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Update read for continuous #57

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Merged
merged 1 commit into from
Jun 28, 2020
Merged

Update read for continuous #57

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10 changes: 9 additions & 1 deletion adafruit_ads1x15/ads1x15.py
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@
__version__ = "0.0.0-auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_ADS1x15.git"

import time
from micropython import const
from adafruit_bus_device.i2c_device import I2CDevice

Expand Down Expand Up @@ -161,7 +162,10 @@ def _read(self, pin):
if self.mode == Mode.CONTINUOUS and self._last_pin_read == pin:
return self._conversion_value(self.get_last_result(True))
self._last_pin_read = pin
config = _ADS1X15_CONFIG_OS_SINGLE
if self.mode == Mode.SINGLE:
config = _ADS1X15_CONFIG_OS_SINGLE
else:
config = 0
config |= (pin & 0x07) << _ADS1X15_CONFIG_MUX_OFFSET
config |= _ADS1X15_CONFIG_GAIN[self.gain]
config |= self.mode
Expand All @@ -170,8 +174,12 @@ def _read(self, pin):
self._write_register(_ADS1X15_POINTER_CONFIG, config)

if self.mode == Mode.SINGLE:
# poll conversion complete status bit
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I would throw these comments up in the function definition comments to describe how this works in the context of the whole function.

while not self._conversion_complete():
pass
else:
# just sleep (can't poll in continuous)
time.sleep(2 / self.data_rate)
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@zacnelson zacnelson Jun 26, 2020 •
edited
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According to the ADS1115 data sheet (and also the ADS1015) the conversion time is 1 / DR:

9.3.6 Output Data Rate and Conversion Time
The ADS111x offer programmable output data rates. Use the DR[2:0] bits in the Config register to select output
data rates of 8 SPS, 16 SPS, 32 SPS, 64 SPS, 128 SPS, 250 SPS, 475 SPS, or 860 SPS.
Conversions in the ADS111x settle within a single cycle; thus, the conversion time is equal to 1 / DR.

@caternuson Any particular reason you chose 2 / DR?

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I tried 1 / DR first and it didn't seem to work. Might have something to do with extra settling time needed due to the mux being changed? Not sure.


return self._conversion_value(self.get_last_result(False))

Expand Down