Microcontroller Dev Boards: What features do you like to have (or to add?)

I disntiguish three types of board usualy refered as:

• Breakout/prototyping boards. Examples: Raspberry Pi Pico, STM32 Blue Pill
• Development Kit. Examples: STM32 Nucleo, STM32 Discovery, Renesas EK-RA, Cypress PSoC Pioneer boards, SIlicon Labs Explorer Kits, Microchip Curiosity Nano, Maxim FTHR boards, Nordic nRF52, nRF53 and nRF91 devkits
• Evaluation Kit: STM32 Evaluation Kits

The first is simple. No necessary connectors, components and so on. Usualy they have exposed all or almost all pins. They are good for low-power applications because except MCU there is nothing else consuming energy.

Difference between second and thinrd is in the scope of offered feature. The last should allow user to evaluate ALL features of the MCU while the middle option allows using (smartly selected) subset of the feature. Most devkits are in second group. I guess it is because second group offer best price/performance ratio. First category is good for low-pin MCUs but for higher count MCU it became annoying. Second category offsers good onboard peripherals and allows use most of features without heavy external circuits. Third option is used for users who have needs for heavily using the MCU and need to develop firmware before make prototypes of their own huge boards. Third category is the most expensive, but this boards often contains tons of connectors, sensors, large displays, several connectivity options,... In other words evaluation board (like this one) contains everything but are expensive.

Nowadays almost every board (currently also including many board classified to first category) has onboard JTAG/SWD debugger and we do not need buying expensive external debugger anymore. It is extremely usefull benefit in comparison with boards avalaible 15 years ago.

My most favourite development kit design is Renesas EK-RA like EK-RA2L1 which I reviewed as part of roadtest: Review of Renesas EK-RA2L1 Development Board

It has very few onboard peripherals, but has lot of connectors for most commonly used interfaces: Arduino Uno compatible connector, MIkroE socket, Qwiic, Grove, PMOD. Except these connectors all pins are accessible on dedicated connectors. It is very usefull for connecting logic analyzer. I like this design very much. Other very good options is that all devekits in this serie share the same design, so if you ware familiar wiht one kit, you can freelky move to the other one. They are expensive, but Renesas offers free samples

Second boards which I frequently use are STM Discovery and Nucleo boards. Nucleo shares the samilar design pattern as Renesas EK-RA. In case of STM I like discovery boards over Nucleos because disco boards add some interesting peripherals.

Nowadays many vendors try to standardize even their breakoutable/prototyping boards. For example recently I played with Silicon Labs EFR32BG22. Silicon labs makes their explorer kits which all have the same (small) form factor, onboard debugger, MikroE socket and exposes all other pins. They use this form factor for all their MCUs no matter if they support BLE or not, are 8-bit or 32-bit and so on.

At last I like boards which has something very unique and advanced but vendor designed to offer them at very competitive price for promoting their products. For example MAX78000FTHR. I basicaly described it in my blog  Received Project14 7-segment Display Competition Reward . It is 30 USD board with advanced dual core MCU with AI accelerator, on-board debugger, camera, audio codec (+ jacks), other MEMS microphone and allows running from battery (has on-board li-pol/li-ion charger). Very few boards are so tiny, so performant, so cheap and allows so much interesting use cases. But it has other disadvantage like hard firmware development.

Another benefit of large boards is that they can house a lot of project : ) That trainer board's breadboard area could be used to carry a PCB or stripboard or perfboard etc, just placed or pushed on top. I do the same thing on the Pico board.

I was experimenting with audio in the photo here. Since this amplifier board needed 12V, I could take that power from the screw terminals visible at the right side of the photo, powering everything from the single barrel connector.

I don't use many MikroE Click boards, but I needed one here, so I prototyped a Click adapter to plug on top. Actually normal stripboard/perfboard can be plugged on, but I had a few older revision Pico Eurocard boards so I cut one in half to plug on top here. Might as well reuse scrap boards if possible:

GPIO pins in order can help sometimes; the connector on the right side is organized in that order, so the LED 7-segments could be nicely in A-G segment sequence on the header:

Soldered parts on the main area:

The parts are really easy to desolder (so that the board can be reused many times)  because of this; there's a gap between the holes and the pads:

Incidentally, 30 AWG wire is always handy to have on hand for creating projects/fixing circuit board problems etc.

