While his wife was out-of-town [James] jumped at the opportunity to do some snooping around with her Chevy Tahoe’s parking assist sensors. We can understand how pulling parts out of someone’s car would make them none too happy. But we find it hilarious that it’s a leased company car he’s tinkering around with. But we’re glad he did, the ten-page write-up he published about the project is a fascinating read.
You can see the control board above which is housed beneath the passenger seat. It uses a Freescale microcontroller to read from the four bumper-mounted ultrasonic sensors. But just looking at what parts are used obviously isn’t enough to satisfy a hacker’s appetite for knowledge. [James] busted out a CAN bus tool to sniff the data packets. These sensors use a custom chip designed by GM, utilizing a single wire communications system. He figures out the communication scheme and builds an mbed based test rig to read them directly.
[via Dangerous Prototypes]
I’ve been meaning to give these a try in a project. They can be had on DX ( http://www.dealextreme.com/p/black-parking-sensor-radar-kit-dc-12v-24v-10283 ) for a reasonable price for 4 sensors so you don’t have to tear apart your car.
Nope, I don’t think those are the same type of sensors. The link you provided are to after market analog sensors. So, you’ll need a bunch of electronics to make them work.
The sensors I wrote about are Bosch OEM digital sensors.
Jim
I really want to see a write up about the OBDII bus thats used in cars. 🙂
There are hundreds of writeups on that, just google for OBDII hacking or a similar sentence.
Please don’t consider me a Troll on this but wasn’t this posted before? From the other site it was posted almost two years ago. And although the goal is to hack the system, based upon what I read; If you want to build a vehicle quality parking assistance system it might be easier to reinvent the wheel with an embed and an ultrasonic transducer like this one:
http://www.sparkfun.com/products/9009
And per the notes, you can control up to ten. So not only could it give you distance for parking, but perhaps also blindspot proximity warning.
But what do I know?
I think that James was prompted to figure out how they work because he hadn’t seen any hacks that reused GM sensors for non-automotive applications.
Your right on the money.
The automotive grade sensors are night and day better compared to the DIY robot sensors offered today. The automotive sensors are dang near indestructible in every sense of the word.
Now, if we could just find a cheap source for them other than digging through junk yards.
Nice work. I like the fact you did not get her permission. I used to disassemble (and try to sucessfully reasemble) my obnoxious ex-roomate’s beloved musical equipment while he was away on errands. It’s a rush when you hear the fool pulling into the driveway just as the last screw is torqued on his $2500 Roland box! Yes, I told him I did it as well!
I’m sure some creative mixing and filtering of the sensor outputs will allow you to do some beam shaping just like they do with radar.
So are the cheap ($5) add-on sensors from eBay likely to be compatible with the protocol described here, or is it something that varies by manufacturer?
The cheap eBay sensors are probably simple analog type. At best, there is a amplifier in the analog sensor to boost the millivolt echo return.
Using these sensors, your expected to generate the 150 volt by 40kHz ping voltage in your module to excite the piezo element.
So, the analog sensors are really cheap and really hard to use. That’s the beauty of using the Bosch sensor – ease of use. Only problem is finding Bosch sensors in the wild.
Good luck,
Jim
Anyone know how likely these sensors are to work under water?
For sure the Bosch automotive sensors are water proof. However, I have no idea what the sensor response would look like under water. Also, I think the center frequency is wrong for water. The Bosch sensor uses something close to 40kHz and everything I see for water uses something in the range of 200kHz.
This is a good writeup about ultrasonic:
http://en.wikipedia.org/wiki/Sound_from_ultrasound
jim
The system GM uses is an OEM version of the Bosch ParkPilot system. It is actually the most common park assist system in use.