'File import callback not supported on truffle migrate

I have a truffle project with the following contract (elided) that I'm running with truffle migrate:

    1 pragma solidity >=0.6.0;
    2
    3 // implements the ERC721 standard
    4 import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
    5 // keeps track of the number of tokens issued
    6 import "@openzeppelin/contracts/utils/Counters.sol";
    7 import "@openzeppelin/contracts/access/Ownable.sol";

But I'm getting the following error:

> Compiling ./contracts/NFT.sol

> Compilation warnings encountered:

    Warning: SPDX license identifier not provided in source file. Before publishing, consider adding a comment containing "SPDX-License-Identifier: <SPDX-License>" to each source file. Use "SPDX-License-Identifier: UNLICENSED" for non-open-source code. Please see https://spdx.org for more information.
--> project:/contracts/Creation.sol


ParserError: Source "@openzeppelin/contracts/token/ERC721/ERC721.sol" not found: File import callback not supported
 --> project:/contracts/NFT.sol:6:1:
  |
6 | import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

,ParserError: Source "@openzeppelin/contracts/utils/Counters.sol" not found: File import callback not supported
 --> project:/contracts/NFT.sol:8:1:
  |
8 | import "@openzeppelin/contracts/utils/Counters.sol";
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

,ParserError: Source "@openzeppelin/contracts/access/Ownable.sol" not found: File import callback not supported
 --> project:/contracts/NFT.sol:9:1:
  |
9 | import "@openzeppelin/contracts/access/Ownable.sol";
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Compilation failed. See above.
Truffle v5.4.0 (core: 5.4.0)
Node v14.15.5

How to fix this error?

ethereumsoliditytrufflearduinobluetoothembeddedhc-05arduino-nano


Solution 1:[1]

Even though my contract works I had the same error... I just changed:

import "@openzeppelin/contracts/utils/Counters.sol";

To a more explicit form:

import "../node_modules/@openzeppelin/contracts/utils/Counters.sol";

and bypass those red squiggles.

Solution 2:[2]

Have you run the following commands

$ npm init
$ npm i -s @openzeppelin/contracts

Solution 3:[3]

I saw a lot of videos the result of all of them is: the two modules are automatically connected to each other when power is on. but mine is not!

This confuses me, I can't see any command that will let you initiate connection. My guess is that AT+BIND is a command for trusting. However AT+CMODE is explained as:

Param1: Connection mode: 0 -> Connect the module to the specified Bluetooth address. (Bluetooth address can be specified by the binding command)

In this case, I would send AT+BIND first rather than setting CMODE.

If we have a look at HC-05 AT command list, we can see that there are other commands that are used to establish classical Bluetooth connection. I would do the following in order:

  1. AT+PAIR=MAC
  2. AT+BIND=MAC
  3. AT+LINK=MAC

I would also check the status via AT+STATE?.

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Antoine
Solution 2 Kundan
Solution 3 Mr. Panda

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