It had really nice machine code (very good for the C compiler!) and had UART bootloader. Meanwhile, even the much later (by a decade or more) PIC microcontrollers were completely missing that, requiring a relatively expensive programmer (about $150-$200 from memory).

I couldn't afford expensive programmers, so tended to use nice chips like the 68HC11 series, and also the Hitachi H8 series (they had UART bootloader too, and rich instruction set). 

beacon_dave said:

Shabaz' board looks more like a dev board that might be used primarily for developing a single project prior to a first PCB design

I agree the definitions are vague. (Admittedly, I did not define "development board" on purpose.)

That said, the two boards, in my opinion, are extremely similar. The biggest difference is that the top board supports multiple microcontrollers, while Shabaz's only supports the Pi Pico. Both accept microcontrollers, support flexible power supplies, and have a handful of useful peripherals across multiple projects.

Stacking connectors are also very useful on some dev cards.

I felt the same : ) On the revision 2 board that is in the photo above, the text still feels small, so on the more recent rev 2.2 board the text labels for each pin are bigger where possible. 

Actually, that's another desirable requirement for dev-boards, to have the text all oriented one direction (i.e. not having to read text sideways). This is not always practical though.

The rev 2.2 also has a few minor changes, such as locating all the surface-mount parts, including the micro SD connector, on the underside, to be easier to assemble):

Wish there was an option for glow-in-the-dark silkscreen : ) Or there could be lit dev-boards with small LEDs illuminating it to be able to always read the text clearly. One simple way to do that : ) could be a wood box/tray around dev-boards, with LED strips pointing inward : ) I'm surprised Arduino etc do not offer that! : ) 

It's great to see how the community comes together to create and share different microcontroller development boards! Here are some features that I think many users would like to see in a microcontroller development board:

• Breadboard compatibility: A development board that is breadboard-friendly makes it easier for users to prototype and test their circuits quickly.

• Multiple power options: Having the flexibility to power the board through USB, an external power supply, or a battery can be beneficial for various projects.

• Built-in debugger/programmer: A built-in debugger/programmer can simplify the development process and eliminate the need for external tools.

• Comprehensive documentation and support: Detailed documentation, examples, and tutorials can help users get started and make the most of the development board's features.

• Wide range of GPIO pins: A development board with a sufficient number of GPIO pins, including digital, analog, and PWM pins, provides flexibility for different project requirements.

• Connectivity options: Built-in support for communication protocols such as I2C, SPI, UART, and USB, along with wireless options like Wi-Fi, Bluetooth, and LoRa, can enhance the versatility of the development board.

• Expandability: A development board with expansion headers or slots for additional modules, shields, or HATs allows users to add more functionalities to their projects as needed.

• Onboard sensors and peripherals: Including basic sensors (temperature, humidity, accelerometer) and peripherals (LEDs, buttons, displays) on the development board can enable users to experiment with various components without the need for external modules.

• Robust voltage regulation and protection: A development board with efficient voltage regulation and protection circuits ensures stable operation and safeguards the board from potential damage.

For me the biggest issue with some of the dev boards I've played with are the "gotchas".

Such as pins labelled as TX and RX but then are not actually usable as serial as they are wired to something else such as a WiFi module. Or something as simple as a pull-up or LED meaning you can't use a particular pin in the way you intend. 

Or where the underlying processor supports multiple PWM but the board can't because of the eco system not supporting it.

BE, the Practical IOT Microcontroller Trainer Rev 2.0 has been retired (https://www.tindie.com/products/bluesmokemonster/practical-iot-microcontroller-trainer-rev-20/ ). Do you have any updates on the product?

The creator is a friend of mine. He started working on a Rev 3 a while back. During the parts shortage, he could not get parts for the redesigned power supply. So it went on the back burner.

To be upfront, I used the image here to poke him about the project. But it seems unlikely he'll come back to it any time soon.

So, no updates, sadly.