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→Improving the code
#
#
from machine import ADC, Pin
from machine import ADC, Pin
import time
adc = ADC(Pin(26))
adc = ADC(Pin(26))
temp = (mv-500)/10
temp = (mv-500)/10
print( 'Temp: %5.2f °C, Voltage: %4i mV' % (temp,mv) )
print( 'Temp: %5.2f °C, Voltage: %4i mV' % (temp,mv) )
time.sleep( 0.100 )
</syntaxhighlight>
</syntaxhighlight>
Which produce the following results
Which produce the following results into the MicroPython REPL/Shell
<nowiki>Temp: 15.19 °C, Voltage: 651 mV
<nowiki>Temp: 15.19 °C, Voltage: 651 mV
Temp: 14.71 °C, Voltage: 647 mV
Temp: 14.71 °C, Voltage: 647 mV
</nowiki>
</nowiki>
== Improving the circuit ==
You may notice some variation in the temperature reading. This is due to the DC/DC regulation using running at lower frequency (to spare power when really few current required by the project). At lower frequency, the voltage regulation is less efficient and 3V3 rail will be more noisy.
As the TMP36 only requires 50µA and RP2040 consume very few current, you may encounter this situation.
The following scope capture show the 3V3 rail at very low current. As shown, je 3V3 contains lot of noise (Saw Waveform).
[[Fichier:Pico-3V3-regulation-at-low-current.png|640px]]
As the analog sensors are very sensitive to unstable power voltage. Variation and noise on power rail may cause important variation on analog output of an analog sensor.
[[Fichier:Pico-TMP36-improved-wiring.png|480px]]
By adding the 2200µF capacitor, the noisy saw waveform will be changed and adding the 10nF will greatly reduce the noise opn the PowerRail.
[[Fichier:Pico-TMP36-improved-wiring-2.png|640px]]
== Improving the code ==
A good way to improve stability in the readings is to preform a means calculation over several reading.
<syntaxhighlight lang="python">
# Mean read the TMP36 analog temperature
# sensor wired to ADC0 (GP26)
#
from machine import ADC, Pin
import time
adc = ADC(Pin(26))
while True:
value = 0
for i in range(10):
value += adc.read_u16()
value /= 10
mv = 3300.0 * value / 65535
temp = (mv-500)/10
print( 'Temp: %5.2f °C, Voltage: %4i mV' % (temp,mv) )
time.sleep(0.100 )
</syntaxhighlight>
{{ENG-CANSAT-PICO-TRAILER}}
{{ENG-CANSAT-PICO-TRAILER}}