1. OCAU Merchandise now available! Check out our 20th Anniversary Mugs, Classic Logo Shirts and much more! Discussion here.
    Dismiss Notice

Need help with resetting microcomputer chip

Discussion in 'Electronics & Electrics' started by Dodge M4S, Apr 1, 2020.

  1. Dodge M4S

    Dodge M4S Member

    Joined:
    Jul 31, 2006
    Messages:
    3,305
    Location:
    6061
    Hey guys, long story short, I bought a second hand head unit for my car as a spare so I can mod it (Id rather not attempt it on mine) but the problem is, I dont have the pin code for it. It uses a 4 digit pin code, and only numbers 1 to 6 are used (so only 360 combinations). My plan was to just hook it up and just smash through the combinations until I find the right one but after for failed attempts, the head unit locks me out for an hour. I opened the head unit up and its got an m30622mca-8m9fp chip in it. I googled for the datasheet, and I noticed its got a reset pin on it. Im reading about how to reset it, but I really dont understand what its saying. Is it saying that I need to connect the reset pin to 0.2V for a certain amount of time and its done? :confused: would resetting it mean it resets the the 1 hour lock?

    90348402_10157451031450749_4165404874462199808_o.jpg
     
    Last edited: Apr 1, 2020
  2. dirtyd

    dirtyd Member

    Joined:
    Jan 4, 2006
    Messages:
    4,041
    Location:
    Melbs
    Short answer, without knowing anything else about the surrounding circuitry, it will probably reset the 1 hour lock. The reset pin is active low, so it's activated with a logic low. That 0.2V is the highest voltage that it will register as a reset, so short the pin to ground and you should be right.
     
    Dodge M4S likes this.
  3. merlin13

    merlin13 Member

    Joined:
    Apr 12, 2003
    Messages:
    2,013
    Location:
    back in BrizVegas
    Without seeing the full data sheet and the surrounding circuitry I'd be going "Hmmmm, maybe...".

    I'd be curious/dubious that fiddling the Reset pin would simply reset the stored count-down timer - I'd suspect it'd simply result in "Have you turned it off then on again?", where the stored timer value is then compared to any RTC value from either embedded or a separate dedicated clock chip.

    If an hour hasn't passed then you'll still be twiddling your thumbs.

    But there's always the Suck It And See approach. Let us know if it works... :)
     
    Dodge M4S likes this.
  4. OP
    OP
    Dodge M4S

    Dodge M4S Member

    Joined:
    Jul 31, 2006
    Messages:
    3,305
    Location:
    6061
    Wow, thanks :):thumbup:. Ill give it a go. It's going to be a bit difficult because I'm not the best at soldering. I tried removing power hoping it will remove the 1 hour block, but it didn't. I was also hoping it would reset the counter, but still didn't :(
     
  5. mtma

    mtma Member

    Joined:
    Aug 12, 2009
    Messages:
    5,437
    Yeah the lock-out is probably flagged into non-volatile memory when it trips.

    What the micro controller's reset pin does is pretty much what a reset button does on a PC. It doesn't cause any wiping of data except for RAM*.

    *Some micro-controllers have a self-destruct mechanism if you access them via a programmer and fail an authentication routine enough times. But you don't want a bricked radio so don't do that !
     
    Dodge M4S likes this.
  6. aXis

    aXis Member

    Joined:
    Jun 27, 2001
    Messages:
    5,548
    Location:
    Kalgoorlie, WA
    If the programmers have been lazy, you might be able to try the code 3 times and then reset/power cycle it.
     
    Dodge M4S likes this.
  7. cvidler

    cvidler Member

    Joined:
    Jun 29, 2001
    Messages:
    13,525
    Location:
    Canberra
    Typically a reset pin on an IC is held low during the power on phase, until the power supply is stable, so the IC doesn't try to start/run with potentially unstable power that can cause errors.

    it's not what the OP is looking for.


    Have you considered going to the dealer (assuming its an OEM radio), and asking for the code? they might do it for free or a few bucks.
    some radios you need to original cars VIN for the lookup to work, so just the serial# on the radio itself.
     
