hwconf/*: disable DAC buffer to increase accuracy #755
+11
−11
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
According to the STM32F4 datasheet, the ADC is equipped with a buffer for being able to drive external loads directly. This buffer negatively impacts accuracy, though. The offset can be as high as 0.2V. Thus, disable the buffer by setting the BOFFx flag. This was verified on a STM32 nucleo64 F446RE by reading the DAC voltage back via ADC and comparing results with and without BOFFx=1. The output voltage was verified (calibrated DMM BM789) to be correct with BOFFx=1. Reference: STM DS8626 STM32F40xxx Rev 9 - 5.3.25 DAC electrical characteristics - Figure 53. 12-bit buffered non-buffered DAC Signed-off-by: Michael Niewöhner <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
According to the STM32F4 datasheet, the ADC is equipped with a buffer for being able to drive external loads directly. This buffer negatively impacts accuracy, though. The offset can be as high as 0.2V.
Thus, disable the buffer by setting the BOFFx flag.
This was verified on a STM32 nucleo64 F446RE by reading the DAC voltage back via ADC and comparing results with and without BOFFx=1. The output voltage was verified (calibrated DMM BM789) to be correct with BOFFx=1.
Reference:
STM DS8626 STM32F40xxx Rev 9