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Merge pull request #102 from apgoetz/i2c-improvements
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Made improvements to polling i2c driver
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@hannobraun
hannobraun authored May 27, 2020
2 parents f9388c3 + b9018f2 commit 995e1b2
Showing 1 changed file with 84 additions and 45 deletions.
129 changes: 84 additions & 45 deletions src/i2c.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ use crate::dma::{
use crate::pac::{
i2c1::{
RegisterBlock,
cr2::RD_WRN_A,
cr2::{RD_WRN_A, AUTOEND_A},
}
};
use crate::rcc::Rcc;
Expand Down Expand Up @@ -181,8 +181,23 @@ where
pub fn release(self) -> (I, SDA, SCL) {
(self.i2c, self.sda, self.scl)
}

fn start_transfer(&mut self, addr: u8, len: usize, direction: RD_WRN_A) {

fn check_errors(&self) -> Result<(),Error> {
let isr = self.i2c.isr.read();
if isr.berr().bit_is_set() {
self.i2c.icr.write(|w| w.berrcf().set_bit());
return Err(Error::BusError);
} else if isr.arlo().bit_is_set() {
self.i2c.icr.write(|w| w.arlocf().set_bit());
return Err(Error::ArbitrationLost);
} else if isr.nackf().bit_is_set() {
self.i2c.icr.write(|w| w.nackcf().set_bit());
return Err(Error::Nack);
}
return Ok(());
}

fn start_transfer(&mut self, addr: u8, len: usize, direction: RD_WRN_A, autoend : AUTOEND_A) {
self.i2c.cr2.write(|w|
w
// Start transfer
Expand All @@ -193,37 +208,29 @@ where
.sadd().bits((addr << 1) as u16)
// Set transfer direction
.rd_wrn().variant(direction)
// End transfer once all bytes have been written
.autoend().set_bit()
// should we end the transfer automatically?
.autoend().variant(autoend)
);
}

fn send_byte(&self, byte: u8) -> Result<(), Error> {
// Wait until we're ready for sending
while self.i2c.isr.read().txe().bit_is_clear() {}
while self.i2c.isr.read().txe().bit_is_clear() {
self.check_errors()?;
}

// Push out a byte of data
self.i2c.txdr.write(|w| w.txdata().bits(byte));

// Wait until byte is transferred
loop {
let isr = self.i2c.isr.read();
if isr.berr().bit_is_set() {
self.i2c.icr.write(|w| w.berrcf().set_bit());
return Err(Error::BusError);
} else if isr.arlo().bit_is_set() {
self.i2c.icr.write(|w| w.arlocf().set_bit());
return Err(Error::ArbitrationLost);
} else if isr.nackf().bit_is_set() {
self.i2c.icr.write(|w| w.nackcf().set_bit());
return Err(Error::Nack);
}
return Ok(());
}
// check for any errors
return self.check_errors();

}

fn recv_byte(&self) -> Result<u8, Error> {
while self.i2c.isr.read().rxne().bit_is_clear() {}
while self.i2c.isr.read().rxne().bit_is_clear() {
self.check_errors()?;
}

let value = self.i2c.rxdr.read().rxdata().bits();
Ok(value)
Expand Down Expand Up @@ -263,7 +270,7 @@ where
Buffer::Target: AsSlice<Element=u8>,
{
assert!(buffer.len() >= num_words);
self.start_transfer(address, buffer.as_slice().len(), RD_WRN_A::WRITE);
self.start_transfer(address, buffer.as_slice().len(), RD_WRN_A::WRITE, AUTOEND_A::AUTOMATIC);

// This token represents the transmission capability of I2C and this is
// what the `dma::Target` trait is implemented for. It can't be
Expand Down Expand Up @@ -337,7 +344,7 @@ where
Buffer::Target: AsMutSlice<Element=u8>,
{
assert!(buffer.len() >= num_words);
self.start_transfer(address, buffer.as_slice().len(), RD_WRN_A::READ);
self.start_transfer(address, buffer.as_slice().len(), RD_WRN_A::READ, AUTOEND_A::AUTOMATIC);

// See explanation of tokens in `write_all`.
let token = Rx(PhantomData);
Expand Down Expand Up @@ -376,9 +383,58 @@ where
type Error = Error;

fn write_read(&mut self, addr: u8, bytes: &[u8], buffer: &mut [u8]) -> Result<(), Self::Error> {
self.write(addr, bytes)?;
self.read(addr, buffer)?;

let writing = bytes.len() > 0;
let reading = buffer.len() > 0;

// wait for i2c device to be available
while self.i2c.isr.read().busy().is_busy() {
self.check_errors()?;
}

// if we are writing bytes
if writing {

// if the previous write has failed, we need to flush the TX
// buffer to prevent sending old data
self.i2c.isr.write(|w| w.txe().set_bit());

if reading {
self.start_transfer(addr, bytes.len(), RD_WRN_A::WRITE, AUTOEND_A::SOFTWARE);
} else {
self.start_transfer(addr, bytes.len(), RD_WRN_A::WRITE, AUTOEND_A::AUTOMATIC);
}

// Send bytes
for c in bytes {
self.send_byte(*c)?;
}

// if we are going to read afterwards, we need to wait for
// the tx to complete
if reading {
while self.i2c.isr.read().tc().is_not_complete() {
self.check_errors()?;
}
}
}

if reading {

// force a read of the rx data register, so that we dont
// get stale data from the last transaction (if there is
// anything left over)
self.i2c.rxdr.read();

//send a new start condition and transfer
self.start_transfer(addr, buffer.len(), RD_WRN_A::READ, AUTOEND_A::AUTOMATIC);

// Receive bytes into buffer
for c in buffer {
*c = self.recv_byte()?;
}
}

Ok(())
}
}
Expand All @@ -390,16 +446,7 @@ where
type Error = Error;

fn write(&mut self, addr: u8, bytes: &[u8]) -> Result<(), Self::Error> {
while self.i2c.isr.read().busy().is_busy() {}

self.start_transfer(addr, bytes.len(), RD_WRN_A::WRITE);

// Send bytes
for c in bytes {
self.send_byte(*c)?;
}

Ok(())
self.write_read(addr, bytes, &mut [])
}
}

Expand All @@ -410,15 +457,7 @@ where
type Error = Error;

fn read(&mut self, addr: u8, buffer: &mut [u8]) -> Result<(), Self::Error> {
while self.i2c.isr.read().busy().is_busy() {}

self.start_transfer(addr, buffer.len(), RD_WRN_A::READ);

// Receive bytes into buffer
for c in buffer {
*c = self.recv_byte()?;
}
Ok(())
self.write_read(addr, &[], buffer)
}
}

Expand Down

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