3 ms·

I have mixed feelings about the RP2040. On the one hand, it's a great chip for hobbyists. It's cheap, it's easily available, it's easy to build a board around,

by crote 2y ago

I have mixed feelings about the RP2040. On the one hand, it's a great chip for hobbyists. It's cheap, it's easily available, it's easy to build a board around, and it offers plenty of stuff for your average application. On the other hand, it's definitely a bit lacking from a professional perspective. The peripherals are fine, but once you start looking into the details it's easy to run into limitations. That XIP interface is great - but it doesn't support writing so you can't hook up an FRAM chip and expand your memory. That PIO interface is amazing - but having only 2x32 instructions is quite limiting once you try to implement more complex interfaces. And where are my Timer/Counters? No capacitive touch? Analog on only four pins? No 5V tolerance? No high-speed clock input for the PIO modules? Why can't I run the bootloader off the internal ring oscillator? Hmm, a USB-C PHY sure would've been helpful... I was also surprised about its poor ESD performance. An Atmega or STM32 can handle the occasional zap just fine - ESD protection is more of a nice-to-have on external-facing ports. The RP2040? If you don't add external protection to every single pin you are basically guaranteed to see a few of them die due to day-to-day use. To summarize: neat chip, great for hobbyists, wouldn't be my first choice in professional environments.

doubloon 2y ago
Raspberry pi was originally an educational non profit
dfox 2y ago
I suspect that the Synopsys DesignWare SSI macro in RP2040 can in fact be used for R/W PSRAM or FRAM, but the abridged documentation of it in RP2040 datasheet is not sufficient for one to configure it that way.
- crote 2y ago
  Ooh, good point! I should definitely look into that.
stefan_ 2y ago
What do you mean by USB-C PHY? USB-C is the connector, and you can run USB 1.1/2.0/3.0/3.1 through it, but realistically a RP2040 can not feed even a USB 2.0 PHY.
- 15155 2y ago
  The USB version doesn't directly imply link speed - USB 2.0 devices can be LS, FS, HS. The RP2040 can handily saturate LS/FS links. With PIO or the SPI master and DMA you could absolutely make use of a USB HS PHY.
- crote 2y ago
  A PHY for the USB PD communication over the CC wires. That makes it possible to negotiate things like Alt Modes for a USB-C connector. DIYing one is surprisingly hard due to the voltages and timing involved.
ChiefNotAClue 2y ago
Well said. I'll add that, as a hobbyist, you'll eventually work on more involved projects and run into those exact limitations.
kragen 2y ago
i'm curious what kinds of applications you've found fram most useful for. it seems like a really cool technology, but the price point is so high that i struggle to understand when you'd use it rather than a combination of sram (or psram) and nand
- dragontamer 2y ago
