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0 pointsdanhor2y ago0 comments

VQFN is quite possible using a soldering iron (the difficulty is the soldering pad underneath, but that isn't necessary and doable with suitable PCB design) . IMHO QFN is much easier to solder (and rework) than LQFN because bridges between two pads are easier to get away than bridges between the pins of QFP.

Pretty much no MCU in the same price range contains a DAC and most comparable MCUs don't have integrated OpAmps. The external flash has it's disadvantages, but it's also much cheaper to have huge amounts of flash. Typical 1$ MCUs can't include external flash in their address range, so it also can't be added in a similar way.

The RP2040 isn't suitable for a lot of floating point tasks, but floating point tasks on MCUs are not that common. FPGAs are often used as DSP-monsters and floating point isn't very nice on them.

If you need fast processing, with real multitasking, flexible (digital) pheriperals (PIOs can also simulate timers and up to ~22 total timers are nothing to scoff at), some nice fixed point DSP stuff (hardware divider, interpolators), gobs of (external) flash & RAM and great software support the rp2040 is pretty much the way to go as a default micro-controller.

For ~1$ it's a pretty compelling offer which is hard to beat with non-chinese chips.

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dragontamer2y ago

> Pretty much no MCU in the same price range contains a DAC

https://www.digikey.com/en/products/detail/microchip-technol...

10-bit DAC and Differential ADC at $1.00 right now at Digikey.

> most comparable MCUs don't have integrated OpAmps

STM32, AVR, and MSPM0 all have OpAmp chips in their family. No, not every chip. But this means that your assembly code / c-code and drivers just transfer over to the OpAmp family (Ex: AVR128DB48) when you need OpAmps.

So my code I wrote earlier on the AVR16DD14 $1 earlier just magically upgrades to the OpAmp version inside the family.

Bonus points to MSPM0 for having higher quality chopper/zero drift OpAmps even. (Though negative points for TI chips to be out of stock right now lol)

All of these are rail-to-rail in my experience as well. So.... Yeah... The competition is tough these days.

> If you need fast processing, with real multitasking, flexible (digital) pheriperals (PIOs can also simulate timers and up to ~22 total timers are nothing to scoff at)

Spend $5 more and get a real chip if you're actually processor limited. The Linux Capable SAM9X60 is sitting there at like $8. That's a full bore Linux 6.x kernel.

Anyone at the $1 to $3 market ain't doing this for cost/performance efficiency... but instead overall cost optimization. The 600MHz to Ghz class chips are all available at $10 and are a better choice for processor limitations.

If you're scared of BGA, then I'm still willing to bet that STM32F7 or STM32F4 are better choices with hardware Floats and like 200MHz to 800MHz.

But yeah, 8-bitters and Cortex-M0+ chips aren't here to win performance or compute benchmarks. They're here because a potato-chip is all you need to run an ADC + send data over SPI or I2C and/or react to a UART. For all deeper needs, please for good gracious... please buy a $3 or $5 or $8 chip instead.

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I do think the $1 to $3 market is mostly about "Making sure you don't have to buy something else". Like having on-board flash (cutting off another $1 from the BOM / assembly), or whatever.

RP2040 goes a different approach, $1 is very cheap and 264kB is a very large amount of SRAM, but it really doesn't contain anything else worth noting (I guess a single-ended ADC and the PIOs like you mentioned). But all the SRAM/PIO in the world isn't enough to get you to output a 10-bit analog signal through a DAC.

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