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tests/periph/selftest_shield: re-enable ADC test

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The R-2R resistor ladder dac --> ADC test was disabled due to a bug in
the v0.1 version of the shield. Since this has been fixed in v0.2 and
v0.3 of the shield, it can be re-enabled.

The comment regarding the high accuracy of the resistor is dropped, as
v0.3 has been ordered with cost efficient resistors rather than with
accurate ones. As a result, the tolerance for error has been increased
to 10%. This quite a bit more lax than I have hoped for, but false
positives would be something to avoid.
This commit is contained in:
Marian Buschsieweke 2023-11-13 16:11:22 +01:00
parent 47d81ffbe1
commit f51ca593ba
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GPG Key ID: 77AA882EC78084E6
1 changed files with 5 additions and 6 deletions
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11
tests/periph/selftest_shield/main.c
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@ -93,10 +93,9 @@
* - periph_adc support (so that we have something to test)
* - Arduino I/O mapping for ADC (so that we know which line to test)
* - The PCF857x driver (so that we can control the R-2R resistor ladder
* connected to the GPIO expander.
* connected to the GPIO expander).
*/
#if defined(MODULE_PERIPH_ADC) && defined(ARDUINO_A0) && defined(MODULE_PCF857X) && 0
// TODO: Re-anble when PCB is fixed
#if defined(MODULE_PERIPH_ADC) && defined(ARDUINO_A0) && defined(MODULE_PCF857X)
# define ENABLE_ADC_TEST 1
#else
# define ENABLE_ADC_TEST 0
@ -979,9 +978,9 @@ static bool periph_adc_test(void)
uint16_t sample = adc_sample(ARDUINO_A0, ADC_RES_10BIT);
uint16_t expected = i << 6;
/* the resistors are said to be rather accurate, so lets be a bit
* more strict here */
const uint16_t delta = 16;
/* The resistors on board v0.3 are not that accurate, so allow for 10%
* error margin */
const uint16_t delta = 1024 / 10;
uint16_t lower = expected <= delta ? 0 : expected - delta;
uint16_t upper = MIN(1023, expected + delta);
bool test_failed = TEST((lower <= sample) && (upper >= sample));