Controlling the Instrument Cluster's Display

74946 Views 470 Replies 65 Participants Last post by Mario, 1 mo ago

Mario

Discussion Starter · Nov 9, 2015

A little project I'm working on.

(Sorry for the horrid picture!)

Here's the elevator pitch: Directly control the LCD panel with a microcontroller to display custom information on the instrument cluster. The microcontroller will also read the data that would normally be going to the LCD and can choose to display that info or custom info.

Maybe you want to display OBDII parameters where the MPG is. Maybe you want to change the charge, assist, and SOC gauges to accurately reflect amps in/out, real battery SOC, etc.

I've got a few other ideas as well. Once I'm finished with this project I'll open-source everything I've learned and perhaps produce some PCBs to sell. We'll see!

I have work and other projects as well, so it may be slow going at times. But I'll try to give updates fairly regularly.
I don't think this has ever been done before. I hope you guys are excited!
If anybody is or wants to work on something similar, I'll be glad to share what I know; just ask.

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Reactions: 5

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mudder

· #61 · Jan 5, 2016 (Edited)

Mario said:
The instrument cluster already has a 100 ohm resistor across the two lines, so I wasn't planning on adding one. From Honda's design it's clear the cluster was never intended to send data, only receive it. But I think I might be able to make it work.

100 ohms is pretty low - I'd wish it were higher. Unfortunately, I can't expect a user to replace that resistor. It's surface mount, and it could cause some issues with a stock BCM if it were changed. I'm not sure we'll get good transmission with 220 ohm series resistors on the lines. I think you should probably switch to a 100 ohm termination resistor to match the stock setup.

There shouldn't be bus contention anyway because Pegasus will be a slave device - it'll only send anything if you send it something first and are waiting for a response.

I didn't know the instrument cluster already had 100 Ohm termination. I agree 100 Ohms is low... the OEM MCM is driving 50 mA into METSCI. Interestingly, the minimum guaranteed driver output current is only 35 mA, so Honda is using the LT1487 above the linear specification.

Also, from the datasheet, loading the LTC1487 to 50 mA drops the differential voltage to just ~1.65 V typically. LTC1487 only requires 200 mV magnitude between A,B for guaranteed signalling. I hesitate to add any more termination resistance because Honda is already driving the LTC1487 out-of-spec. However, leaving my side floating will almost certainly prevent you from reliably communicating with me (I'll 100% be able to communicate with you, as OEM).

I'll add a SPARE parallel termination on my end and remove the series resistors I mentioned previously. Maybe you can talk to me with 2 kOhm termination on my side... we'll see

.

Mario

Discussion Starter · #62 · Jan 5, 2016

mudder said:
I didn't know the instrument cluster already had 100 Ohm termination. I agree 100 Ohms is low... the OEM MCM is driving 50 mA into METSCI. Interestingly, the minimum guaranteed driver output current is only 35 mA, so Honda is using the LT1487 above the linear specification.

Also, from the datasheet, loading the LTC1487 to 50 mA drops the differential voltage to just ~1.65 V typically. LTC1487 only requires 200 mV magnitude between A,B for guaranteed signalling. I hesitate to add any more termination resistance because Honda is already driving the LTC1487 out-of-spec. However, leaving my side floating will almost certainly prevent you from reliably communicating with me (I'll 100% be able to communicate with you, as OEM).

I'll add a SPARE parallel termination on my end and remove the series resistors I mentioned previously. Maybe you can talk to me with 2 kOhm termination on my side... we'll see .

Well, it's pretty much the typical application shown in the datasheet, but using 100 ohms instead of 120. The waveform they show is pretty rounded, but it appears to work okay (and with 2000ft of cable, too!).

And while the minimum current-driving capability is 35mA, the max is 250mA, so I think 50mA isn't too bad a gamble.

I agree, let's try 2k on your side and we'll have the stock 100 ohms on my side. Once I get the board and everything I can set up a dummy receiver with 2k termination and look at the waveforms on a scope.

Mario

Discussion Starter · #63 · Jan 10, 2016 (Edited)

Been working on the PCB layout, here's how it looks so far:

All the component locations are pretty much final, though I might still tweak them a little. Just need to finish up the routing now, put all the designators in the right spots, and add some art! Should be done before too long, then I'll order the PCBs.

