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fw/boot/boot.c (boot_loader): removed description of IDBG-specific power

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sensing.
This commit is contained in:
Werner Almesberger 2010-08-19 09:03:34 -03:00
parent efdacaf589
commit 97d2ed102e
1 changed files with 0 additions and 24 deletions
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fw/boot/boot.c
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@ -186,30 +186,6 @@ static void boot_loader(void)
printk("%s #%u\n", build_date, build_number);
/*
* Very weakly pull SDA down and disable all pull-ups.
*
* We use SDA as a system power presence detector. When I2C is idle,
* SDA is kept high. This is accomplished with pull-ups in the system.
* We can therefore detect if IO_3V3 is any good by checking whether
* SDA is high.
*
* This should work even without our own pull-down. However, when the
* IDBG board is operating standalone (or, generally, if SDA isn't
* connected), SDA would float. We therefore have to pull it down a
* little.
*/
/*
* Ben variant:
*
* We use exactly the same logic as on GTA01/02, but with different
* signals. P0_1 (I2C_SDA_PULL) and P0_2 (I2C_SDA) both connect to
* +V3.3, with a 1 kOhm resistor on P0_1. If the Ben is not powered, we
* can therefore pull +V3.3 to GND, and detect this condition. As on
* the GTA01/02, once the system is powered up, IDBG exits this loop.
*/
PLATFORM_SETUP;
dfu_init();