I got it! "I agree" killer! Cheap, easy, but...

[naterprius]

To V8CobraKid:

Hah! I got you fooled...

If I really knew my stuff, I'd post instructions on how to modify the code on your NAV disc to remove the "I agree."

;-)

Nate

[V8Cobrakid]

you have proper ideas of how to figure it out. I have a lot of knowlege on items myself.. but i don't quite know the things you know.

[naterprius]

Well, in that case, thanks for the compliment. As far as having the right ideas, they come from questions, either my own, or from others. As Einstein put it, the question and the answer are really not different at all, rather the same thing.

For me, this one was: "Every time I turn on the NAV system, I have to push "I agree." How can I avoid having to do this?"

The answer was in the question itself, leave the NAV system on!

My point is, if you think of a question, post it! (perhaps after reading the previous posts to save on the repeats).

Even contributing to the forum in the form of a question is worthwhile, it may provide the answer someone else is seeking.

Nate

[naterprius]

Well, I got impatient, and wanted to check the parasitic draw. Without the mod, it's around 20 milliamps (specified limit for a generic car is generally accepted to be around 50 milliamps).

With the mod, it's around 350 milliamps, even after the DVD drive spins down. This level is right at the edge of problematic. I'm uncertain if the Prius' smaller battery has smaller capacity when compared to larger car batteries.

Even if this mod never causes the aux battery to go totally dead, it would likely reduce the lifespan of the aux battery; it would "die for good" at an early age.

I'm on the fence on this one; I may go with this mod anyway.

Nate

[TonyPSchaefer]

Nate,
Your attempts as the hack are very intereseting. I am curious as to your discoveries on the DVD coding. However, without being reminded every time you get in your car that it's danerous to not watch the road, aren't you concerned that without the [I agree] button you might find yourself staring at the map too much?

*waits patiently to see if anyone thinks he's serious*

[naterprius]

Tony, I have now been in 87 seperate collisions since I made this modification. A total of 31 people have died and 47 severely injured. Most of this was caused because the GPS system told me to drive on the sidewalk, so I did, and I have run over quite a few folks that way. A few have been caused by driving on the wrong side of the road. Still others were caused by me ignoring stoplights that were not indicated on the NAV system. The worst one by far (22 casualties) was caused by the time I somehow got the system into "French" mode, and was not given the option to select "English" when I first tried to use the NAV system on that trip. Vou le vou coushay avec moi?

Regardless of this, I am certain that everyone agrees that none of this is my fault, and a lawsuit against Toyota is in order. Perhaps this will encourage the voice command system in the next generation of vehicles to read aloud the legal disclaimer everytime one presses the "voice command" button. This would truly make our society safer.

Nate

[naterprius]

Seriously, I've decided to leave this mod in place for a while. To add to the experiment, the car doesn't roll much these days since I'm home on leave with my new daughter. We'll see if I go out one day next week and the battery is dead.

350 milliamps is too high, but we'll see what the detrimental effects are.

Nate

[brosnan]

Nate - Just noticed this thread - glad you tried this. The auxiliary battery powers the Nav unit when the car is off. It's rated at 28 Amp hours. If we assume that using half that capacity will drop the voltage below the operating level of the Nav ECU, you've got about 40 hours @ 350mA to still maintain your "I agree" state. And probably about 50 to 80 hours before you have trouble starting the car.

Too bad it's not a bit lower current after the disk spins down. Evan's suggestion of powering up just part of the circuit's a good one, but I think we'll have trouble separating the the sections of the nav ECU. Most likely the I/O lines common between sections will provide parasitic paths for keeping power alive even to sections we disable (unless dozens of lines are cut).

I looked at my photos of the guts to see what kind of processor they use. Unfortunately the likely culprit is an Application Specific IC marked Denso Naviem. If you google that, you'll find references to an embedded Toshiba TX49 CPU. The TX49 core is based on the MIPSTechnologies, Inc RISC design. There are references to 2 possible operating systems (uITRON and MS Windows Automotive). It's not clear whether any of these comments apply to the Prius nav system, but most likely the bit which gets set when we press the "I Agree" button resides in a RAM location in an embedded processor inside this Naviem chip.

This Japanese web site: http://response.jp/feature/navi_2002guidea...122_11_024.html shows a similar Naviem part # and says it's got a 64 bit 200MHz RISC CPU on an 0.18um process with 3D video processing engine, GPS engine and VRAM all on one chip. There are also 2 Samsung 64Mbit SDRAM (K4S641632F) chips near the Naviem. There's some chance the "I Agree" state is stored in this memory (160mA refresh current on the data sheet). Or maybe firmware is loaded from the DVD and executed from the SDRAM.

[brosnan]

Here's a thought - most of us probably drive our car at least once a day most of the time. It sounds like we would not drain the auxiliary battery too much each night by leaving the Nav ECU powered up in that case. Each time we go on a drive, the battery will be recharged. And we won't have to endlessly "agree" on each trip.

So the real problem comes when we don't drive the car for a few days. How about we just build a timer which keep the Nav ECU powered for a maximum of 24 hours (for example) and then shuts it off? It could alternately just wait for the auxiliary battery voltage to drop to ~10 Volts, then turn off the Nav ECU. Either way we won't unduly drain the battery and we'll greatly reduce the number of times we need to press the "I agree" button.

By the way, I estimate that by leaving the nav powered all the time wastes the equivalent of about 0.01 gallons of gas per day, if I did the math right. In other words, recharging the auxiliary battery each day to recover the overnight drain will consume an extra 0.01 gallons. So if you drive 20 miles a day, your mileage would be reduced about 2% by leaving the nav powered all the time.

[naterprius]

Drove the car last night for the first time since implementing the mod. Started right up, no issues. That makes over 40 hours plus all the extra power I drew messing around for a few hours before.

Not bad. Maybe the draw fell quite a bit after it sat for a few more hours. I'll keep everyone posted.

By the way, with all this talk about voiding warranties, this one could void your warranty on your aux battery; that is, if your car dies, and needs to come in for service, it's likely because of this mod, and you might have to pay for the repair.

Nate