[2.0.x] Ensure ADC conversion is complete before reading#11336
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thinkyhead merged 1 commit intoMarlinFirmware:bugfix-2.0.xfrom Jul 26, 2018
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[2.0.x] Ensure ADC conversion is complete before reading#11336thinkyhead merged 1 commit intoMarlinFirmware:bugfix-2.0.xfrom
thinkyhead merged 1 commit intoMarlinFirmware:bugfix-2.0.xfrom
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@thinkyhead I have no idea why this pull request includes changes committed by you on the 25th June to the configuration files. Sorry about that. Do I need to revert them from my fork and then resubmit this? |
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Currently investigation a potential issue with this, please do not merge. |
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Latest changes have been tested and it looks pretty good. No glitches on hotend, or heated bed. Should be OK to merge I hope. |
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I can fix this up — just needs a rebase, as the source branch probably got rebased. |
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The current Marlin implementation makes relies on a timer interrupt to start the ADC conversion and read it. However in some circumstances the interrupt can be delayed resulting in insufficient time being availabe for the ADC conversion. This results in a bad reading and false temperature fluctuations. These changes make sure that the conversion is complete (by checking the ADC hardware via the HAL) before reading a value. See: MarlinFirmware#11323
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Description
This PR extends the HAL interface to allow code to check if the ADC conversion is complete and uses this to ensure correct temperature and other ADC based readings.
The current implementation relies on an interrupt timer to start the conversion and read the ADC value. However in some circumstances other interrupts can delay the start point which can result in the conversion not being complete by the time the ADC value is read. This PR checks to see if the conversion has been completed and if not it delays the read until the next timer interrupt.
Note: This PR only provides HAL implementations for AVR and LPC1768 variants, place holders are provided for other HALs and these may need to be modified (but without any change things are essentially as before).
Benefits
With the current implementation invalid temperature readings can be made in some circumstances (particularly on AVR based systems) resulting in fluctuations in the hotend (and to a lesser extent) bed temperature. This change provides a more consistent temperature.
Related Issues
See issue: #11323