5 ms·

I am a big fan of the embassy project and it’s a great example of why async Rust is so great: Because this is possible. It works without a heap, is a really low

I am a big fan of the embassy project and it’s a great example of why async Rust is so great: Because this is possible. It works without a heap, is a really low cost abstraction and you can do stuff concurrently on a single core chip (where you can’t just spawn a new “thread”) and you don’t have the complexity of an RTOS. I believe there is a great future for embassy ahead and it’s so great how far the team has come. I also want to give a shoutout to reqwless (https://github.com/drogue-iot/reqwless https://github.com/drogue-iot/reqwless) which is a HTTP client for embassy-net that even supports HTTPS! Rust embedded was really never actually better then C or C++ but embassy for me is a big reason why I now make my buying decision based on how well I can use Rust on the MCU.

ghotli 9mo ago
If you had to pick a MCU to try this out on, do you have a preference for a devkit to test this with?
- vablings 9mo ago
  RP2040 is really great experience. You can get a debug probe (either buy or make yourself with another RP2040) I cant tell you how awesome it is with minimal setup to get - Full print logging - Option to attach a debugger - cargo r will just flash your code and reset the RP2040
  - inferiorhuman 9mo ago
    probe-rs is amazing. In ARM land it works with pretty much any CMSIS compliant gear, and yeah you get debugging and logging on pretty much anything as a result.
  - progbits 9mo ago
    I wish they had smaller modules with wifi (pico w is too large for many of my usecases). That's the only reason I keep using ESP-C*. It's getting better but the esp-rs tooling has a lot of very rough edges.
    - yonatan8070 9mo ago
      You've got boards like the Seeed Studio Xiao with an RP2040, that board is absolutely tiny!
      - progbits 9mo ago
        The 2040/2350 ones don't have wireless radio.
        yonatan8070 9mo ago
        Oh.. my brain completely skipped "with wifi" in your comment, my bad.
        progbits 9mo ago
        You had me excited for a second :)
    - the__alchemist 9mo ago
      Same. Non-Espressif manufacturers have been sleeping on Wi-Fi capability. Nordic now has a chip, but I haven't tried it. I have been using an Esp running Esp-Hosted, connected to the main MCU over SPI.
    - unnamedd 9mo ago
      It is a little bit complicated to start and understand how the series ESP-S* works, but as soon you do, everything gets better. It does have Wi-Fi and Bluetooth capabilities and also can be very small. A good example are the Adafruit Qt Py series. I am currently working with the Adafruit Qt Py (ESP-S2) and I am in love to that board. This one, doesn’t have Bluetooth, but the S3 does. Because of the Xtensa, you need to use a special fork of Rust maintained by Espressif, but worth a try.
- idan 9mo ago
  Also espressif RISC V mcu's like the ESP32-C3 and -C6 are fantastic. Some Nordic MCUs are easy too, specifically nrf52840. Have fun!
  - apitman 9mo ago
    Just got my first esp32-c6 and really excited to start playing with it. The p4 looks like a beast and want to try that out eventually as well. Feels good to be back hacking on embedded again.
  - ecalifornica 9mo ago
    I'll second this, Embassy on the ESP32-c6 is great.
- inferiorhuman 9mo ago
  STM is popular because their lineup is cheap, offers a lot of features, and the documentation is readily available. The flip side is that their errata is lengthy, the Rust HAL is complex to support lots of different designs under the same product names, the documentation from STM is poorly organized and spread out over a zillion different documents, and Mac compatibility needs a gigantic asterisk. You can also get a BlackPill (get the F411 version with 8MB flash) off of AliExpress for $0.99 from WeAct's official store. Unlike STM's own dev boards (Nucleo) you'll need a separate debug probe. Nucleos that'll give you a lot of breathing room can be had for $10-15. RP is also cheap and has that pretty sweet programmable GPIO and documentation that everyone seems to love. Adafruit has an RP2040 Feather for $12, RP2350 for $15, or with an ESP32-C6 (RISC-V) for $15. NXP has chips with similarly programmable GPIO but they're not well supported by Rust. The RP's PIO stuff is bonkers and potentially very interesting if you wanted to make random protocol dongles. VGA out? Why not? Nordic stuff looks pretty sweet (and their Bluetooth support seems well loved) but is generally a bit expensive. Dev boards are available from micro:bit and Adafruit, among others. I've been working on a HAL for an older Atmel SoC and absolutely loved the documentation. But Atmel stuff is expensive. Quality of the Chinese clones is iffy. I set myself back a bit by bricking my one board but am hoping to have a beta release in a month or so. More recent Atmel/Microchip stuff (D21, D51, E51) has a HAL that the Embassy folks seem to have overlooked. You can get them on Adafruit boards at varying price points. Or just pick something unsupported and start writing a HAL. It's a great way to get up close and personal with how everything fits together. The one thing I wouldn't do is get some high end thing to start with. Teensy's (NXP i.MXRT) pack a lot of punch but even their native Arduino libs don't really let you exploit the power. STM's H7 series as well, they're way too complex to use as a learning tool even if they are fairly cheap.
  - 5d41402abc4b 9mo ago
    > The flip side is that their errata is lengthy Just like security bugs, lengthy errata doesn't mean anything. A popular MCU will have bigger errata sheet because it gets more eyes on it. >documentation from STM is poorly organized and spread out over a zillion different documents The spreading out over multiple documents is good organization. You don't want to combine your datasheet, reference manual and appnotes into one.
- baby_souffle 9mo ago
  Nordic nrf series of chips are ubiquitous, cheap, really well documented and have very good support for the Bluetooth side of things in embassy. If you don't need any of the wireless radio stuff, I think the raspberry pi microcontroller family is also ridiculously well supported in rust and it's possible to get one of the newer raspberry pi microcontroller is complete with ethernet and several megs of flash for not even 10 bucks.
cat-whisperer 9mo ago
I agree. the type safety that it brings to the HAL. it's a like cushion for people entering this space. never understood what a watchdog is tho...
- VorpalWay 9mo ago
  A watchdog is a piece of hardware that will automatically restart the chip if it detects the code as being stuck. The way it detects this is that you have to poke a register of the watchdog every so often, and if the register hasn't been poked for a certain timeout (usually configurable), the chip is restarted. Watchdogs exist on MCUs but also on some "proper" computers. The Raspberry Pi has one for example.
  - 5d41402abc4b 9mo ago
    >Watchdogs exist on MCUs but also on some "proper" computers All modern computers have watchdog. You can check your logs `journalctl -b | grep watchdog` https://access.redhat.com/articles/7129255 https://access.redhat.com/articles/7129255
    - LtdJorge 9mo ago
      Yes, but those are done in software
      - p_l 9mo ago
        There's generally at least one watchdog device available in most PCs delivered in last decade, but it's not always utilized. Essentially at one point an intel southbridge integrated a basic watchdog on all models, and it started to just... be included. So these days you can find a variation on the TCO timer watchdog in most PCs, even if the exact implementation varies so we now have a bunch of drivers for the different variants.
        VorpalWay 9mo ago
        Linux doesn't see one on my Ryzen 5600X desktop at least. My Intel Skylake Thinkpad does seem to have two though (iTCO as well as INT3F0D, not sure what that is, but if I interpret the files under /sys correctly it belongs to the LPC/eSPI controller PCIe device, while the TCO watchdog is found under the SMBus PCIe device). In both cases they do have software watchdogs (NMI based) which relies on a hardware timer triggering an NMI in the kernel. But that relies on the NMI handler still working, which is not as good as a real HW watchdog.