  I assume that most people's use of FRAM is when its integrated into TI's MSP430 microcontrollers IE: if FRAM comes free with your MCU, might as well use it and take advantage of its benefits. For example: MSP430FR4132, just picking one such MCU off of Digikey (https://www.digikey.com/en/products/detail/texas-instruments/MSP430FR4132IG56/5067015 https://www.digikey.com/en/products/detail/texas-instruments...) ------ Most of what I know of FRAM comes from TI's marketing pages. https://www.ti.com/document-viewer/lit/html/SSZTA32 https://www.ti.com/document-viewer/lit/html/SSZTA32
  - kragen 2y ago
    probably so, but crote was talking about external fram chips the msp430fr4132 you linked costs 160¢ in quantity 35, which is actually considerably cheaper than comparable flash-based chips like the msp430f233 https://www.digikey.com/en/products/detail/texas-instruments/MSP430F233TPMR/1784864 https://www.digikey.com/en/products/detail/texas-instruments... which is 500¢ in quantity 25. so that's maybe one reason people would use fram: evidently it's cheaper than nor? but i'm pretty sure there are μcs with 8k of nor flash that are cheaper than that and in fact cheaper than the price difference. is this pricing policy some sort of loss leader by ti to drive fram adoption? it seems unlikely. does using fram instead of nor make it cheaper for ti to make the chip? surely 8k of nor couldn't account for such a large cost on further investigation, i don't find μcs with 8k of nor flash that are cheaper than that, at least in stock at digi-key and still in production. https://www.digikey.com/en/products/filter/embedded/microcontrollers/685?s=N4IgjCBcpgrLVQGMoDMCGAbAzgUwDQgD2UA2iAEwUDs1ALNSIVbXQBxOUAMbAzLxGbtYvCpwoA2CdQpdxUmYMoKKvcWy4BOLnU51NvOl0bNqXWNvGa6quc2uqx9m7wTPVE9UYpLe5rSYg1IawgWzUYIac4ZFuIDG8noQJgfqG5pyaEgZqhGBcflKZbBIUcfkaYJqcFVyyNTx15Y00DRoUHIR0%2BmCteWASvYFgNll24KODNbB00sMz0p3gC9TVeQsaNRIzm10GRkngUn654GxsRuNg50ZK1xd1NTcZec%2BH1xIX5Zpmmk6UIxkgR8DA64jK4X%2BVFg4VO0PCumYEOocW2BnO4gO4UxvBRcQo3WswMJ7Ex%2Bn0nBkGk0SzKVKUdI6-0UbE0%2BIsIkOZTZuPEHN4tMGIjWyjgRnkYsRop28h49HkAoECr4UO2onGHRk8HUWq5BjgcT8AUNXAChxOqiWFt4Iot4sIfjorhFtDZgVW12Zmmupwe12itxFD3qyVgBMOJTqUpKsFN0W2j2SCd9CcO2m2hyd7B0mXg3oa%2BS4d3MbAGNWusfeFeM5bYsaWIwKNum1GyUrgqx%2BLc0NOmGkTy378w0s040lCMK2sA%2BT2C3SepciY7rNpFVR%2B%2BXEAw6Gpt-Che-44kP%2BL3EilqgMRUI2VoEUxVCmQgs9sosykXMGBWB1Bid1k07lABIbgMBSh0AM2x6AStB6MEuzxAUkT-PAoinDMNpXJ8mo1KoeY1AIqwanUAynJMvJIr%2BdbiDopRKBEZhQYQDFcNeIDZNo%2BbMFIpZLCx0hWE6vY3nWkhxPxtIXB0DbSD2ngALqEAADgALlAIAAMoqQATgAlgAdgA5iAAC%2B9hyNAIAoJAGA4AQxBkCAhi0JODoMHwciKSAqnqVpelGaZhAALRiJZ1k6QArvZJCQOQCDySZZnsYgIC6QAJupQX5EoPmQCAnAAI4qQAnupnAlUpuDqeg2AoIlQA https://www.digikey.com/en/products/filter/embedded/microcon... is the link to my search, which i trust hn will abbreviate in a useful way. but lcsc has the ch32v203 in stock for 39¢ in quantity 100 https://www.lcsc.com/product-detail/Microcontroller-Units-MCUs-MPUs-SOCs_WCH-Jiangsu-Qin-Heng-CH32V203G6U6_C5142280.html https://www.lcsc.com/product-detail/Microcontroller-Units-MC... and that has 20k of sram, 64k of flash (presumably nor!), and 24 gpios. that's half the gpios of the ti chip, but i believe my digi-key search linked above was not limited by pin count so maybe the only reason fram costs more is that ti doesn't license the fram patents to chinese companies? it still beggars belief that ti (and microchip, st, etc.) would be spending three dollars a chip on 8k of nor, or even three dollars a chip divided by two layers of profit margin

