PiXCLe for ARM Cortex-M3 series

27-Nov-2012: Preliminary information, subject to change.

PiXCLe is a very capable subset of the PiXCL language, and has around 130 commands and operators. You use it to create the app code that defines the user interface and the processing caused by user touch and I/O events.

The app code created is not just a static set of load bitmap commands or complex and obscure language constructs: it simply defines a logical set of user interface items (typically, backgrounds and button or touch regions set at screen coordinates) that generate user events, and the handler code that executes what that event requires. The code itself is easy to read and largely self-documenting. Comments use the familiar C style line ( // comment ) and block style ( /* comment */ ).

PiXCLe is closely integrated with chibiOS 2.4 , an Open Source, multi-threading, interrupt-driven real time operating system (RTOS). We added our own proprietary device drivers and other extensions such as the graphics and I/O libraries.

The PiXCLe language includes the following that you use to create your app code:

File and Directory create, exist, move, copy and delete operations are supported. File size and total / free disk space commands are (probably) available. You can also read and write application INI-style files. On the Decaf boards, these commands refer to the SD card FAT file system and would eventually be called by the disk I/O functions in chibiOS. About 30 commands.

All the commonly used string handling functions are supported. 26 commands.

PiXCLe supports floating point as well as integer variables, plus a set of standard math library functions. The four standard math operations plus modulus are provided in command syntax. About 30 commands. It's uncertain at present if all the standard math library commands will be supportable given the Decaf board resources.

Time functions provide get and set system time, get the current time zone setting, and return a usable time string to programs. They can also be used for scheduling operations such as running other app codes at specific times.

The Decaf boards contain a clock chip that stores and updates the time, so long as the board battery is present, including when the board is un-powered. One time setting is available, with no difference between Local and System as in Windows. At least 3 commands.

PiXCLe supports the unstructured If..Then and Goto commands, plus the structured If...Else...Endif syntax. Thirty-two levels of embedded If...Else...Endif structures are supported. Up to Thirty-two levels of embedded structured For-Next and While-EndWhile loops are available. It is also possible to construct Do-While and Do-Until operations with the labels and Goto statements. For integer variables, the Switch-Case-EndSwitch structure is provided. About 8 commands.

PiXCLe includes a comprehensive set of commands to draw lines, rectangles, circles and ellipses in various colors and pen sizes. There are also polygon flood and fill functions. About 30 commands.

PiXCLe can load and display from the SD card BMP RGB34 image files, and the PiXCL PXI RGB565 open format that can be displayed directly. PiXCL 10.3/11.0 include commands and a sample app that imports any of 15 common image file formats, and export them to PXI format. PXI images can be imported and saved to any supported format.

PiXCLe includes support for simple communications using the serial ports COM1 – COM2. This support is designed to enable devices such as digitizing pads, GPS devices and tables that output coordinate data strings, and accept control commands.

The Decaf boards have analog and digital I/O connections, and there is a set of commands that directly support them to set parameters and get current values. Inputs generally are automatically monitored by threads that issue an interrupt when the parameters change enough to cause an input event. Around 10 commands.

The PiXCLe command set can be extended with custom commands developed by third parties. In the Windows version of PiXCL, these are created in a DLL. In PiXCLe , an extension command file (extension .PLL, equivalent to a DLL) is created with the optional PiXCLe Decaf™ Developers Kit.

In summary, a .PLL extension command set is stored on the Decaf™ board's SD card. and loaded by the Register command. In general, a developer creating an extension command library will implement both the DLL and PLL files, with mostly the same internal code. This duality is preferred (but not essential) as it allows the extensions to be tested in the Windows simulation phase.

It's also important to understand what the RTOS and PiXCLe are not. chibiOS 2.4 is not Windows and does not attempt to create a multi-tasking windowing user experience on a small touch screen. Neither is it MS-DOS though it does provide a FAT file system on the SD Card. What the RTOS and PiXCLe together provide is a device with a familiar file system, and the easy-to-learn tool to quickly create working applications with an attractive user interface on the touch screen. In fact, the specifics of the operating system itself are irrelevent, and the app programmer/user does not need to interact with it in any direct low level way.

PiXCL 10.4/11.0 along with the PiXCL Code Studio is included with all boards. