VonK :: Retired

:-/ I stand corrected. How do flash and SRAM differ?

AxelS4

SRAM - static random access memory - typically is a 6 T(ransistor) cell, and very fast. However, it is the opposite of non-volatile. Power off, contents gone. Flash is a 2T cell usually, though there are some 1T and even 1/2 T (one cell maintains four different voltage levels and therefore two bit per cell) architectures. Very slow, and keeps its contents for extended periods of time, even with no power supplied into the chip. SRAM with access times sub 1 ns are available, and zero bus turnaround SRAMs allow for extremely high data rates. Flash (typically) is even slower than DRAM.

AxelS4

the voltmeter in the dash is a totally stupid design. It does not show the voltage go down if the battery is weak because all it does is use a slow Successive Approximation Register ADC that by design cannot track slow decreases in voltage, it can only catch spikes. If your battery is at 8 V and it got there slowly (because it died), then your in-dash voltmeter will show still somewhere between 12 and 14 Volt. You will need a real voltmeter or DVM to check. Audi COULD have used a voltage regulator (Zener Diode) to get the supply and the reference voltage down to 2 V, and then compare the battery voltage over a voltage divider to this. Would have cost a few more pennies.

RS_F-Whore

... turns out my factory alarm kept tripping and I would need to effectively unlock the car twice (using the remote - once to unlock the car, the second time to reset the immobiliser). Same symptoms - no ECL light, will turn over, but won't start.

Not sure if you have the Euro alarm/immobiliser in the US, but I thought I'd share my experience.

VonK :: Retired

Thanks, Axel.

VonK :: Retired

What else is it good for?

WECoyote-SuperGenius

turn ignition on, all idiot lights working including epc & c/e lights.
car starts right up
no access to APR programs, except being able to set anti-theft feature.
set anti-theft, shut car off, turn ignition on, disable anti-theft, start car, able to access programs.
drive to work, remove ecu, spray radio shack contact/control cleaner&lubricant on ecu pins and both end plugs of ecu harness. gently blow off excess, let dry, reinstall.
do tb alignment, start car, still no access to programs, set anti-theft, shut car off, disarm anti-theft, start car, gain access to programs.
shut car off, re-start, have access to programs, shut car off.
wait and see what happens this evening.
spoke to audi tech last night (has side business working on modded and out of warranty cars on weekends)
he will vag car saturday and check charging system, but he really believes the issue is the ecu itself, not with APR's chip or program. his opinion is that since i have no issues (no instances of not getting epc & c/e lights) when using the ecu that came with the car (stock/factory), it has nothing to do with the charging system.
i just recalled that the evening before my troubles began, the factory alarm went off for no apparant reason about 5 minutes after i locked the car up. Related to my problems?
will also replace turn signal / cruise control stalk this saturday, for sh*ts and giggles. (maybe that's screwing things up)

AxelS4

the voltmeter needs its power supply from somewhere, and a reference. Since they did not want to put in another battery, they tied VCC and VREF to battery through a big capacitor. So if the voltage on the battery drops quickly, the cap holds its charge and voltage, and you will see the reading go down. However, if the voltage goes down slowly, the capacitor charge goes down at the pretty much same rate, and so you compare VBatt to VREF, which are identical. Ergo your reading is 12 to 14 volts... Stupid, really stupid.

AxelS4

more importantly, you can do all this in software (= no additional hardware except for the capacitor). A voltage divider and constanter (Zener Diode) and a real ADC would have cost another $2 including PCB space and engineering cost and whatever other stuff.

NYC_S

Thanks. email me at zhiggy513@hotmail.com.