Sansa c250, want to save the LCD & button light on USB charging

[maltose]

Hi rockbox users and experts,

It is quite a stupid design for the OF of Sansa c250 that the LCD backlit and button light are always on during charging through the USB port on a PC. I am really afraid that this long-term illumination would shorten the lives of the LCD and the botton LED(s). Is there any way to prevent it? I currently do not have a travel charger for the c250, so charging though PC USB is the only way for me.

Also, I have found that for Rockbox version r16212, it is possible to charge the battery through the USB port when the Rockbox is running, without triggering the system to roll back to the OF. By this way, the lights will shut off after a few seconds. However, for the later versions (e.g., r16448), this feature seems no longer existent. Every time I plug the c250 into the PC USB port, the OF turns on, overriding the Rocbox, and then the lighting lasts forever until the player gets unplugged.

If anyone has got any idea about this, I would be more than grateful. Thank you guys in advance.

mal

[AlexP]

I wouldn't worry too much.  Modern blue LEDs have a lifetime of upwards of 50,000 hours, which equates to nearly 6 years of constant use.

[pixelma]

Also, I have found that for Rockbox version r16212, it is possible to charge the battery through the USB port when the Rockbox is running, without triggering the system to roll back to the OF. By this way, the lights will shut off after a few seconds. However, for the later versions (e.g., r16448), this feature seems no longer existent. Every time I plug the c250 into the PC USB port, the OF turns on, overriding the Rocbox, and then the lighting lasts forever until the player gets unplugged.

This behaviour is by no means a feature that got removed - it's actually a bug with the automatic reboot into the original firmware which it should do but which doesn't work correctly in all builds. It could behave the same way again in the next build you try or the one after... but I don't think Rockbox is charging the device at all during this time.

You can try charging in Rockbox by holding "select" while you insert the cable, this will get the c200 into charging mode. Personally I don't trust it yet (because my c200 reports a wrong battery voltage when connected this way) and prefer charging in the original firmware, and I also agree with BigBambi here. Possibly better charging support will come with the progress in the Rockbox USB driver.

[Strife89]

An interesting find:

If I plug my Sansa in while it is turned off and has a micro SD card inserted, it boots into the OF (which it should ). However, if the micro SD card is there, the Sansa does not connect to the PC. Instead (after the long "Refreshing Database" message), the Sansa sits there like it's not plugged in. Unplugging and plugging back in the USB cable causes it to start charging, but it still does not connect "properly"; that is, as a mass storage device. As a result, the lights turn off normally, and it charges.

Booting into the OF first, then letting the database refresh, then plugging it in, allows it to connect normally. Booting either way without the micro SD card allows it to connect nomally (I can insert the card after connection).

So, if the light show still bothers you, buy a micro SD card and plug it in.

[maltose]

Thank you, BigBambi, now I've got to know the lifetime of the blue LED used on the c250. However, is the long-term illumination harmful to the LCD? In my commonsense (probably not correct), LCDs are quite vulnerable. And thank you for the quick response (I just noticed the time you posted your reply).

Thank you,  pixelma, thank you for both of your responses, for this thread and another. Yes, your approach works quite well. Now I have the lastest build (r16460) but the Rockbox system stays during charging if the "select" botton is held during the cable insertion. It is a good idea (maybe only for me).

Thank you, Strife89. I also tried your method, yes, it works well, too (I have a 2G micro-SD card).

 

[Llorean]

Why would LCD's be vulnerable? Phones, laptop computers, desktop computers, and TVs are all manufactured out of LCDs that last many thousands of user hours.

[Strife89]

But wouldn't the heat generated by both lights being constantly on affect the battery a bit?

[gnu]

Heat is not good for LION batteries, but the lcd & LEDs generate almost no heat at all.

[Llorean]

The CPU being in use is probably going to generate far more heat than the LCD and LEDs.

[Strife89]

It was just a thought. My Sansa always feels pretty warm if I leave it connected (lights on) for 2 or 3 hours.

[zajacattack]

That's because of the flow of the electrons from the plug to the battery and the charging.

On a side note: Why not turn the LCD? Every little bit of battery power saved lowers time 'til another charge is needed which increases the battery's life, right?

[Strife89]

Yep. I usually use my "wall wart" to charge, which lets the screen stay off.

I can't wait until I can charge from Rockbox itself.