View Full Version : Propeller Digital Dash?

11-17-2010, 03:47 PM
Hey Guys,

I have done work with Arduino and Picaxe in the past and would like to step up to Parallax. I was wondering with the integration of video, would it be possible take readings from the RPM sender, Vehicle speed sensor, Gas level, battery, water temp oil temp etc. and make a program to display the info on a lcd screen? Using the propeller?

11-17-2010, 04:30 PM
I sure think so. The video capabilities are up to the task. You've lots of options, with the RAM being the deciding factor on how it all goes. The task you want to start can be broken into little, modular bits, built up a layer at a time.

You could start with a basic dash, add a indicator or two, then build out the sensor portion. Once that works, it's just a matter of building out the other sensors, feeding data to what you've already got written video wise.

It's a very good project for Propeller, and how it works with blocks of code from the Object Exchange. Many of the things you want are already written, leaving you do connect them together, and supply some data.

11-17-2010, 07:09 PM
The propeller should work. The BIG headache is going to be interfacing with the vehicle.
Using the vehicle's OBD2 port would be the way to get all the vehicle data you could ever want. Another problem to watch out for, the are now different OB2 protocols.
The following link does a fairly good job of describing the differences.


11-17-2010, 08:37 PM
Actually, I did this a while back for a custom Ford Excursion that we built for an episode of Pimp My Ride.

It tied into the OBD-II port for a lot of the data and directly into a "sensor interface" module for the rest. (It was a bunch of ADCs in the interface module.)


11-18-2010, 12:11 AM
OBD1 & OBD2 interface chips
I'd think a prop could do the same thing.

Bob Lawrence (VE1RLL)
11-18-2010, 12:57 AM
Try this old thread:

see:OBD.zip (http://forums.parallax.com/attachment.php?attachmentid=64082&d=1254275866)


11-18-2010, 07:39 PM
This is a project I've worked on since leaving the BS2 behind. Right now I read the 0-12 square wave tach signal. Put it through an opto, then have an object from OBEX give me the frequency that I convert to RPM. I display RPM and MPH on two 4x7 LED displays. I think adapting it to a serial LCD may be actually easier than writing the MC14489 chip drivers that JonnyMac helped me with. The VSS signal is taken from a wire in my Toyota that I have the aftermarket cruise control hooked up to. It is a 3.3 volt square wave. I was running it through an opto too but the current draw of the opto was causing me to get a warning light on the dash indicating a power steering failure. Next I'm going to put 10K between the Yaris VSS and a Prop pin and try it again. I also have an outdoor temperature sensor for the third LED display but I haven't found the time to integrate that yet. Objects for the sensor exist that display to VGA. I just have to dumb-it-down to a compact, bright LED display. I also designed an analog display with 33 lites but still have to finish the software for a 32-channel controller chip.

11-19-2010, 02:23 AM
I've been working on a very similar project for my '07 4runner. I'm using an ELM327 as the interface to the ODB-II and using a propeller to parse and display the data on my Kenwood head unit. The head unit has a composite video input and the propeller drives it nicely. The 4runner uses the CAN protocol and the ELM327 handles all of the CAN messaging. I have the propeller send requests to the ELM and the ELM queries the CAN bus. I've attached a photo of the display in the truck.


10-03-2013, 04:26 PM
This is exactly what I want to achieve and the reason why i'm learning how to use the propeller microcontroller. Is there any chance you could post your source code? I Have already covered the OBD2-to-uart connection with the STN1110 IC (and several associated components) but I have no clue on how to start communicating with it or how to plot the results on the screen. Who knows, maybe I can develop the code a little bit further to add some gauges :thumb:

10-03-2013, 04:36 PM
Hello Ragametal - welcome to the Forum.

Please note that the last post in this thread is nearly 3 years old... and that two respondents haven't been on the Forum since.

10-03-2013, 04:54 PM
I noticed that the thread has not been active for some years but I figured that It couldn't hurt to ask for some help. Specially when somebody already came out with a solution that I can use as a basis for my project :)

10-03-2013, 05:47 PM

Try emailing the user. Click on their name to see options.

10-03-2013, 08:27 PM
I just did. Thank you very much for the advice. Hopefully Chefski is still around these forums.

10-03-2013, 08:29 PM
That looks like a pretty useful chip. I created a CANbus OBD-II reader using the Prop for all of the message formatting and just a 2551 for the level shifting. You don't need the drivers routines with that chip, but might find the higher-level routines useful.

OBD-II reader (http://obex.parallax.com/object/690)

Chris Savage
10-03-2013, 09:48 PM
I started a car computer project a few years ago that I haven't quite gotten back to, however in my Propeller based update to the original Z80 unit I have the 2 counters on one COG counting the tach and speed pulses for RPM, Odometry and Speed. I get odometry and speed from the same pickup. Signal conditioning is fairly straight forward and there are a lot of references for that. Odometry is displayed on a character LCD display that actually shows the digits rolling just like a mechanical one. Speed and RPM are shown on 7-Seg LED displays and for Fuel, Temp, etc. I will be using an 8-channel ADC and some conditioning from each sensor to measure those values as well, though I haven't gotten to that point yet.

10-08-2013, 12:14 AM
@ ChrisGadd: My car actually uses a different protocol (it is a honda). However the manufacturer recommended circuit for the STN1110 actually uses the MC2551 in order to enable the chip to communicate with CAN, just the way you are doing it.

@ Chris Savage: Your design seems a great fit for a project car or a race car. It is kind of convoluted for my use. I will like to make something practical that uses the hardware that i already have (OBD2 port and radio headunit with a 7" LCD screen). But i do appreciate your input.

I don't even have a propeller board yet since i 'm in the research phase. I decided to learn as much as i can upfront since this is my firs experience with electronics. I will keep all of you posted about any updates in my project.

Chris Savage
10-08-2013, 04:59 PM
@ Chris Savage: Your design seems a great fit for a project car or a race car. It is kind of convoluted for my use. I will like to make something practical that uses the hardware that i already have (OBD2 port and radio headunit with a 7" LCD screen). But i do appreciate your input.

My input was more to the point of it isn't too hard if you have the motivation and resources. My original ACM was Z80-powered (http://www.savagecircuits.com/content.php?47-Prototype-ACM-(Automotive-Computer-Module)) and I haven't yet gotten most of it transferred over to the Propeller yet. Good luck with your project though. It will be interesting to see no matter how you go about it.

10-14-2013, 08:45 PM
I am presently working on the same thing. tachometer portion is giving me fits, but hopefully I will figure that out! :)