Hi,
We’ve all seen the Pico appear - as its got 4 analogue inputs would it be a suitable microcontroller
to monitor power? To be a cheaper emonTX?
Thoughts?
Are you sure? I can count 3, so the same as the emonPi in terms of power measurements, 1 voltage, 2 current - always assuming the ADC is up to the job (unlike ESP’s offerings), and it looks hopeful.
So it would be a very cut-down emonTx unless an external ADC was added.
page 6
• 30 multi-function General Purpose IO (4 can be used for ADC)
◦
1.8-3.3V IO Voltage (NOTE Pico IO voltage is fixed at 3.3V)
• 12-bit 500ksps Analogue to Digital Converter (ADC)
looking at the pinout theres
ADC_VREF
ADC0
ADC1
ADC2
I have no idea what the difference is between the VREF and C 0-> 3?
reading the manual:::
says “ADC_VREF is the ADC power supply (and reference) voltage, and is generated on Pico by filtering the 3.3V supply. This pin
can be used with an external reference if better ADC performance is required.”
thoughts?
The 4th analogue input (of the RP2040) is used internally (by the Pico) and isn’t brought out to be usable.
VREF is the ADC analogue reference voltage, like it says. An ADC doesn’t measure voltage, it compares its input voltage against a reference. Therefore if your 12-bit ADC gives a count of 1234, that means the input voltage is 1234 ÷ 4096 × VREF.
That’s annoying that they use an ADC internally - grrr!
so we have 3 ADC’s at 12 bits. Which isn’t bad for $4.
How many inputs does that mean we could monitor?
and if we had could stack the picos how many could the second get?
Might be easier using the i2c ports with an external ADC?
choices?
Whilst the Pico has just 3 ADC inputs accessible, there is actually something like 15 or 18 channels available on the Raspberry Pi manufactured chip that the Pico is based on (RP2040? IIRC) so other boards based on that chip could well have many more ADC’s made available. There were a couple of 3rd party boards mentioned in the RPF release article and one of those is very similar to the Pico but does have 4 available.