by crote 2y ago

doubloon 2y ago

Raspberry pi was originally an educational non profit

dfox 2y ago

I suspect that the Synopsys DesignWare SSI macro in RP2040 can in fact be used for R/W PSRAM or FRAM, but the abridged documentation of it in RP2040 datasheet is not sufficient for one to configure it that way.

crote 2y ago
Ooh, good point! I should definitely look into that.

stefan_ 2y ago

What do you mean by USB-C PHY? USB-C is the connector, and you can run USB 1.1/2.0/3.0/3.1 through it, but realistically a RP2040 can not feed even a USB 2.0 PHY.

15155 2y ago
The USB version doesn't directly imply link speed - USB 2.0 devices can be LS, FS, HS. The RP2040 can handily saturate LS/FS links. With PIO or the SPI master and DMA you could absolutely make use of a USB HS PHY.
crote 2y ago
A PHY for the USB PD communication over the CC wires. That makes it possible to negotiate things like Alt Modes for a USB-C connector. DIYing one is surprisingly hard due to the voltages and timing involved.

ChiefNotAClue 2y ago

Well said. I'll add that, as a hobbyist, you'll eventually work on more involved projects and run into those exact limitations.

kragen 2y ago

i'm curious what kinds of applications you've found fram most useful for. it seems like a really cool technology, but the price point is so high that i struggle to understand when you'd use it rather than a combination of sram (or psram) and nand

dragontamer 2y ago
I assume that most people's use of FRAM is when its integrated into TI's MSP430 microcontrollers IE: if FRAM comes free with your MCU, might as well use it and take advantage of its benefits. For example: MSP430FR4132, just picking one such MCU off of Digikey (https://www.digikey.com/en/products/detail/texas-instruments/MSP430FR4132IG56/5067015 https://www.digikey.com/en/products/detail/texas-instruments...) ------ Most of what I know of FRAM comes from TI's marketing pages. https://www.ti.com/document-viewer/lit/html/SSZTA32 https://www.ti.com/document-viewer/lit/html/SSZTA32
- kragen 2y ago
  probably so, but crote was talking about external fram chips the msp430fr4132 you linked costs 160¢ in quantity 35, which is actually considerably cheaper than comparable flash-based chips like the msp430f233 https://www.digikey.com/en/products/detail/texas-instruments/MSP430F233TPMR/1784864 https://www.digikey.com/en/products/detail/texas-instruments... which is 500¢ in quantity 25. so that's maybe one reason people would use fram: evidently it's cheaper than nor? but i'm pretty sure there are μcs with 8k of nor flash that are cheaper than that and in fact cheaper than the price difference. is this pricing policy some sort of loss leader by ti to drive fram adoption? it seems unlikely. does using fram instead of nor make it cheaper for ti to make the chip? surely 8k of nor couldn't account for such a large cost on further investigation, i don't find μcs with 8k of nor flash that are cheaper than that, at least in stock at digi-key and still in production. https://www.digikey.com/en/products/filter/embedded/microcontrollers/685?s=N4IgjCBcpgrLVQGMoDMCGAbAzgUwDQgD2UA2iAEwUDs1ALNSIVbXQBxOUAMbAzLxGbtYvCpwoA2CdQpdxUmYMoKKvcWy4BOLnU51NvOl0bNqXWNvGa6quc2uqx9m7wTPVE9UYpLe5rSYg1IawgWzUYIac4ZFuIDG8noQJgfqG5pyaEgZqhGBcflKZbBIUcfkaYJqcFVyyNTx15Y00DRoUHIR0%2BmCteWASvYFgNll24KODNbB00sMz0p3gC9TVeQsaNRIzm10GRkngUn654GxsRuNg50ZK1xd1NTcZec%2BH1xIX5Zpmmk6UIxkgR8DA64jK4X%2BVFg4VO0PCumYEOocW2BnO4gO4UxvBRcQo3WswMJ7Ex%2Bn0nBkGk0SzKVKUdI6-0UbE0%2BIsIkOZTZuPEHN4tMGIjWyjgRnkYsRop28h49HkAoECr4UO2onGHRk8HUWq5BjgcT8AUNXAChxOqiWFt4Iot4sIfjorhFtDZgVW12Zmmupwe12itxFD3qyVgBMOJTqUpKsFN0W2j2SCd9CcO2m2hyd7B0mXg3oa%2BS4d3MbAGNWusfeFeM5bYsaWIwKNum1GyUrgqx%2BLc0NOmGkTy378w0s040lCMK2sA%2BT2C3SepciY7rNpFVR%2B%2BXEAw6Gpt-Che-44kP%2BL3EilqgMRUI2VoEUxVCmQgs9sosykXMGBWB1Bid1k07lABIbgMBSh0AM2x6AStB6MEuzxAUkT-PAoinDMNpXJ8mo1KoeY1AIqwanUAynJMvJIr%2BdbiDopRKBEZhQYQDFcNeIDZNo%2BbMFIpZLCx0hWE6vY3nWkhxPxtIXB0DbSD2ngALqEAADgALlAIAAMoqQATgAlgAdgA5iAAC%2B9hyNAIAoJAGA4AQxBkCAhi0JODoMHwciKSAqnqVpelGaZhAALRiJZ1k6QArvZJCQOQCDySZZnsYgIC6QAJupQX5EoPmQCAnAAI4qQAnupnAlUpuDqeg2AoIlQA https://www.digikey.com/en/products/filter/embedded/microcon... is the link to my search, which i trust hn will abbreviate in a useful way. but lcsc has the ch32v203 in stock for 39¢ in quantity 100 https://www.lcsc.com/product-detail/Microcontroller-Units-MCUs-MPUs-SOCs_WCH-Jiangsu-Qin-Heng-CH32V203G6U6_C5142280.html https://www.lcsc.com/product-detail/Microcontroller-Units-MC... and that has 20k of sram, 64k of flash (presumably nor!), and 24 gpios. that's half the gpios of the ti chip, but i believe my digi-key search linked above was not limited by pin count so maybe the only reason fram costs more is that ti doesn't license the fram patents to chinese companies? it still beggars belief that ti (and microchip, st, etc.) would be spending three dollars a chip on 8k of nor, or even three dollars a chip divided by two layers of profit margin