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I bought a nodeMCU 8266 and I'm hoping that it can replace my bulkier UNO+WiFi 101.

I'm getting an error when I compile: Error: unknown opcode or format name 'jmp'

I'm using it in void SoftReset() function:

void softReset() {
  delay(1000);
  asm volatile ("  jmp 0");
}

This reset works great with my Uno+101 setup but, for whatever reason, doesn't like the ESP8266. I removed the WiFi101 library and added the ESP8266 WiFi libraries. That has been the only change.

Can you please help me understand why I'm receiving this error?

EDIT: I have read this SO answer but the "syntactical sugar" didn't work for me.

I am also perusing various ESP8266 sites but they are not as well managed as SE/SO and answers are tough to find.

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2 Answers 2

Reset to default
5

The proper way to reset the esp8266 when using the Arduino IDE is to call ESP.reset(). You may need to #include <Esp.h>, but almost all esp8266 headers you include to use any of its functionality will have included it already.

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The ESP8266 is not an Arduino Uno. It talks a completely different language.

It's like you're talking Spanish to a Chinese person. It can't understand you.

If you want to use assembly language then you have to use the assembly language of the chip you are programming for - not the assembly language of a completely different chip.

The assembly language is detailed here: http://techblog.realisaatio.fi/wp-content/uploads/2015/04/xtensalx_overview_handbook.pdf

Bear in mind, though, that jumping to 0 may not reset the device - it may do something nasty.

The only sure-fire way of resetting a chip where you don't really know what is going on inside is to connect a GPIO signal to the RESET pin and use that GPIO to pull RESET low and reset the board that way.

If you want to call address 0 and don't know how to do it in assembly there are ways of arranging it in C using a function pointer:

void (*addressZero)() = 0;

void setup() {
    addressZero(); // Call address 0
}

void loop() {
}

That way it will work on multiple different architectures without having to understand the underlying assembly language. That, of course, is assuming that calling address 0 is a valid way of resetting the board on the target chip.

Browsing through the document I link to above it looks most likely that you would first have to load a register with 0 and then use JX to jump to the address stored in the register (i.e., zero).

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