Difference between revisions of "TiLDA MK3/adc"
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(Created page with "See here [https://micropython.org/doc/module/pyb/ADC] for the main micropython documentation. All ADC readings are referenced to the supply rail, which is about 3.3V. To incr...") |
(fix broken link to micropython adc docs) |
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| − | See here [https://micropython.org/ | + | See here [https://docs.micropython.org/en/latest/pyboard/library/pyb.ADC.html] for the main micropython documentation. |
All ADC readings are referenced to the supply rail, which is about 3.3V. To increase the ADC accuracy, the internal voltage reference can be read, and used to offset variations in the supply rail. | All ADC readings are referenced to the supply rail, which is about 3.3V. To increase the ADC accuracy, the internal voltage reference can be read, and used to offset variations in the supply rail. | ||
| Line 6: | Line 6: | ||
adcin = pyb.ADC(channel_to_read).read() | adcin = pyb.ADC(channel_to_read).read() | ||
ref_reading = pyb.ADC(0).read() | ref_reading = pyb.ADC(0).read() | ||
| − | supply_voltage = 4095/ref_reading*1.21 # or change 1.21 with the calibrated value - | + | supply_voltage = 4095/ref_reading*1.21 # or change 1.21 with the calibrated value - see below |
adc_voltage = adcin / 4095 * supply_voltage | adc_voltage = adcin / 4095 * supply_voltage | ||
</pre> | </pre> | ||
| Line 14: | Line 14: | ||
import stm | import stm | ||
factory_reading = stm.mem16[0x1FFF75AA] | factory_reading = stm.mem16[0x1FFF75AA] | ||
| − | reference_voltage = factory_reading/4095*3 | + | reference_voltage = factory_reading/4095*3 # will be approximately 1.21V |
| + | </pre> | ||
| + | |||
| + | For convenience, the library `onboard' provides the following functions for reading the battery voltage, unregulated voltage, or light level | ||
| + | <pre> | ||
| + | import onboard | ||
| + | onboard.get_battery_voltage() | ||
| + | onboard.get_unreg_voltage() | ||
| + | onboard.get_light() | ||
</pre> | </pre> | ||
Latest revision as of 00:50, 2 March 2017
See here [1] for the main micropython documentation.
All ADC readings are referenced to the supply rail, which is about 3.3V. To increase the ADC accuracy, the internal voltage reference can be read, and used to offset variations in the supply rail.
adcin = pyb.ADC(channel_to_read).read() ref_reading = pyb.ADC(0).read() supply_voltage = 4095/ref_reading*1.21 # or change 1.21 with the calibrated value - see below adc_voltage = adcin / 4095 * supply_voltage
Note, the factory reads the internal reference with a supply voltage of 3.0V, and stores this reading. This can then be used to get the actual voltage reference. For example
import stm factory_reading = stm.mem16[0x1FFF75AA] reference_voltage = factory_reading/4095*3 # will be approximately 1.21V
For convenience, the library `onboard' provides the following functions for reading the battery voltage, unregulated voltage, or light level
import onboard onboard.get_battery_voltage() onboard.get_unreg_voltage() onboard.get_light()