    Dodge M4S likes this.
  8. merlin13

    merlin13 Member

    Joined:
    Apr 12, 2003
    Messages:
    2,013
    Location:
    back in BrizVegas
    Heh - wandered into a dealer with a workmate who needed to do that after she'd left the lights on a drained the battery dead, dead flat.

    Name Brand Australian made car, they wanted $90 for it... AND to see the car for themselves. :rolleyes:

    They got somewhat peeved when I guffawed and said "Sorry, HOW much? She only needs the code, not a new bloody radio. C'mon, Love. Ryda is just down the road, I'll buy you a better one for your birthday...".
     
    Dodge M4S likes this.
  9. cvidler

    cvidler Member

    Joined:
    Jun 29, 2001
    Messages:
    13,525
    Location:
    Canberra
    yeah, and some places earn the name "stealership".
     
    Dodge M4S likes this.
  10. OP
    OP
    Dodge M4S

    Dodge M4S Member

    Joined:
    Jul 31, 2006
    Messages:
    3,305
    Location:
    6061
    I gave Holden a call and they told me that I need the VIN of the car it came out of and they will give me the code for free, but guy I bought the head unit off doesn't have it.
     
  11. OP
    OP
    Dodge M4S

    Dodge M4S Member

    Joined:
    Jul 31, 2006
    Messages:
    3,305
    Location:
    6061
    Well, this is strange. I hooked it up again and it's still giving me the "lock out 1hr" error even though it's been a few days. I couldn't solder the wire because I'm hopeless :o but I am dodgy so I done this :lol:. It's making contact, but the thing is that when I connect the wire to ground, the deck seems to just turn off, then turn back on but still locked out :(. Strange. Might need to do some more reading.

    IMG_20200403_095722.jpg
    IMG_20200403_095812.jpg
     
  12. cvidler

    cvidler Member

    Joined:
    Jun 29, 2001
    Messages:
    13,525
    Location:
    Canberra
    as covered above the reset pin won't help you.

    you'll need to find the memory chip and read that out, decode what the data is, make a change, then write it back.
    not impossible, but without the doco, close enough to being so.
     
  13. cvidler

    cvidler Member

    Joined:
    Jun 29, 2001
    Messages:
    13,525
    Location:
    Canberra
    second thought, there may be a jtag and/or uart port on there to give you console access. really depends how complex the thing is and if there's any programmability in it, or if it's just all ROM.
     
  14. merlin13

    merlin13 Member

    Joined:
    Apr 12, 2003
    Messages:
    2,013
    Location:
    back in BrizVegas
    Funny that... well, I'm finding that funny. Anyone else?..

    Anyway, back in the Good Olde Days the last 4 digits of the radio's serial number sometimes worked... sometimes...

    Else methinks you're rather well screwed there. So methinks you've got two sane options:

    - write down every number set you try and just keep plodding along four attempts at a time, one of the combinations should work. Should... (360 divided by 4, times the day of the week, plus sleeps, times hours watching NetFlix... told you I thought it was funny...);

    - or Return To Sender and buy one that actually works. Wreckers are still open I believe...

    And with the code for the one already in your car? Dig it out of the Owner's Manual and write it down on the back of the radio.
     
  15. mtma

    mtma Member

    Joined:
    Aug 12, 2009
    Messages:
    5,437
    I was thinking about the serial number one last night... if you haven't tried that you should.
    In one possible variation, the timer starts counting when it reads the 'locked' flag out of its non volatile memory. In this case you need to keep it powered as if it was in the car in order for it to process an unlock.

    Also does it have an external RTC? Could inject a much higher count frequency to speed up time :lol:

    Although it might have a watchdog to lock out if that happens. Depends on how anal the designers were.
     
    Last edited: Apr 3, 2020
  16. dakiller

    dakiller (Oscillating & Impeding)

    Joined:
    Jun 27, 2001
    Messages:
    8,113
    Location:
    3844
    That reset pin is like the reset button on your PC, it just restart the system again, it doesn't stop windows saying your license is invalid.
     

Share This Page

Advertisement: