Enum opentitanlib::io::gpio::BitbangEntry

pub enum BitbangEntry<'rd, 'wr> {
    Write(&'wr [u8]),
    WriteOwned(Box<[u8]>),
    Both(&'wr [u8], &'rd mut [u8]),
    BothOwned(Box<[u8]>),
    Delay(u32),
    Await {
        mask: u8,
        pattern: u8,
    },
}

Represents one entry in the specification of a bitbanging waveform. Pins must have been configured as either PushPull, OpenDrain or Input prior to requesting a bitbang operation.

Write and Both are somewhat equivalent to their namesakes in spi::Transfer, that is Write requests using the given data for generating waveforms on any of the pins configured as output, while disregarding the actual levels of the pins. Both requests generating a waveform, and also sampling every pin at each clock tick.

Variants

Write(&'wr [u8])

Represents a sequence of pin values. Bit 0 in each byte controls the first GpioPin in the slice given to GpioBitbanging::run(), bit 1 controls the second GpioPin, and so on. Each byte is applied to the pins in sequence, with a particular delay between each given by the clock_tick argument to run().

WriteOwned(Box<[u8]>)

Same as Write, but this BitbangEntry owns the data.

Both(&'wr [u8], &'rd mut [u8])

Represents a sequence of pin values as above, but additionally captures the value of any pins in Input or OpenDrain mode. At each clock tick, the input levels are sampled just before the given output levels are applied, meaning that the data coming back will be offset by one sample.

BothOwned(Box<[u8]>)

Same as Both, but this BitbangEntry owns the data, which will be overwritten.

Delay(u32)

Represents a delay of the given number of clock ticks in which the output levels are held as indicated by the last byte of the preceding Write/Both entry.

A delay of zero is invalid. A delay of one tick is equivalent to not specifying any Delay between two Write blocks, which is also equivalent to concatenating the two into a single Write block.

Await

Fields

mask: u8

pattern: u8

Similar to Delay, but waits until (pin_values ^ pattern) & mask equals zero, that is, until the set of pins indicated by ones in mask all have the the value indicated in pattern.