I decided the bring some of the electronics gear in from the shop and put it on my workstation room. It makes working on circuit stuff much easier in the winter since I don’t have to heat the entire shop up just for an hour of hacking around. If I just added a MIDI keyboard this would be just like college!
Audrey and Kristin looking up at the tree, fire crackling, Bing Crosby in the background. I love my family.
Super duper super moon.
Another visit to Mauna Kea, the biggest telescope cluster on earth. The telescopes above the clouds. For the car guys, there is even a Subaru Telescope! I don’t see an EVO telescopes up here. 😉
[Note: The Subaru Telescope is in no way related to Subaru the car company. Subaru is a Japanese word for the Pleiades, an open star cluster in Taurus. The Subaru telescope is the national telescope of Japan]
Next round of interesting data, captured with my prototype ADCCAN. (EFR8374, 2008 STI)
Three boost settings (Wastegate, 22.5PSI, and 24.5PSI) with exhaust backpressure measurements. All three of these are still relatively low boost pressures, so the exhaust backpressure to manifold pressure ratio is not particularly high. It is typical to have exhaust pressure to intake pressure ratios of 2:1 to 3:1. Much above 3:1 and there must be some significant restrictions or the size of the engine is poorly matched to the turbine flow.
In the wastegate run, peak EGBP:IP was about 1.28:1. At 22.5PSI it was 1.32:1, and at 24.5PSI it was about 1.34:1. All of those are pretty low ratios, indicating adequate turbine flow. The really interesting data will come at higher pressures. The last graph show spool in each gear, starting at around the same point (~2000rpm). I have not done any optimization for gear comp, which would help a lot in 2nd gear. 1st gear is difficult to improve dramatically, but the solution there is launch control. With LC running I can be at 10-12psi before launching. I still need to get the compressor/turbine wheel speed sensor logging, which will be valuable to see at higher manifold pressures.
Development continues. With the analog capture and CAN interfaces done and working, I moved on to getting the SDCard interface configured. While it is great to log over CAN, I also want to be able to log to SD from the ADCs and from the CAN bus. When I made the board I put a set of SPI pins on a header so I could connect a MicroSD socket. (note I didn’t remember to put a pullup on DO which is normally open collector, but it appears the SD card itself has a weak pullup internally).
Interfacing to the SDCard over SPI has been an interesting endeavor. The SD-SPI spec is an odd one, with lots of goofy timing constraints. When you initialize the the card you have to start it up with 100-500khz SPI, then once it is initialized you can switch to a higher clock rate. And of course with SPI you send and receive at the same time, so if you are waiting for something, you are sitting in an transmit loop waiting for something that looks like data to appear.
The PIC I am using (dsPIC33) only supports SPI speeds up to 15MHz SCLK (according to the datasheet), although I was able to get it working at 20Mhz SCLK. With single wire SPI, using single block writes (which have a lot of overhead) I am getting about 640KB/sec, or a bit over 5Mbit/sec. That is more than sufficient for my use case, as even with 24 channels at 1000 hz we are talking about writing 240KB/sec maximum write speed.
For running this on my desk I was using an inexpensive 12V wall wort, and when I looked at the output I was surprised. (see last picture).. 250mv noise that is just terrible. I have similar noise on the +5 and +3.3V rails, which means I don’t have enough filtering on the power regulation side. The 12V source in a car can be much worse, so I need to look at adding some LC filtering. I’ll finish up my SD interface, then get working on overlaying a FAT16/FAT32 filesystem implementation.
Thanks to Matthew R. Wilson for the help debugging the clock signals!