Lines Matching +full:low +full:- +full:level

16   - The descriptor-based interface is the preferred way to manipulate GPIOs,
17     and is described by all the files in this directory excepted gpio-legacy.txt.
18   - The legacy integer-based interface which is considered deprecated (but still
19     usable for compatibility reasons) is documented in gpio-legacy.txt.
21 The remainder of this document applies to the new descriptor-based interface.
22 gpio-legacy.txt contains the same information applied to the legacy
23 integer-based interface.
29 A "General Purpose Input/Output" (GPIO) is a flexible software-controlled
37 System-on-Chip (SOC) processors heavily rely on GPIOs. In some cases, every
38 non-dedicated pin can be configured as a GPIO; and most chips have at least
43 Most PC southbridges have a few dozen GPIO-capable pins (with only the BIOS
48   - Output values are writable (high=1, low=0). Some chips also have
50     value might be driven, supporting "wire-OR" and similar schemes for the
53   - Input values are likewise readable (1, 0). Some chips support readback
54     of pins configured as "output", which is very useful in such "wire-OR"
56     input de-glitch/debounce logic, sometimes with software controls.
58   - Inputs can often be used as IRQ signals, often edge triggered but
59     sometimes level triggered. Such IRQs may be configurable as system
60     wakeup events, to wake the system from a low power state.
62   - Usually a GPIO will be configurable as either input or output, as needed
65   - Most GPIOs can be accessed while holding spinlocks, but those accessed
69 MMC/SD card insertion/removal, detecting card write-protect status, driving
70 a LED, configuring a transceiver, bit-banging a serial bus, poking a hardware
81 Active-High and Active-Low
82 --------------------------
84 ("high"), and inactive when it is 0 ("low"). However in practice the signal of a
88 being either active-high ("1" means "active", the default) or active-low ("0"
90 not about what happens at the line level.
93 --------------------------
94 Sometimes shared signals need to use "open drain" (where only the low signal
95 level is actually driven), or "open source" (where only the high signal level is
97 used for TTL. A pullup or pulldown resistor causes the high or low signal level.
98 This is sometimes called a "wire-AND"; or more practically, from the negative
99 logic (low=true) perspective this is a "wire-OR".
101 One common example of an open drain signal is a shared active-low IRQ line.
109  LOW:	gpiod_direction_output(gpio, 0) ... this drives the signal and overrides
116 high signal and configuring the GPIO as input for low. This open drain/open
119 If you are "driving" the signal high but gpiod_get_value(gpio) reports a low
121 driving the shared signal low. That's not necessarily an error. As one common