something ( and thus drive the clock). Most people use an additional digital line to signal that (which could drive an interrupt), but that is a huge amount of processor overhead just to send a single byte… and it makes the efficiency not uniform. Using two SPIs interfaces means each one is driven by each side, and as an added bonus there can be two simultaneous transfers in both directions. The SPI ports can be driven at up to 50MHz, which would be a significant boost in potential transfer rates.

These chips are TQFP-100s, with 0.5mm pitch, so not something I would want to hand solder a lot, but in the realm of home reflow for sure.

I am still exploring the FPGA soft core option.. but of course it is almost impossible to find any recent FPGAs that are still QFP packages. Almost all of them are BGAs.

House

House

More walls have appeared and floor joists are being installed. Once the first level floor is installed, the upper
walls will go up quick. The shop looks quite tall from the inside. It is only a couple of feet more than my current shop ( 14.5 feet vs 12 feet), but that is noticable.

Clearly I will need a forklift.

House

House

The last couple of weeks were a bit slow on the house front. Cold and lots of wind on site.

Some of the floor joist i-beams were delivered, along with some other joists and boards.

You can see they have started to put up plywood, and due to wind they will probably try to get most of that done before starting on the joists.

With Audrey to scale, the shop certainly looks to be a good size.

Billet

Billet

Oil pickup, baffle, and pan installed. Thanks to Killer B for making cool stuff for a cool build.

Wine

Wine

Wine is an interesting drink. There is so much variance across different wines in terms of taste, as well as a tremendous variance in price. While I ignore most of the fluffy descriptions of ‘coffee with a hint of rare berry from the third bush on the left’, it is something interesting to try to understand and appreciate.

I am by no means a wine expert in any way, but I do have a like for some particular styles. I tend to like lighter wines, and Bordeauxs in particular. Tonight we had a wine for a birthday dinner that was just fantastic as an example of a great Bordeaux. It was a 24 year old first growth from Haut-Brion. It was second only to a 1990 Margaux we had at new years. Both excellent Bordeauxs.

The really interesting thing is when I compare it to other much less expensive ones. A few months ago I had a 2005 Bordeaux from Ch√Ęteau La Vieille Cure, which is a wine that is about 1/10th the cost of the other first and 1/20th the second. It is different for sure, and when I have done a few limited blind tastes, I could tell which one I like better, but nothing more specific than that. There are famous tests that have demonstrated to difficulty of rating taste, but equally the difficulting in not telling the difference. In the end they key is to find what you like… unless what you like is a 90 Margaux, because that is not easy to find at your local grocer.