Raspberry Pi Pico use for PI detectors

[Olly]

I've been fiddling around with the Raspberry Pi Pico as it has some quite interesting features and is dirt cheap along with being very fast.
The programmable PIO's are particularly useful as all of the pulse generation can be offloaded to little state machines which run independently of the main code and timing is 100% repeatable.

It's also very easy to develop and debug with if you use Python along with the PIO assembler language.

I've included an example Python file which generates a main pulse along with sample and efe pulses if anyone is interested.

The built-in ADC's look like they are 12-bit and can sample at 500kHz but the reference may need tweaking to make it stable enough for real measurements.
pi.py.zip

[Qiaozhi]

Very good.
Apart from driving an OLED from the Raspberry Pi Pico I haven't done anything else with it, so this is interesting.
Since the Pico is quite new there's not a lot examples around.
You are currently the Geotech pioneer in this area.

[useus]

I am very interested in this project, I am of the idea that it can become a metal detector superior to 8-bit chips.

one would have to find someone who has expertise with python

[Olly]

I am very interested in this project, I am of the idea that it can become a metal detector superior to 8-bit chips.

one would have to find someone who has expertise with python

You can also use 'C' for programming but then you lose the convenience of the interactive Python REPL (console).
C will no doubt be faster, but the Python is actually pretty good and as long as all the timing critical paths are well defined in the PIO fsm's or other dedicated hardware then it's a great platform for experimenting with.

[MartinB]

Hi Olly
I would need some help on this one.
Never used Python or Raspberry Pi

[Olly]

Hi Olly
I would need some help on this one.
Never used Python or Raspberry Pi

Hi Martin
This is specifically the Raspberry Pi Pico, their new microcontroller board. Very similar in size and price to an Arduino, but very much more powerful. It is not the normal Raspberry Pi linux based computer board. If you take a look at the link below you should be able to get quite a bit of info. I bought mine from the PI Hut here in the UK.

https://www.raspberrypi.org/products/raspberry-pi-pico/

As I mentioned before, you don't have to use Python, I just find it very convenient as I've used it quite a bit before. There's quite a lot of online Python training and tutorials around, just a bit of searching needed .

The documentation link below also has a specific volume for getting going with Python on the Pico.

https://www.raspberrypi.org/document...tting-started/

Regards

[Olly]

I've found a really great article on generating waveforms with the Pico (see link below). It's a little bit complex but uses DMA and the programmable PIO along with an R2R DAC to generate waves in the background without intervention from the main code. Frequency changing on-the-fly should be relatively easy. I'm going to experiment with this and try to extract something useful in the way of audio tone generation to include in the Pi code. Watch this space!
https://www.instructables.com/Arbitr...pberry-Pi-Pic/

[MartinB]

Hi Martin
This is specifically the Raspberry Pi Pico, their new microcontroller board. Very similar in size and price to an Arduino, but very much more powerful. It is not the normal Raspberry Pi linux based computer board. If you take a look at the link below you should be able to get quite a bit of info. I bought mine from the PI Hut here in the UK.

https://www.raspberrypi.org/products/raspberry-pi-pico/

As I mentioned before, you don't have to use Python, I just find it very convenient as I've used it quite a bit before. There's quite a lot of online Python training and tutorials around, just a bit of searching needed .

The documentation link below also has a specific volume for getting going with Python on the Pico.

https://www.raspberrypi.org/document...tting-started/

Regards

Hi Olly
Thanks for the pointers - I will have a look over the weekend.
Something new to learn every day.

[Olly]

Hi Olly
Thanks for the pointers - I will have a look over the weekend.
Something new to learn every day.

Aint that the truth...
You know what they say about the half-life of an engineer

[useus]

I've found a really great article on generating waveforms with the Pico (see link below). It's a little bit complex but uses DMA and the programmable PIO along with an R2R DAC to generate waves in the background without intervention from the main code. Frequency changing on-the-fly should be relatively easy. I'm going to experiment with this and try to extract something useful in the way of audio tone generation to include in the Pi code. Watch this space!
https://www.instructables.com/Arbitr...pberry-Pi-Pic/

even this had already been discussed, in the comments of that article there are interesting features

[Olly]

Audio added

I've extracted the useful bits of the arb code for audio generation and added it to the example python program.
Also tested using a simple 8-bit R2R DAC as shown in the article and this actually works very well with audio frequencies from 20Hz to 20kHz without any intervention from the main program other than setting the frequency. (Actually the frequency upper range is around 1.25MHz but that's not much use for audio)
In a real design it would be a good idea to use the DAC output to drive a simple inexpensive headphone chip such as the LM4811 which also allows us digitally control the volume.
Next I'll look at fitting an external shunt reference to the ADC and see how useful it can be.
picopi.py.zip

[useus]

I've extracted the useful bits of the arb code for audio generation and added it to the example python program.
Also tested using a simple 8-bit R2R DAC as shown in the article and this actually works very well with audio frequencies from 20Hz to 20kHz without any intervention from the main program other than setting the frequency. (Actually the frequency upper range is around 1.25MHz but that's not much use for audio)
In a real design it would be a good idea to use the DAC output to drive a simple inexpensive headphone chip such as the LM4811 which also allows us digitally control the volume.
Next I'll look at fitting an external shunt reference to the ADC and see how useful it can be.
[ATTACH]55540[/ATTACH]

Maybe take pickini metal detector as an example and use lm318

[Vadim18]

Nice to see how RPI Pico metal detector keep growing, especially with python.
No doubt thanx to Oliver for great work
For audio id recomend to use pulse width modulation instead of analog output, one audio output transistor will save power (but i may think wrong).