How to Cross-Compile Bitcoin for Embedded Systems223

Cross-compilation is a technique that allows you to build software for a target platform that is different from the platform you are currently on. This can be useful for building custom firmware for embedded systems, such as home routers or microcontrollers. In this article, we will show you how to cross-compile Bitcoin for an embedded system using the OpenEmbedded build system.

Prerequisites

Before you begin, you will need the following:
A Linux computer with a C compiler and make installed
An OpenEmbedded development environment

Getting the Bitcoin Source Code

The first step is to get the Bitcoin source code. You can do this by cloning the official Bitcoin repository from GitHub:```Bash
git clone /bitcoin/
```

Creating a Cross-Compilation Toolchain

Next, we need to create a cross-compilation toolchain. This is a set of tools that will allow us to compile Bitcoin for our target platform. We can create a cross-compilation toolchain using the OpenEmbedded build system.

First, we need to create a new OpenEmbedded layer. This layer will contain the recipes and configurations needed to build Bitcoin.```Bash
mkdir -p ~/oe-layers/meta-bitcoin
cd ~/oe-layers/meta-bitcoin
```

Next, we need to create a new recipe file for Bitcoin. This file will tell OpenEmbedded how to build Bitcoin.```Bash
nano recipes-bitcoin/bitcoin/
```

In the recipe file, we need to add the following code:```Bash
LICENSE = "GPL-2.0+"
LIC_FILES_CHKSUM = "file://COPYING;md5=21f3639e1a869b888516945f63dba5e7"
SRC_URI = "git:///bitcoin/"
SRC_URI_append = "file://;patchset=\
"
S = "${WORKDIR}/git"
```

This code tells OpenEmbedded where to get the Bitcoin source code, and specifies the license and checksum for the source code.

Next, we need to create a configuration file for Bitcoin. This file will tell OpenEmbedded how to configure Bitcoin.```Bash
nano recipes-bitcoin/bitcoin/
```

In the configuration file, we need to add the following code:```Bash
BB_CXXFLAGS = "-DUSE_UPNP=-DNO_GDB-DDEBUG_LOCKORDER-DNO_ASM"
```

This code tells OpenEmbedded to disable certain features in Bitcoin that are not needed for embedded systems.

Now, we can build the cross-compilation toolchain. To do this, we need to run the following command:```Bash
bitbake -c populate_sdk_ext bitcoin
```

This command will build the cross-compilation toolchain and install it in the ```tmp/deploy/sdk/``` directory.

We can now use the cross-compilation toolchain to compile Bitcoin.

Building Bitcoin

To build Bitcoin, we need to run the following command:```Bash
export PATH=$PATH:/tmp/deploy/sdk/sysroots/x86_64-linux/usr/bin
```
```Bash
make -C ~/bitcoin
```

This command will build Bitcoin for our target platform. The compiled binaries will be located in the ```~/bitcoin/src/``` directory.

Flashing Bitcoin to an Embedded System

Once you have built Bitcoin, you can flash it to an embedded system. The method for doing this will vary depending on the target platform. However, in general, you will need to use a serial cable or a JTAG debugger to connect to the embedded system and flash the Bitcoin firmware.

Conclusion

In this article, we have shown you how to cross-compile Bitcoin for an embedded system using the OpenEmbedded build system. This technique can be used to build custom firmware for a variety of different embedded systems.

2025-02-10

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