Author Topic: Raspberry Pi Pico  (Read 36831 times)

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Offline tszaboo

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Raspberry Pi Pico
« on: January 21, 2021, 10:32:51 am »
The new flexible $4 microcontroller board from Raspberry Pi
https://www.raspberrypi.org/products/raspberry-pi-pico/
Quote
Designed by Raspberry Pi, RP2040 features a dual-core Arm Cortex-M0+ processor with 264KB internal RAM and support for up to 16MB of off-chip Flash. A wide range of flexible I/O options includes I2C, SPI, and — uniquely — Programmable I/O (PIO). These support endless possible applications for this small and affordable package.

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Offline tszaboo

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Re: Raspberry Pi Pico
« Reply #1 on: January 21, 2021, 10:51:11 am »
What I like:
- Castellations for SMD mounting
- Micropython
- price, if it is not waporware like the zero
- Doesn't use that terrible Italian IDE
- Not just an LDO, but an SMPS
- Based on the model number, other types/memories are coming
- Remap of the communication ports
- Recovery mode with USB, no matter what you do

What I dont like:
- Microusb instead of USB C
- Sleep current is more than 1 mA for the board, and 180uA for the micro alone <- This should be 10 uA max for the micro, and 100 for the board.
- No wireless
- No RTC
- Only 4 ADC pins, only 3 on the board

Probably it will be insanely popular.
« Last Edit: January 21, 2021, 11:06:17 am by NANDBlog »
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Offline kjw

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Re: Raspberry Pi Pico
« Reply #2 on: January 21, 2021, 11:04:46 am »
There's a lot on this new board in HackSpace Issue 39.

I'm still reading about it but so far I observe:

  • Amazing price which makes it very accessible.
  • Likely to have a huge amount of supporting material, there's already a MicroPython book for it.
  • Not much on the Pico board so needs extras unlike say the BBC micro:bit.
  • Pimoroni already have a huge range of interesting looking products to work with it.
  • Two M0 cores - curious decision as that means no hardware floating point, limited language support, hard to use both of them especially for beginners.
  • PIO look very useful.
  • ADC is limited to three pins on Pico (four on the RP2040) - that's a bit of a shame if it's used on existing boards.
  • No DACs (an incaccessible one tucked away inside the SAR ADC)
  • Interesting concept of using one board to debug another using SWD known as "the Picoprobe".
  • Unintentionally fragments the microcontroller-for-beginners world.
  • Thankfully does not maintain the Raspberry Pi tradtion of unlabelled pins, the underside of the Pico board has the pin names on!
  • May not be available with headers pre-soldered onto the board.

We could all add the usual I'd like it to have A, B, C features but most of those are expensive and they've clearly tried to keep this around 4 USD.
« Last Edit: January 21, 2021, 11:55:20 am by kjw »
 
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Offline gmb42

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Re: Raspberry Pi Pico
« Reply #3 on: January 21, 2021, 11:05:35 am »
And other vendors doing their own boards\systems with the RP2040:

Arduino:

AdaFruit Feather: https://www.adafruit.com/feather2040
AdaFruit ItsyBitsy: https://www.adafruit.com/itsybitsy2040

SparkFun Micromod:
SparkFun Thing Plus: https://www.sparkfun.com/products/17745
SparkFun Pro Micro: https://www.sparkfun.com/products/17717

Pimoroni PicoSystem: https://shop.pimoroni.com/products/picosystem
Pimoroni other pico products: https://shop.pimoroni.com/?q=pico

Cytron Maker Pi Pico: https://www.cytron.io/p-maker-pi-pico

h/t to CNX Software
 
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Offline aheid

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Re: Raspberry Pi Pico
« Reply #4 on: January 21, 2021, 12:35:40 pm »
FFS an 133MHz CM0+, with off chip flash.
The specifications[1] says it has 2MB on-board QSPI Flash.

[1]: https://www.raspberrypi.org/products/raspberry-pi-pico/specifications/
« Last Edit: January 21, 2021, 12:38:00 pm by aheid »
 

Offline aheid

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Re: Raspberry Pi Pico
« Reply #5 on: January 21, 2021, 12:37:29 pm »
 

Offline up8051

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Re: Raspberry Pi Pico
« Reply #6 on: January 21, 2021, 12:38:39 pm »
Also the price :palm:. $4 in China gets you an FPGA board or a Linux-capable MPU board.

If I buy from China, I have to wait 3-4 weeks or longer, or the package does not arrive at all
I never know what I will really get (counterfeit BluePill, Atmega328PB ...), often lack of description and documentation.
I can buy Rasspebry Pi Pico locally with good support.
Price is not always the most important thing.
 
