MP3 won't charge after PC was in sleep mode - Page 1
Forum section: electronics / general

author: MathWizard
author_rank: Super Contributor
timestamp: March 24, 2022, 03:32:03 pm
content: I had my MP3 player charging on my PC, and the PC went to sleep, so the 5V shuts off. It worked after, then the battery drained. Now the player won't stay in charging mode.Normally, when it's off, if you plug it into a charger or USB port, it will power up and start charging. Now if I plug it in, it does nothing. If I plug it in, then turn it on, it powers up for a moment, and the battery looks like it's charging, and my computer can see it, but then it shuts down again. I tried plugging it in, restarting the PC, and putting the PC into sleep-mode, no luck resetting the MP3 player to normal.There's no reset button, and I can't find a reset procedure anywhere online. So I'm guessing I just need to reset it. The MCU is an ATJ3315d, does anybody see a reset pin on this, I don't see a hardware reset mentioned ??https://datasheetspdf.com/pdf-file/774999/Actions/ATJ3315/1

author: eutectique
author_rank: Frequent Contributor
timestamp: March 24, 2022, 06:01:19 pm
content: What voltage do you measure on the battery terminals when the charger is connected? When disconnected?

author: tunk
author_rank: Super Contributor
timestamp: March 24, 2022, 06:16:10 pm
content: I'd guess the cell voltage is below 3, and that therefore the BMS or charging circuit will not charge it.

author: MathWizard
author_rank: Super Contributor
timestamp: March 25, 2022, 05:41:35 pm
content: It's 3.89V, not charging, I'm not used to Li cells, but so they don't let them run too empty, is that it ?. Turning it on now, it acts like it normally does when the battery is too low. Many MP3 players I've seen, have a rest button. There's no button inside this 1, and no option in the menu's either, and nothing in the manual.I wish I had the time to go figure out how to see the program inside this thing. And if there's no pin labeled reset on the MCU, I'd have to try pulling a few H/L, and that might do nothing.I would have a look at it on the scope, when I plug it in next time, but the MCU handles all the charging, so probably nothing to see. I have to get a wire soldered on.Maybe unhooking the battery for awhile might reset it too, worth a shot.I have another semi-working MP3 player for now at work, but I really better go get a new 1, or try an old cell phone I found, maybe it plays MP3s.

author: mikerj
author_rank: Super Contributor
timestamp: March 25, 2022, 06:38:27 pm
content: I recently repaired a car satnav that did something very similar, cell appeared to be fully charged but it would shutdown after a few tens of seconds when powered up. Turned out to be a fault battery protection circuit, the MOSFET pass transistor wasn't being switched fully on so added a bunch of extra resistance into the circuit.If you monitor the battery voltage after switching the MP3 player on, does the voltage remain stable at ~4v?

author: eutectique
author_rank: Frequent Contributor
timestamp: March 25, 2022, 07:24:56 pm
content: The voltage is reasonable. If the battery is soldered, you can short it for a moment to cause power-on reset.

author: MathWizard
author_rank: Super Contributor
timestamp: March 26, 2022, 02:52:05 am
content: Ok I'll have to make the time and solder on a few wires, some how that seems like quite the chore, the battery wires are glued down, and at any moment I'm at risk of breaking the USB flex cable on the charging plug, on the other 1/2 of the case.A while back I lost the headphone output on this thing, and I reasoned that it was related to an incident involving a wall charger, and the order of operations of doing that. And I plugged it back into my computer's USB port, and did something in some order, and was able to get the HP sound back again.I'm sure this time, the MCU thinks it's still supposed to charging, and when my PC's PSU went to sleep, it's bungled the MCU's logic, as it hit the lower limit of the "save the Li battery" voltage. And it just needs a reset.Maybe just flipping some ram bit, would tell the MCU things are ok, but yeah, much to learn about MCU's do I

author: MathWizard
author_rank: Super Contributor
timestamp: March 26, 2022, 11:14:08 pm
content: Hmm, I went to look at prices of MP3 players, and I recognized 1 of them...because I bought it ages ago, and was waiting for the last 1 to fail.I have a few broken, and semi-working MP3 players. So some have working MCU's, otthers have a working RAM chip. If I knew some more programing and how to use my BusPirate, to get the ROM's, I should be able to combine any MP3 capable MCU with a RAM chip. So I'm not throwing out the old ones yet, some day I WILL HACK together a new MP3 player.I want to make a stereo FM TX, fed from my PC, to a RX and little stereo, made from laptop speakers. And then I'll be able to listen to my PC from any room in the house. I should try and incorporate some of these old MP3 players into that too. 1 of the old MP3 players has a discrete FM radio chip, I want to try that approach someday too, but I really want to learn more about analog radio's. So far, I don't get how RLC circuits make the FM, but that's ok, because I guess I don't know all the math to deal with that either.

