Take the 2-minute tour ×
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It's 100% free, no registration required.

this is a bit of a long shot but I'm hoping someone has access to the full data sheet for one of the chips listed in the title, and can tell me what combination of VBUS_IN and resistors on ID_CON will make it trigger the BOOT pin on the chip. Unfortunately Fairchild will not release the full data sheet for these chips (I have asked), and only an abbreviated version (PDF link) is available on the web.

Long story: the FSA9480 chip is used on some Samsung phones to detect various accessories using sensing resistors on the ID pin of the USB port. We've already made a lot of progress through info from the phone's Android kernel source. Now we're trying to force the phone's CPU into a boot recovery mode that will make it load an external bootloader from the serial port, and it looks like the BOOT pin on the FSA9480 might do this, but we can't figure out how to trigger it.

So far I've tried all the resistors on the known list without power connected to the USB port, and all of the resistor values that produced serial output again with power on the USB port.

Update: We're working on the theory that this schematic from the service manual shows a signal going from the FSA9480 BOOT pin to a signal named BOOT_MODE, which in any sane world would go the the application processor chip's OM5 pin. But we don't have the full schematic to prove it, and we don't have the internal details of the FSA9480 to show how that pin gets triggered. You would think it would be the resistors with BOOT_ON in their names (like RID_FM_BOOT_ON_UART), but apparently not. Or maybe it is, but the BOOT_MODE signal doesn't go to the right place. Either way the FSAx80 data sheet would confirm it.

I've reverse-engineered the startup and bootloader download code in the application processor's (Samsung S5PC110) internal ROM, and worked out that if we succeed we should see the first byte of the bootloader download protocol on the serial port. Instead we are getting the output of the primary bootloader which is being loaded from NAND, which indicates a normal boot.

share|improve this question
1  
Post the links with spaces in them and we'll fix it for you –  endolith Apr 14 '11 at 14:39
1  
Two questions: How will you know you've succeeded? And also, from the datasheet it looks like the BOOT pin is connected to the baseband processor. My understanding is that this chip handles the cellular radio - not the higher functions - and that playing with it is a serious no-no as far as the FCC is concerned. What is your understanding of the connection of the BOOT pin? –  AngryEE Apr 14 '11 at 16:08
2  
Good updates, but in the future mark them so we know there was an update. Question the third: are you willing to crack open one of these phones and check traces to see if the signal goes to the right place? Also, question the fourth: what is the application processor? I'd like to find a datasheet. –  AngryEE Apr 14 '11 at 20:41
2  
Have you tried booting the phone, watching dmesg and changing the resistor values? I would try to setup a continually variable resister over the ranged needed and slowly change its value. I would expect the driver to dump mode information into dmesg. –  Mark Apr 14 '11 at 23:31
1  
@Mark thanks, unfortunately it only seems to register resistance changes if you unplug then reconnect the plug. I have tried the slow and painful way of setting a resistor to each value in the list. –  TheBeano Apr 15 '11 at 12:30
show 9 more comments

2 Answers

check out http://forum.xda-developers.com/showthread.php?t=1206216 I have done this to my captivate and it works. I do not know about any other Galaxy S phones. You should check xda-dev for your phone as someone may have figured out how to do it on it.

share|improve this answer
    
A link on its own is not considered an answer, please post the information here and add a link as a reference. –  Kortuk Apr 13 '12 at 1:57
add comment

Good morning, here you will find documentation

FSA9280

share|improve this answer
2  
That's only a 5 page 'limited datasheet', although it does contain an e-mail address to request the full datasheet that may help the OP if they haven't already tried to do that. Although if it's not posted online it may well require an NDA and/or only be available to OEMs. –  PeterJ Mar 8 '13 at 10:14
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.