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attenuators: use robust latching sequence

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To ensure that eatch call to latch() generates a rising edge, first
assert low, then high, not the other way round.
This commit is contained in:
Robert Jördens 2021-05-25 20:59:48 +00:00
parent a9f5943296
commit fc78b087ee
1 changed files with 8 additions and 11 deletions
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19
src/hardware/pounder/mod.rs
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@ -313,12 +313,7 @@ impl PounderDevices {
.map_err(|_| Error::I2c)?;
devices
.mcp23017
.write_gpio(mcp23017::Port::GPIOB, 1 << 5)
.map_err(|_| Error::I2c)?;
devices
.mcp23017
.digital_write(EXT_CLK_SEL_PIN, false)
.write_gpio(mcp23017::Port::GPIOB, 0x2F)
.map_err(|_| Error::I2c)?;
Ok(devices)
@ -351,23 +346,25 @@ impl AttenuatorInterface for PounderDevices {
Channel::Out0 => ATT_LE1_PIN,
Channel::Out1 => ATT_LE3_PIN,
};
self.mcp23017
.digital_write(pin, true)
.digital_write(pin, false)
.map_err(|_| Error::I2c)?;
self.mcp23017
.digital_write(pin, false)
.map_err(|_| Error::I2c)?;
// TODO: Measure the I2C transaction speed to the RST pin to ensure that the delay is
// sufficient. Document the delay here.
self.mcp23017
.digital_write(pin, false)
.digital_write(pin, true)
.map_err(|_| Error::I2c)?;
Ok(())
}
/// Read the raw attenuation codes stored in the attenuator shift registers.
///
/// Args:
/// * `channels` - A slice to store the channel readings into.
/// * `channels` - A 4 byte slice to be shifted into the
/// attenuators and to contain the data shifted out.
fn transfer_attenuators(
&mut self,
channels: &mut [u8; 4],