ghotli 9mo ago

If you had to pick a MCU to try this out on, do you have a preference for a devkit to test this with?

vablings 9mo ago
RP2040 is really great experience. You can get a debug probe (either buy or make yourself with another RP2040) I cant tell you how awesome it is with minimal setup to get - Full print logging - Option to attach a debugger - cargo r will just flash your code and reset the RP2040
- inferiorhuman 9mo ago
  probe-rs is amazing. In ARM land it works with pretty much any CMSIS compliant gear, and yeah you get debugging and logging on pretty much anything as a result.
- progbits 9mo ago
  I wish they had smaller modules with wifi (pico w is too large for many of my usecases). That's the only reason I keep using ESP-C*. It's getting better but the esp-rs tooling has a lot of very rough edges.
  - yonatan8070 9mo ago
    You've got boards like the Seeed Studio Xiao with an RP2040, that board is absolutely tiny!
    - progbits 9mo ago
      The 2040/2350 ones don't have wireless radio.
      - yonatan8070 9mo ago
        Oh.. my brain completely skipped "with wifi" in your comment, my bad.
        progbits 9mo ago
        You had me excited for a second :)
  - the__alchemist 9mo ago
    Same. Non-Espressif manufacturers have been sleeping on Wi-Fi capability. Nordic now has a chip, but I haven't tried it. I have been using an Esp running Esp-Hosted, connected to the main MCU over SPI.
  - unnamedd 9mo ago
    It is a little bit complicated to start and understand how the series ESP-S* works, but as soon you do, everything gets better. It does have Wi-Fi and Bluetooth capabilities and also can be very small. A good example are the Adafruit Qt Py series. I am currently working with the Adafruit Qt Py (ESP-S2) and I am in love to that board. This one, doesn’t have Bluetooth, but the S3 does. Because of the Xtensa, you need to use a special fork of Rust maintained by Espressif, but worth a try.
idan 9mo ago
Also espressif RISC V mcu's like the ESP32-C3 and -C6 are fantastic. Some Nordic MCUs are easy too, specifically nrf52840. Have fun!
- apitman 9mo ago
  Just got my first esp32-c6 and really excited to start playing with it. The p4 looks like a beast and want to try that out eventually as well. Feels good to be back hacking on embedded again.
- ecalifornica 9mo ago
  I'll second this, Embassy on the ESP32-c6 is great.
inferiorhuman 9mo ago
STM is popular because their lineup is cheap, offers a lot of features, and the documentation is readily available. The flip side is that their errata is lengthy, the Rust HAL is complex to support lots of different designs under the same product names, the documentation from STM is poorly organized and spread out over a zillion different documents, and Mac compatibility needs a gigantic asterisk. You can also get a BlackPill (get the F411 version with 8MB flash) off of AliExpress for $0.99 from WeAct's official store. Unlike STM's own dev boards (Nucleo) you'll need a separate debug probe. Nucleos that'll give you a lot of breathing room can be had for $10-15. RP is also cheap and has that pretty sweet programmable GPIO and documentation that everyone seems to love. Adafruit has an RP2040 Feather for $12, RP2350 for $15, or with an ESP32-C6 (RISC-V) for $15. NXP has chips with similarly programmable GPIO but they're not well supported by Rust. The RP's PIO stuff is bonkers and potentially very interesting if you wanted to make random protocol dongles. VGA out? Why not? Nordic stuff looks pretty sweet (and their Bluetooth support seems well loved) but is generally a bit expensive. Dev boards are available from micro:bit and Adafruit, among others. I've been working on a HAL for an older Atmel SoC and absolutely loved the documentation. But Atmel stuff is expensive. Quality of the Chinese clones is iffy. I set myself back a bit by bricking my one board but am hoping to have a beta release in a month or so. More recent Atmel/Microchip stuff (D21, D51, E51) has a HAL that the Embassy folks seem to have overlooked. You can get them on Adafruit boards at varying price points. Or just pick something unsupported and start writing a HAL. It's a great way to get up close and personal with how everything fits together. The one thing I wouldn't do is get some high end thing to start with. Teensy's (NXP i.MXRT) pack a lot of punch but even their native Arduino libs don't really let you exploit the power. STM's H7 series as well, they're way too complex to use as a learning tool even if they are fairly cheap.
- 5d41402abc4b 9mo ago
  > The flip side is that their errata is lengthy Just like security bugs, lengthy errata doesn't mean anything. A popular MCU will have bigger errata sheet because it gets more eyes on it. >documentation from STM is poorly organized and spread out over a zillion different documents The spreading out over multiple documents is good organization. You don't want to combine your datasheet, reference manual and appnotes into one.
baby_souffle 9mo ago
Nordic nrf series of chips are ubiquitous, cheap, really well documented and have very good support for the Bluetooth side of things in embassy. If you don't need any of the wireless radio stuff, I think the raspberry pi microcontroller family is also ridiculously well supported in rust and it's possible to get one of the newer raspberry pi microcontroller is complete with ethernet and several megs of flash for not even 10 bucks.

cat-whisperer 9mo ago

I agree. the type safety that it brings to the HAL. it's a like cushion for people entering this space. never understood what a watchdog is tho...

VorpalWay 9mo ago
A watchdog is a piece of hardware that will automatically restart the chip if it detects the code as being stuck. The way it detects this is that you have to poke a register of the watchdog every so often, and if the register hasn't been poked for a certain timeout (usually configurable), the chip is restarted. Watchdogs exist on MCUs but also on some "proper" computers. The Raspberry Pi has one for example.
- 5d41402abc4b 9mo ago
  >Watchdogs exist on MCUs but also on some "proper" computers All modern computers have watchdog. You can check your logs `journalctl -b | grep watchdog` https://access.redhat.com/articles/7129255 https://access.redhat.com/articles/7129255
  - LtdJorge 9mo ago
    Yes, but those are done in software
    - p_l 9mo ago
      There's generally at least one watchdog device available in most PCs delivered in last decade, but it's not always utilized. Essentially at one point an intel southbridge integrated a basic watchdog on all models, and it started to just... be included. So these days you can find a variation on the TCO timer watchdog in most PCs, even if the exact implementation varies so we now have a bunch of drivers for the different variants.
      - VorpalWay 9mo ago
        Linux doesn't see one on my Ryzen 5600X desktop at least. My Intel Skylake Thinkpad does seem to have two though (iTCO as well as INT3F0D, not sure what that is, but if I interpret the files under /sys correctly it belongs to the LPC/eSPI controller PCIe device, while the TCO watchdog is found under the SMBus PCIe device). In both cases they do have software watchdogs (NMI based) which relies on a hardware timer triggering an NMI in the kernel. But that relies on the NMI handler still working, which is not as good as a real HW watchdog.