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Old 16th January 2013, 21:30   #1
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Default Memory retention of tuning parameters & clock in a Head-Unit

My first question is about the memory retention in a HU using the car battery and the second query I will come to later is a corollory to my first query. First the background--- I recently bought a Chinese double DIN HU for my Estilo (at a dirt cheap price through eBay) with 7" touchscreen, DVD, GPS etc. to replace the Pioneer single DIN I had for the last 3 years. The Pioneer had it's yellow and red supply wires shorted and going to the ACC switch (not the regular yellow wire going to the battery directly). This I had to do as I found that the drain through the yellow wire was considerable and the battery would be flattened if I did not use the car for a couple of days. With this experience in mind I decided to check the battery drain through the yellow wire in the chinese unit before installation. With a 12V power supply I could measure the current drain through the yellow wire to be 100 mA which I consider to be very high and would lead to a flat battery in a very short time. And now my query-- in this day of Real Time Clocks with Clock and static RAM memory kept alive by coin cells and Non- Volatile memories available (I am basically from the Consumer Electronics field and have worked on TVs which had non-volatile memory for storing the tuning parameters even in the early 1990's) why does a HU memory require such a high current to retain the parameters? Can some one enlighten me on why Non-volatile memories or Real Time Clocks are not used in HU's. This has me stumped probably because I am looking at this from a Consumer Electronics viewpoint and not from the Automobile Engineers' s viewpoint. My second query is ---- In this Chinese HU (Win CE 6.0 based) when powered up, by default it goes to the tuner mode and as the tuning parameters are not retained there is a continuous hissing which I have to mute and then switch on the GPS. Can anyone tell me if it is possible to hack it so that when powered up it goes to the GPS function by default?
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Old 17th January 2013, 12:24   #2
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Default re: Memory retention of tuning parameters & clock in a Head-Unit

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Originally Posted by nitnab View Post
... The Pioneer had it's yellow and red supply wires shorted and going to the ACC switch (not the regular yellow wire going to the battery directly). This I had to do as I found that the drain through the yellow wire was considerable and the battery would be flattened if I did not use the car for a couple of days. ...
Wrong wiring. Wonder who did that wiring - even your Pio would have lost settings every time you switch off ignition. Yellow should be BAT, Red should be ACC (ignition switch). If both Yellow and Red are connected to ACC, there will be no power to the HU to retain any settings.

Don't worry about drain - 100mA draw is 1.2AH per hour. Your battery can sustain it for a day at least. ('Dirt cheap' - they don't expect you to complain of battery drain ). But, I also think 100mA is unusual, and this means that the CPU is not going to 'sleep'. With Ignition off, the consumption is expected to be <10mA.

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Originally Posted by nitnab View Post
... in this day of Real Time Clocks with Clock and static RAM memory kept alive by coin cells and Non- Volatile memories available ... Can some one enlighten me on why Non-volatile memories or Real Time Clocks are not used in HU's. ...
Cost and maintainability:
* Unlike consumer equipment and PCs, it is impossible for User to open the cover and replace the coin cell
* NV-RAM / EEPROM is a costly piece of hardware - too high % cost of unit cost
All retention objectives are met with the mechanism of ACC - the hardware can go to low-power mode, since the battery is always connected.

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Originally Posted by nitnab View Post
... My second query is ---- In this Chinese HU (Win CE 6.0 based) when powered up, by default it goes to the tuner mode and as the tuning parameters are not retained there is a continuous hissing which I have to mute and then switch on the GPS. Can anyone tell me if it is possible to hack it so that when powered up it goes to the GPS function by default?
That board must be using HU conventions, not computer conventions - and doesn't have non-volatile storage like PCs. That is why - with the wrong wiring - it was forgetting all settings. OS and software is in ROM, no disk. If there was disk, CE could have written back to disk.

If you know the Configuration file used by the UI, you can set GPS or USB or something else as default. It all depends on whether you can connect the unit to a PC (laptop) and the unit appears as a disk-drive.
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Old 17th January 2013, 19:48   #3
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Default Re: Memory retention of tuning parameters & clock in a Head-Unit

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Originally Posted by DerAlte View Post
Wrong wiring. Wonder who did that wiring - even your Pio would have lost settings every time you switch off ignition. Yellow should be BAT, Red should be ACC (ignition switch). If both Yellow and Red are connected to ACC, there will be no power to the HU to retain any settings.

Don't worry about drain - 100mA draw is 1.2AH per hour. Your battery can sustain it for a day at least. ('Dirt cheap' - they don't expect you to complain of battery drain ). But, I also think 100mA is unusual, and this means that the CPU is not going to 'sleep'. With Ignition off, the consumption is expected to be <10mA.

