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I think he's doing an important analysis, but not for DIY hobbyists: knowing how cheap your SoC is only makes sense when you're finalizing a BOM for mass produc
by DiabloD3 4y ago
I think he's doing an important analysis, but not for DIY hobbyists: knowing how cheap your SoC is only makes sense when you're finalizing a BOM for mass production, even if they're small runs. The SoC is only one component of at least a dozen required to make a working microcontroller board.
If you're doing DIY hobbyist yourself, you'll want to buy pre-mounted SoCs in a known form factor (as in, it is on a tiny daughter board, and that board has a known pin-out that remains consistent across clones). Example: the Pro Micro.
A Raspberry Pi branded Cortex-M0+ on a Pro Micro clone board sold under the Sparkfun brand is $11: https://www.sparkfun.com/products/18288 https://www.sparkfun.com/products/18288 All the components to have a fully working microcontroller out of the box is included; the SoC, RAM, flash, USB connector, the rest, and it's all machine placed and soldered, and individually tested.
The dev board of the SoC he selected is $5, but get shipped from China and seem to be incomplete dev kits (no USB, no flash reprogramming pins, and the docs aren't great); it also doesn't seem to be a standard/popular form factor.
The analysis in the article is only the part that would lead you to "if I wanted to make my own Pro Micro-sized microcontroller, which SoC is cheap but good"; you still need the cheap but good equivalents for the rest of the components and then actually be able to solder it (SMD components suck for humans to hand place).
- technothrasher 4y agoIt was an interesting read for me, as I build professional boards from scratch using LPC and STM series chips at work, and so have the tooling to play around with cheapy things like this on a DIY hobby basis. I usually don't like to go with the pre-built SoC boards because they do it differently than I like, and since I have the resources to do it my way, I can.
- dragontamer 4y agoRP2040 has zero flash on board and is a terrible chip to use as an example. Its actually a lot more complex to boot up than other chips, and I personally consider it closer to a microprocessor than a microcontroller (its somewhere in between). STM32F0 is a cheap Cortex M0+ that has on-board flash and on-board oscillator. Other Cortex M0+ parts are similar (with the RP2040 as a massive exception). This means that the board design is extremely simple. --------- > the SoC, RAM, flash, USB connector, the rest, and it's all machine placed and soldered, and individually tested. Case in point: STM32F0 has RAM, Flash, Oscillator all on the SoC. Just apply Vcc + Ground and your code is running. I guess programming is somewhat difficult, but sockets do exist for a variety of form factors. ZIF sockets for DIP are cheap, looks like the sockets for STM32F0 (64 quad flat package) are a bit pricy though. But an "on board" chip programmer is simple in my experience. STM32 / Microchip SAM Cortex chips are designed to be easily programmed and prototyped. -------- I think you're right in that hobbyists ought to start with developer boards. USB "makes sense" to a lot of people. But I also want to encourage hobbyists, even advanced beginners, to mess with chips directly. Some chips are much easier to bootstrap than others. Yes, even on a breadboard. https://www.brennantymrak.com/articles/programming-avr-with-arduino https://www.brennantymrak.com/articles/programming-avr-with-...
- benj111 4y agoThe linked board includes flash. If you're going down the route of buying a board why should you worry about the complexity of putting it all together?
- dragontamer 4y agoA lot of uCs have flash on chip, that makes integration easier. RP2040 is harder because it won't even boot until you add flash. Other chips however will boot with just Vcc and Gnd (aka + and - power applied). That's my point. Many many chips are actually really easy to build a board around. But not RP2040.
- DiabloD3 4y agoUpdate: Adafruit sells a RP2040 in a Pro Micro clone for $9: https://www.adafruit.com/product/5302 https://www.adafruit.com/product/5302, otherwise seemingly identical as the Sparkfun RP2040 Pro Micro clone. That makes it about as cheap as real ATmega32u4-based Pro Micros, which are still hard to find due to the chip crunch.