Pololu Wixel User Manual download pdf (Page 61)

Initially, you will commit your changes to your local repository, but when you are ready to publish them, you should

set up your own repository on GitHub to make them accessible to the community. To do this, sign up for a GitHub

account and fork our repository into a repository on your account. Please do this by clicking the “fork” button at the

top of our repository [http://github.com/pololu/wixel-sdk] so that it will be connected within the GitHub system – this way

we will see your changes and can easily incorporate them into the SDK. After making your fork, you can push all of

the changes from your local repository to GitHub with

git remote add myrepo <GitHub URL>

git push myrepo

where <GitHub URL> is the SSH or HTTP URL shown on your GitHub page.

Finally, you will probably want to post a link to your GitHub repository on the Wixel forum [http://forum.pololu.com/

viewforum.php?f=30]. This will help others find out about it and give you feedback on your contribution.

10.e. USB Configurations Recognized by the Wixel Configuration Software

The Wixel Configuration Utility and the Wixel Command-Line Utility can currently only recognize certain Wixel

apps. If your app is not recognized, then users of your app will not easily be able to reconfigure it after they have

loaded it onto their Wixel (they will have to get their Wixel into bootloader mode manually).

To be recognized, your app must implement a particular USB interface. Specifically, it must implement a USB CDC

ACM virtual COM port with vendor ID 0x1FFB and product ID 0x2200. When the USB host sends a command

to your app that sets the baud rate to 333, your app should enter bootloader mode. Your app should work with the

wixel_serial.inf driver which is installed along with the other Windows software (see Section 3.a). The easiest

way to write an app that meets these requirements is to use the usb_cdc_acm.lib library in the Wixel SDK.

In the future we will add support for other types of USB interfaces if there is a need for it. Please contact us

[http://www.pololu.com/contact] if you would like to use other types of interfaces in your apps.

10.f. Wixel App File Format

For the purpose of loading a compiled program onto a Wixel, the Wixel Configuration Utility and the Wixel

Command-Line Utility (WixelCmd) accept two file formats: Intel HEX (.hex) and Wixel App (.wxl). The Intel HEX

(.hex) file format is an industry standard, and can be produced by most toolchains. The Wixel App (.wxl) file format

is a simple format created by Pololu that includes an Intel HEX file inside it along with important metadata, such as

the names and addresses of user-configurable parameters. The Wixel App file format is designed to be extensible and

easy to generate.

The Wixel App file is plain text: every byte is an ASCII-encoded character. The allowed ASCII codes are 0x20

through 0x7F and also 0x09 (tab), 0xA (new line, “\n”), and 0xD (carriage return, “\r”). The bytes in a Wixel App file

are divided into lines. Line endings can be encoded with any of the following byte sequences: “\r\n” (0xD, 0xA), “\r”

(0xD), or “\n” (0xA).

The first line must be “Pololu Wixel Application - www.pololu.com”. This line explains the purpose of the Wixel

App file. The second line must be “1.0”. This specifies the version number of the file format used in the file.

The third line and all the lines below it are divided into sections. Each section has a one-line header at the top of it that

specifies the name of the section. The header line consists of 6 equals signs (======) followed by a space, followed by

the name of the section. The order of the sections does not matter. The only sections required by the Wixel software

are the cdb and hex sections.

10. Writing Your Own Wixel App Page 61 of 64

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Pololu Wixel User Manual Page 61