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eq1

· #64 · Jan 10, 2016

wow, only 2 pages at 40 posts per page and you've already got a pretty lookin' computer board thingamajig...

mudder

· #65 · Jan 11, 2016

Looking good, Chris!

Mario

Discussion Starter · #66 · Jan 13, 2016 (Edited)

2

More layout progress! It's almost done now, just a couple more connections to make.
Edit: Forgot to say, I am using all but one pin on the microcontroller! I need 50 GPIO and it has 51. Almost feel like I should add just one more thing.

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mudder

· #67 · Jan 14, 2016

Any thoughts on pricing yet?

Mario

Discussion Starter · #68 · Jan 14, 2016 (Edited)

mudder said:
Any thoughts on pricing yet?

Since this is a project I wanted for myself, I'm not going to charge for my time to develop the thing. I was going to make it anyway! So the price for somebody else to get one will just be the cost of the PCB fabrication, assembly, and parts, my time for making the custom OBD-II cable and joystick cable + board, and shipping it all.

It really depends on how many I expect to sell. I got a quick quote from a local PCB fab house that I use often for work. If I get 50 made, the completed boards come out to about $100 each. I'm not sure I'll sell that many, though, and I'm hesitant to get that many made. 20 would come out to about $150 a board. Then you need to add my time for assembling the OBD-II cable and joystick board + cable. Another $50?

I think we're looking at $200-250 for me to feel it's worth my time. If I could get 50 preorders, I think I could sell them for $200 apiece.

eq1

· #69 · Jan 15, 2016

Maybe you should do a little synopsis of the device once you know exactly what it will do and that it will do it, kind of a summary, including a few words about how to install, and then do either a head count or some kind of pre-order, maybe with a few target prices? That way you'll have a better idea how many people will buy one (or two)?... From what I've read, I'm pretty sure I'd pony-up $200 for one... My guess is that you probably wouldn't have any problem selling 50 of them, but it may take some early adopters to try it and prove that it works and that it's cool... Ask Peter how many OBDIIC&Cs he sold - I'd say that'd be near the number of Pegasii you'd be able to sell...

mudder

· #70 · Jan 15, 2016

I'll early adopt that. Send me your paypal and I'll make a 100% deposit, knowing that the price might increase. Having an early unit will help me suss out Linsight+Pegasus.

Sigma Projects

· #71 · Jan 15, 2016

this is so awesome, looking forward to your final product.

retepsnikrep

· #72 · Jan 15, 2016

'ill have on as well... Willing to put money where mouth is.. I like to support new projects..

Darkfish

· #73 · Jan 15, 2016

Im definitely in for at least one, if not two Mario.

-Steve

nachoshahaha

· #74 · Jan 15, 2016

Put me on the list too. Thanks Mario!

IamIan

· #75 · Jan 16, 2016

+1 add me to the list.

And

+1 Appreciate time and efforts.

albert247

· #76 · Jan 16, 2016

Willing to put money where mouth is.. I like to support new projects..

I am in agreement . have been following this thread as well.
I would like to be added to list when the product is ready.
Thanks Mario

Mario

Discussion Starter · #77 · Jan 16, 2016

Thanks for all the interest, guys! When the time comes, I'll make a topic so everybody can pre-order one and I can see how many I can expect to sell. Looks like I have at least 6-8 so far.

Eq1, while the OBDIIC&C is a good comparison, I think it sells so well because it's just plug and play. You have to take your instrument cluster out to install Pegasus, so there is a larger barrier to entry. But we'll see how the preorders go.

Another feature I was thinking of - average speed for trip meters. I want to know this, especially on long road trips. 60mpg is impressive - but knowing it was 60mpg at an average speed of 75mph would be even more impressive! This should be easy to implement, just start a timer whenever a trip is reset and the calculation is easy, just miles traveled divided by how long it takes. It would pause counting while the car (or engine?) is off.

IamIan

· #78 · Jan 16, 2016

Mario said:
Another feature I was thinking of - average speed for trip meters. I want to know this, especially on long road trips. 60mpg is impressive - but knowing it was 60mpg at an average speed of 75mph would be even more impressive! This should be easy to implement, just start a timer whenever a trip is reset and the calculation is easy, just miles traveled divided by how long it takes. It would pause counting while the car (or engine?) is off.

Me Like.

Calpod

· #79 · Jan 16, 2016

Put me down for one.

highwater

· #80 · Jan 16, 2016

One more

Randall

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