Eth PHY reset time might not be long enough #141
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This was referenced Sep 16, 2020
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144: Fix syntax for taking core peripherals (required by cortex-m-rtic v0.5.5) r=jordens a=HarryMakes This is to fix a panicking upon initialization problem that is caused by a now undefined behaviour in our code from the perspective of the latest release of the cortex-m-rtic crate. As per conversation in rtic-rs/rtic#361, `context.core` should now be used instead of `cortex_m::Peripherals::take()`, which would cause some unexpected behaviour. On a side note, a similar symptom where the Ethernet PHY does not get reset, as discussed in #141, might have also arisen from this new version of rtic. However, the reset delay still seems a bit too short to me. Co-authored-by: Harry Ho <[email protected]>
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t_RSTIA is 100 µs.
But arguably there should be sufficient delay between power supply ramp up and that reset. The setup before that may not take long enough. |
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Changing it in software doesn't appear to alter behavior. Changing it in hardware is sinara-hw/Stabilizer#84 |
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When powering the board with 12V, the Ethernet PHY LAN8742A won't have enough time to reset sometimes. If the reset is done and long enough, the two LEDs on the RJ45 plug should blink briefly upon power-cycling the board - this can't be observed when the PHY hasn't been reset properly.
A solution is to lengthen the deassertion of the nRST signal to 25ms by replacing this line in src/main.rs. According to the PHY's datasheet, this should be sufficient for the duration of "external power supplies at operational level to nRST deassertion".
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