author: MathWizard
author_rank: Super Contributor
timestamp: April 07, 2022, 02:04:31 am
content: Well the new MP3 player I found in my drawer, I forgot, not only did it not have RAM, it did'n come with a SD chip, and it didn't even have a battery, I never thought to check when buying it. It can take a AAA battery, but so far I can not get it to turn on or do anything from battery. But when hooked to the PC, I can at least copy files to it. So IDK what kind of junk that is. I must probe that 1 too.My MP3 player I 1st posted about, I desoldered the battery, and left it for a while, and put it back, and it was still having problems charging. But it did take a charge from my bench PSU. I also broke the USB flex cable, and spliced that.Then it seemed to work as expected again, plugged into the PC. Then I tried that SD chip in this one, and something bad happened, IDK what....it was snapped in....at the time the battery had lots of charge left, but seemed to get shorted, and now it won't stay charging from the PC again. I'll try my w/ my PSU again, and this time put the scope on the charging area/pin......Then the one I'm using lately, it used to work years ago, then it's H/P had problems that I sort of fixed, but both L/R and L/R/Mic headphones, don't work right without being half pulled out. I don't get it. And I lost the main ring of buttons for it years ago.But it also has some serious problems, like loss of USB connection, in the middle of file transfers/etc. It's not corrosion. Windows will say it finds and fixes errors, but it doesn't really. It also seems to have a bad button bounce problem, or something worse in the MCU.Plus files that are 1 hour long might say they are 17min long. That's maybe some bitrate issue, old firmware, god only knows. And files that work, sometimes won't, after pausing, turning off and back. I have lot's of salvaged ram chips, if I knew it was just the ram chip problem, I might even have 1 here the same RAM size and footprint, so no re-programing needed.All that before I dropped it part way in the toilet the other day, but I washed it off and dried it, it's still "working" the same.So that's my main 1 for now, I don't want to mess with it yet, that's all I have for work. I could buy 1 right now, but I'm too cheap, and that's no fun.I have another MP3 player w/ 8GB which I miss, but it's headphone jack, or some trace or something, has a problem, I need to have a go at that 1. Right now it only wants to use it's speaker. Years ago I might have tried soldering the headphone jack, maybe I shorted underneath it. I should get the probes on that, not what follows below.So I have a mini-clip MP3 player I found abandoned, that doesn't seem to do anything, beside use 12mA from USB, and it won't do anything at all from it's battery wires, besides use 4mA on some pulldown resistor when the play button is pushed.The PC doesn't recog it. There is a little dotmatrix LCD, that looks intact, but I've never seen it working. It's LED never seemed bright at all, and then I ran 70mA through it by accident, but it never fried, not fully anyways. I never tried probing anything to see if the LCD is receiving info from the MCU.So I found a generic schematic for this MP3 player MCU, below, a BR3188 , 48pin. I see it has I2C, so I hooked up my Bus Pirate. But I don't know programing, or know what to do next..........all I want to do, is see if the MCU is running, or what...I have the pulldown resistors on, and I can turn on the 5V, and I can read an address, I'm not sure on the syntax for that really, but I've never had it read back anything besides zero's. Even if I got something, well then what.So far I can't find a datasheet for the BR3188, any idea's what it might be like ? I've seen the programming datasheets for MCU's, it's mostly Greek to me, but trying to look up any of this on google, is usually just as frustrating.

author: MathWizard
author_rank: Super Contributor
timestamp: April 07, 2022, 04:53:37 pm
content: I fixed the 8GB player with a touchscreen. Years ago I tried to replace it's TRS jack, and I must have knocked off a 0R jumper for the sleeve to GND. I probably never had flux back then, or Copper braid.I have the other good 1, recharging itself from 5V, if I had the data lines connected, it would not charge. So I'll probe it next. I have another MP3 player that I broke the nice big screen on. I just need to order 1 for that.But I have a bunch of junk with MCU's, I'm sure most of the chips can be removed, and there is probably some open-source programs for basic MP3 players. Way over my head yet tho to write my own. But If I could "dump the ROM" , I would.