Cost and maintainability:
* Unlike consumer equipment and PCs, it is impossible for User to open the cover and replace the coin cell
* NV-RAM / EEPROM is a costly piece of hardware - too high % cost of unit cost
All retention objectives are met with the mechanism of ACC - the hardware can go to low-power mode, since the battery is always connected.

That board must be using HU conventions, not computer conventions - and doesn't have non-volatile storage like PCs. That is why - with the wrong wiring - it was forgetting all settings. OS and software is in ROM, no disk. If there was disk, CE could have written back to disk.

If you know the Configuration file used by the UI, you can set GPS or USB or something else as default. It all depends on whether you can connect the unit to a PC (laptop) and the unit appears as a disk-drive.
I follow your logic but I must say that in the Pioneer, the electrician had indeed wired it correctly. However after my battery went flat on two occassions (that too within two months of my taking delivery of my new car) I decided to remove the Yellow wire from the battery and connected it to the Red (accepting the irritation of retuning the tuner on every power-up as the lesser evil). After this change I never had a flat battery which convinced me that it indeed was the problem. The fact is I sometimes don't use the car for 3 or 4 days at a stretch.
As for using the EEPROM, I have personally used a 1KB EEPROM in TV receivers (for storing tunning and control parameters for 100 channels) for just Rs 10/-. So I don't understand why it cannot be used in a HU which costs in tens of thousands.

There also could be innovative means of changing coin batteries in a HU if the need was really felt. The question is whether I am in a minority (one of my close friends too had the same problem in his Estilo with Sony HU which was solved by the same shifting of the yellow wire) as far as this "memory retention" is concerned. Maybe some others in this forum who have had a similar experience (of battery discharge due to the HU) can put forth their views.
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Old 18th January 2013, 12:20   #4
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Default Re: Memory retention of tuning parameters & clock in a Head-Unit

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Originally Posted by nitnab View Post
... I decided to remove the Yellow wire from the battery and connected it to the Red (accepting the irritation of retuning the tuner on every power-up as the lesser evil). ...
Oh, I thought the installer had shorted BAT and ACC. Anyhow, you should have looked into the battery drain issue instead of changing wires. There is something that is preventing the board from 'sleeping', even though the display is off. You are an electronics engineer, I am sure you will be able to debug the excess current draw problem.

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Originally Posted by nitnab View Post
... As for using the EEPROM, I have personally used a 1KB EEPROM in TV receivers (for storing tunning and control parameters for 100 channels) for just Rs 10/-. So I don't understand why it cannot be used in a HU which costs in tens of thousands. ...
The HU costs US$100-400; the manufacturing cost is significantly less (maybe 30-40% of that). The ratio to the manufacturing cost is different, and the manufacturer saves a lot by not providing it. The issue is not so simple as you put it.

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Originally Posted by nitnab View Post
... There also could be innovative means of changing coin batteries in a HU if the need was really felt. ...
ICE is a 'fit & forget' system. Not everyone is a capable hands-on person. But, obviously the need was never felt.

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Originally Posted by nitnab View Post
... The question is whether I am in a minority ...
It would seem so. Very few people have reported a problem of losing settings. And, other than people who put in SPL systems without changing battery, or people who used the ICE as an outdoor party music system with engine off, no one has complained of ICE draining their battery.
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Old 18th January 2013, 16:00   #5
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Default Re: Memory retention of tuning parameters & clock in a Head-Unit

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Originally Posted by DerAlte View Post
Oh, I thought the installer had shorted BAT and ACC. Anyhow, you should have looked into the battery drain issue instead of changing wires. There is something that is preventing the board from 'sleeping', even though the display is off. You are an electronics engineer, I am sure you will be able to debug the excess current draw problem.

The HU costs US$100-400; the manufacturing cost is significantly less (maybe 30-40% of that). The ratio to the manufacturing cost is different, and the manufacturer saves a lot by not providing it. The issue is not so simple as you put it.

ICE is a 'fit & forget' system. Not everyone is a capable hands-on person. But, obviously the need was never felt.

It would seem so. Very few people have reported a problem of losing settings. And, other than people who put in SPL systems without changing battery, or people who used the ICE as an outdoor party music system with engine off, no one has complained of ICE draining their battery.
I tend to think you are right about my being in a minority as far as this battery drain problem is considered (unless some others respond on this forum to the contrary). As for opening the unit to debug the high current drain in the present chinese unit, I am keeping my fingers crossed that the unit gives me atleast a few years of service without further endagering the chances of it's survival by opening it. Even the "hacking" to default to the GPS function will be attempted only if I am reasonably certain that I will not brick it.
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