[capnproto] Cap'n'proto on microcontrollers

[David Ondrušek]

Hi Kenton,

I'm developing an IoT device using the ESP8266 wifi-enabled
microcontroller. When connected to wifi it has 48kB free RAM.
Cap'n'proto is useful for my project since message building/reading is a
static process. So it's easy to check if there is enough free memory to
process the message. That's important because while modern microcontroller
toolchains do compile C++ code. C++ exceptions aren't really supported.

What i'm unsure about is if i should also port over the two party RPC
implementation. It would make communication a lot easier. But i don't know
if that's even feasible given the low memory available.

['Kenton Varda' via Cap'n Proto]

Hi David,

I'm not sure, but I suspect you may have a tough time with the RPC
implementation -- and the KJ async framework in general -- in such a
constrained environment. :/

Disabling exceptions should be OK -- everything is designed such that it
should still work (although fatal errors may abort the process). But the
async stuff is pretty malloc-heavy and I don't think it would be easy to
guarantee that memory usage stays under your threshold.

-Kenton

On Thu, Oct 5, 2017 at 12:06 PM, David Ondrušek <

Post by David Ondrušek
Hi Kenton,
I'm developing an IoT device using the ESP8266 wifi-enabled
microcontroller. When connected to wifi it has 48kB free RAM.
Cap'n'proto is useful for my project since message building/reading is a
static process. So it's easy to check if there is enough free memory to
process the message. That's important because while modern microcontroller
toolchains do compile C++ code. C++ exceptions aren't really supported.
What i'm unsure about is if i should also port over the two party RPC
implementation. It would make communication a lot easier. But i don't know
if that's even feasible given the low memory available.
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[Vitaliy Bondarchuk]

imho, Capnproto is too heavy even for successor, dual core ESP32
i can suggest use more lightweight binary flat-serialization protocol, or
don't invent bicycle and use JSON (with RapidJSON library) + JSONRPC 2.0.
and as transport trivial http+WebSocket is enough.

четверг, 5 Пктября 2017 г., 22:06:45 UTC+3 пПльзПватель David OndruÅ¡ek

Post by David Ondrušek
Hi Kenton,
I'm developing an IoT device using the ESP8266 wifi-enabled
microcontroller. When connected to wifi it has 48kB free RAM.
Cap'n'proto is useful for my project since message building/reading is a
static process. So it's easy to check if there is enough free memory to
process the message. That's important because while modern microcontroller
toolchains do compile C++ code. C++ exceptions aren't really supported.
What i'm unsure about is if i should also port over the two party RPC
implementation. It would make communication a lot easier. But i don't know
if that's even feasible given the low memory available.