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Use modify instead of write for clearing sr1 #298

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Use modify instead of write for clearing sr1 #298

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d7c817f
Use modify instead of write for clearing sr1
TheZoq2 Dec 23, 2020
d805d28
Clear start bits before send
TheZoq2 Jan 23, 2021
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
- Fix > 2 byte i2c reads
- Send stop after acknowledge errors on i2c
- Fix i2c interactions after errors
- Only clear individual i2c status registers on error

### Changed
- Use `cortex-m-rtic` instead of `cortex-m-rtfm` in the examples
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8 changes: 4 additions & 4 deletions src/i2c.rs
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Expand Up @@ -220,16 +220,16 @@ macro_rules! wait_for_flag {
let sr1 = $i2c.sr1.read();

if sr1.berr().bit_is_set() {
$i2c.sr1.write(|w| w.berr().clear_bit());
$i2c.sr1.modify(|_r, w| w.berr().clear_bit());
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@burrbull burrbull Dec 26, 2020 •
edited
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Suggested change
$i2c.sr1.modify(|_r, w| w.berr().clear_bit());
$i2c.sr1.write(|w| w
.bits(0xffff)
.berr().clear_bit()
);

Something like this

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In theory, one should use an all-one mask instead of the previous register value, because the register value can be changed during the read-modify-write sequence and this code will end up clearing bits it wasn't supposed to clear.

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I agree
изображение

Err(Other(Error::Bus))
} else if sr1.arlo().bit_is_set() {
$i2c.sr1.write(|w| w.arlo().clear_bit());
$i2c.sr1.modify(|_r, w| w.arlo().clear_bit());
Err(Other(Error::Arbitration))
} else if sr1.af().bit_is_set() {
$i2c.sr1.write(|w| w.af().clear_bit());
$i2c.sr1.modify(|_r, w| w.af().clear_bit());
Err(Other(Error::Acknowledge))
} else if sr1.ovr().bit_is_set() {
$i2c.sr1.write(|w| w.ovr().clear_bit());
$i2c.sr1.modify(|_r, w| w.ovr().clear_bit());
Err(Other(Error::Overrun))
} else if sr1.$flag().bit_is_set() {
Ok(())
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