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Offline aheid

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Re: Raspberry Pi Pico
« Reply #7 on: January 21, 2021, 12:51:13 pm »
Hence the "off chip" part.

:palm: clearly I need more sleep!
 

Offline aheid

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Re: Raspberry Pi Pico
« Reply #8 on: January 21, 2021, 12:56:45 pm »
in order not to choke the cache-less CPU
Reading the datasheet it says
Quote
2.6.3.1. XIP Cache
The cache is 16 kB, two way set-associative, 1 cycle hit. It is internal to the XIP subsystem, and only affects accesses to
XIP flash, so software does not have to consider cache coherence, unless performing flash programming operations

So it's not entirely cache-less, though I have no idea how far it'll get ya.
 
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Offline aheid

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Re: Raspberry Pi Pico
« Reply #9 on: January 21, 2021, 01:28:20 pm »
- Sleep current is more than 1 mA for the board, and 180uA for the micro alone
The chip datasheet says
Quote
Note also that DORMANT does not halt PLLs. To avoid unnecessary power dissipation, software should power down PLLs before entering the DORMANT state, and power up and reconfigure the PLLs again after exiting.
However from what I can see the "hello_dormant" example used for the 180uA number in the power consumption table does not power down the PLLs?

So maybe potential for a bit better deep sleep performance.
 

Offline Berni

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Re: Raspberry Pi Pico
« Reply #10 on: January 21, 2021, 01:32:38 pm »
It is internal to the XIP subsystem, and only affects accesses to
XIP flash, so software does not have to consider cache coherence, unless performing flash programming operations
Um, there goes your timing determinism.

The timing determinism is already out the window in the "main thread" as soon as you use interrupts anyway, just stick the interrupt service routines into RAM and its sorted. Those typically have a minimum of code in it, so they tend to also result in not that much machine code to store.

This sort of execution directly from external flash has gotten popular with other vendors too, for example NXP has whole lines of micro-controllers with no internal flash. They claim they are doing this because doing large amounts of flash on a fab process optimized for making CPUs is not very efficient and ends up taking up a lot of die area.

 

Offline Ice-Tea

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Re: Raspberry Pi Pico
« Reply #11 on: January 21, 2021, 02:15:51 pm »
Would have been 100% more awesome if it had even the poorest possible WiFi capability...

Offline JPortici

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Re: Raspberry Pi Pico
« Reply #12 on: January 21, 2021, 02:17:47 pm »
"daul core cortex M0+"
why?
why?
WHY?

also HOW?
 
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Offline Cliff Matthews

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Re: Raspberry Pi Pico
« Reply #13 on: January 21, 2021, 03:42:01 pm »
Cheap! Just ordered one  :popcorn:  Perhaps I'll try running the built-in MCU's as a dual channel ARB..
 

Offline CJay

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Re: Raspberry Pi Pico
« Reply #14 on: January 21, 2021, 03:42:59 pm »
Would have been 100% more awesome if it had even the poorest possible WiFi capability...

Given the Pi foundation's history I'd suspect there's a WiFi version in the works.

Have ordered two to play with but not exactly enamoured of the idea of a Pi dev environment and I'm hopeful there'll be a version that works on a 'larger' machine
 

Offline Monkeh

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Re: Raspberry Pi Pico
« Reply #15 on: January 21, 2021, 03:46:02 pm »
Would have been 100% more awesome if it had even the poorest possible WiFi capability...

Given the Pi foundation's history I'd suspect there's a WiFi version in the works.

Complete with awkward, half-documented, likely full of security holes Broadcom firmware.
 
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Offline SiliconWizard

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Re: Raspberry Pi Pico
« Reply #16 on: January 21, 2021, 04:29:05 pm »
The new flexible $4 microcontroller board from Raspberry Pi
https://www.raspberrypi.org/products/raspberry-pi-pico/
Quote
Designed by Raspberry Pi, RP2040 features a dual-core Arm Cortex-M0+ processor with 264KB internal RAM and support for up to 16MB of off-chip Flash. A wide range of flexible I/O options includes I2C, SPI, and — uniquely — Programmable I/O (PIO). These support endless possible applications for this small and affordable package.

Yeah, saw that as well.

I'm not sure this product really makes sense.
Looks like the Raspberry foundation wants to get into the microcontroller territory... but given the absolutely HUGE offering in that market, I don't see the point. Really. It has nothing to offer compared to what already exists, not even the price.

IMO, the RPis are powerful but are not adapted for the kind of low-level tasks a MCU allows, so a smarter product IMHO would have been a new RPi with an associated MCU, a decent SDK and good linux drivers to communicate between the main SOC and the additional MCU. Alternatively, it could be a new RPi with an associated FPGA on board.

