cpu/sam0_common: fix DAC on SAM D5x/E5x #21548
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crasbe
reviewed
Jun 10, 2025
crasbe
approved these changes
Jun 11, 2025
Using the external reference produces no output when no voltage is connected, which makes for a confusing non-functional DAC on the eval board.
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Contribution description
When writing data too quickly on SAM E54, the DAC driver would hang on
while (DAC->SYNCBUSY.reg & mask) {}.The errata sheet suggests to check for
INTFLAG.EMPTYinstead when using internal reference, so just do that.Also use the internal voltage reference by default on
same54-xproto avoid seeing no output at all when using the external reference (and not connecting it to Vref, which is a pretty obscure thing to do).We only get a 1V amplitude, but that's still better than 0V.
Testing procedure
tests/drivers/dac_ddsproduces a neat sine wave for 2s withsine 440 2.Verified this both on
same54-xproandsamd21-xproto avoid introducing a regression there.Issues/PRs references