Recommendation for a solid yet cheap 3.3 Development Board?

Time comes to replace my old Arduino nano by a new type, on 3.3 V.

During forum conversations I got some useful hints about reliable 3.3. V boards. But I think is better to have a specific thread.

What I need the Board for:

  • sensors
  • small robots

mostly for educational purposes. So they have to be simple and cheap enough not to cry in clouds of smoke :-).

I do not need wi-fi.

What is your experience, please, with 3.3. boards? Thank you very much for sharing and for any hints!

What are your requirements? Why is a 3.3v pro mini or similar not appropriate?

No WiFi? Where's the fun in that?

@DrAzzy

Is education-centered. Kids.

Pro-mini 3.3.V is one alternative. I wonder if they are other options developed more recently.

To last longer. I spent half year with nano and now it looks like there are discussion about the genuine one will be kept alive.

In addition, I could not find the 3.3.V version of the mini in my area. Perhaps they plan to take it out as well?

There are some 3.3V "Adafruit Feathers" and "Sparkfun pro Micro" that are still Atmel-AVR based. The feather is part of a broad ecosystem - pin compatible boards with ARM, ESP, and 32u4 boards in addition to 328p boards.

Note that an AVR isn't spec'ed to run at 16MHz on 3.3V; you'll be getting an 8MHz board if you stick with AVR (and "staying within spec.")

Outside of AVRs, there are a lot of SAMD and ESP boards, (including the MKR series from Arduino) plus the PJRC Teensy 3.x boards.

Pro mini is good because of how dirt cheap they are, and how generally durable they are. You can supply a 25-person classroom with serial adapters and pro minis for like $100. They're generally tolerant of abuse, and they're all you need for "arduino as intro to programming concepts for kids" sort of application.

ESP8266 (or ESP32, for that matter) are great if you're doing a more advanced class, like highschool level, where you'll be having them connect stuff to the internet... And they're cheap, disposable, and fairly resistant to abuse.

Both of them also have an incredible amount of information on the internet about them because everyone, their mom, and their household pets is using them...

The "Blue pill" STM32F103C8 boards are also worth considering. You get 2 or 3 for the price of a beer and these have a well supported Arduino core. They are ARM Cortex-M3 MCU with 64 Kbytes Flash, 72 MHz CPU and 20Kbytes of RAM.
These boards outclass the Nano in all respects. However, a bit more effort to set up the first one.
The processor documentation is also excellent, which could be valuable if the main use educational.

The ESP series (previously mentioned) is also good but documentation and information there is often somewhat anecdotal and you will not be able to find processor documentation (Tensilica Xtensa) worth speaking of.

Hi
this so-called blue pill looks very interesting : is it compatible with the Arduino IDE or do we need any other software suit to program it?

It's compatible with the IDE using STM32duino, but my impression of that is that it's rather less mature than the AVR or SAMD board packages, and there's less material available online vs the ESP's (since it doesn't have the built-in wifi that so many people crave). I think it's going to be more difficult to get students up to speed with it, and harder to get the lab set up - I'm not sure the expanded capability of the board is worth it. It depends a lot IMO on what age group you're doing and how much time they're going to get to work with them.

True, setting up the first STM32F103C8T6 "blue pill" can mean a lot of fiddling around including registering with the chip manufacturers site to download 2 pieces of software, and some configuration in the IDE. There are also tales of dealing with boards which have a wrong resistor value which may affect USB ( I didn't suffer this). So there is a bit of a learning curve, even just trying to get the overview of the whole process. But that is a one-off effort.

It is well specified and if you don't need WiFi, it is well worth considering. However, you may have problems if you need libraries for some exotic devices.

I've just used one, incidentally, to make a GPS based clock for which used 3 of the 4 available hardware serial ports and the built in RTC (which I power with a Supercap) for a quick start following a power off.

STM32F103C8T6 in my area costs 10 USD/unit. The seller also posts an extended datasheet. The seller also specified that it is programmable via “JTAG or USART1”- which I do not know what means in practical terms.

For unknown reasons, the Arduino pro-mini sells here for 12 USD/piece in the 3.3 V version. The 5V version is 3 USD.

@6v6gt - what GPS module did you use?

JTAG is a standard interface/control protocol for accessing chips. It can be used for programming, debugging, testing etc. You buy an add-on device to use this interface Example: http://uk.farnell.com/stmicroelectronics/st-link-v2/icd-programmer-for-stm8-stm32/dp/1892523

USART1 is just Serial Port 1 (2 pins on the board). You can use an FTDI type programmer for this.

You can also use micro USB interface to program the chip. This is probably the most convenient, but you have to load an appropriate bootloader onto the chip.

For the GPS access, I used an AI Thinker A7 module. However, these come with an unusable GPS antenna. I made a small hack to the board so I could use an active GPS antenna.

These cost you $10 ? Is that the price you see in EBAY if you order direct from China or is that what a local retailer charges ?

Prices are from local sellers. The lower prices I can find.

For ordering abroad repeatedly adds up mailing costs very fast.

Many eBay and Ali Express vendors offer X5 or X10 quantities of the items which should reduce the postage costs considerably.

If you are considering 32-bit, 3.3V replacements for nano/Pro Mini etc., going for Arduino Zero/M0 compatible boards may be safer. AdaFruit offer two or three models based on the SAMD21 chip with different numbers of pins, and Sparkfun also have an offering. I am tempted to get an Itsy-Bitsy M0 from AdaFruit (despite the stupid name) to try out.

In this range (and on 3V) I can find here :

Adafruit Trinket Mini for some 11 USD

Adafruit pro Trinket for 12 USD

Also ATtiny85 Digispark for 4 USD (but this one looks a bit complicate)

WeMos D1 Mini ESP8266 is also available.

+++

I can find here Adafruit ItsyBitsy M0 Expres (in 3.3v), but is 20 USD. That looks fantastic in performance terms - I wonder if it can take abuse.

+++
ebay may be an option - thanks! but I would like to check first one unit. I am also reluctant to buy from ebay because of custom clearance.

+++

I’m all for supporting local vendors, but when they rip you off…

I can get Itsy Bitsy for £12 from a vendor <10 miles from here.

It sounds like amazing value until you remember you can get this for less money:

A-Star 328PB (Polulu)

I found references to this Board performances and practical use in the User's guide:

Frrom the User's manula, the Board has two I2C terminals. In my view (but is only a supposition) having two I2C terminals available could be useful for linking many sensors (grouping them in 2 groups, each group linked to one I2C terminal), so avoiding overcharge per terminal. But since the total load per Board is also limited and since the code shall be 2 branches rises some doubts to me in respect of practical use of 2 I2C terminals.

I am sill concerning about lack of direct info in the internet description about I2C capability. This lack of info may hide some problems in using the I2C (or maybe not).

The cost of this board is about 6 USD in local vendors (not sure is a genuine Polulu or a clone).