Another smart move would be to finally design a product that is fully open, with either an open-source (we can dream) SOC, or at least a SOC that is fully documented and doesn't require to sign with your blood to get access to the docs.

Just my 2 cents.
 

Online ralphrmartin

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Re: Raspberry Pi Pico
« Reply #17 on: January 21, 2021, 04:54:50 pm »
I don't get the point of this (unless its to make money off the RPi name, and I doubt that given their charitable aims).
There are any number of small boards similar to this, of one kind and another, that already run micropython, or beat this price, or have better peripherals, or better processors, or are better in some other way. There are boards from manufacturers or Ardiuno if you want brand names, or anonymous ones if you want a very low price. In short, I dont see what perceived gap in the market (or educational space, if you are coming from a charitable rather than commercial angle) this is trying to fill.
 

Offline ataradov

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Re: Raspberry Pi Pico
« Reply #18 on: January 21, 2021, 05:25:04 pm »
Guys, calm down. This is the same things as SiFive FE310. They did a test chip and decided to release it to public to make some R&D money back. Normal vendors do this all the time, but don't release half baked stuff.

It is a cool toy, nobody expects anyone to use it in real projects. But hobbyists, as usual, will find a way to use the device to its fullest performance level. And those projects will show the bottlenecks that could be improved in the next design.

The next iterations would improve on the design, not everything at once.

And for the first product, they are doing everything right. Out of the gate, they have great documentation. I really wish "real" part datasheets looked like this.
« Last Edit: January 21, 2021, 05:26:56 pm by ataradov »
Alex
 
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Offline dcarr

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Re: Raspberry Pi Pico
« Reply #19 on: January 21, 2021, 05:31:50 pm »
Speculation on the dual cores:

Many wireless ICs have dual cores---one for application code and the other for the wireless side of the house.

Seems to fit in nicely with the theory that this is/was a test chip on the road to a wireless MCU product.
 

Offline Syntax Error

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Re: Raspberry Pi Pico
« Reply #20 on: January 21, 2021, 05:49:26 pm »
My jury is out on this... Maybe they slashed costs so far, all they built was a Microbit with one LED? Harsh? This segment of the microcontroller maker market is so over saturated right now. Not one brand is able to deliver a knock out product. Instead, the market is a PacMan like maze of look-alikes and their clones. (zigbees are the ghosts btw)

So how are we meant to mount this; on a breadboard, on a veroboard, on a custom breakout motherboard? Nice they put the GPIO silks on the under-side then. So which way is up? And 2MB of flash not 4? That would double the price.

However, being able to use as a USB host might just edge this into my shopping basket. WTF it's cheaper than a decent quality USB lead. Sold.

In future, pehaps sacrifice one spi channel for use with an ESPxxxx. There is certainly space where that big Pi logo is for a Wifi or BLE subsystem, plus aerial. But then it might start to look like a NodeMCU. Or a Yun. Or a Zigbee.
 

Online rstofer

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Re: Raspberry Pi Pico
« Reply #21 on: January 21, 2021, 06:05:58 pm »
I have no idea why I ordered 4 Pico's and the book but it should be entertaining.

I don't know if the board/chip has a future but look at the ATmega328P.  Who would have thought that chip would become as popular as it has.  It really has nothing special to recommend it.
 
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Offline ataradov

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Re: Raspberry Pi Pico
« Reply #22 on: January 21, 2021, 06:08:59 pm »
I have no idea why I ordered 4 Pico's and the book but it should be entertaining.
I ordered a few before they run out, as typical for RPi. I have no real use for them, but hey, it is a new part from a new vendor, let's check it out.

I also  expect that programmable I/O controller may be used in some creative ways.

And unlike new cool parts I want to try from Chinese vendors, this one has a real datasheet that is already better than anything else in the industry.
« Last Edit: January 21, 2021, 06:10:59 pm by ataradov »
Alex
 

Online ralphrmartin

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Re: Raspberry Pi Pico
« Reply #23 on: January 21, 2021, 06:18:06 pm »
The next iterations would improve on the design, not everything at once.

As they say, you don't get a second chance to make a first impression.
 

Offline ataradov

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Re: Raspberry Pi Pico
« Reply #24 on: January 21, 2021, 06:22:55 pm »
As they say, you don't get a second chance to make a first impression.
Yes, but I personally am very impressed by this thing. It is a functional MCU (apparently, we'll have to see, of course) with excellent documentation. Sure, it lacks some peripherals, but so are many other MCUs on the market. There is nothing exceptional about it, but it is not bad, which is something you can only hope for for your first part.

Off-chip flash will be a more common approach in the future. It may be stacked dies without an external flash IC, of course. Flash is a pain to manufacture on the same die as the logic. And QSPI/Octal flash can be as fast as internal one, given wait states.
Alex
 
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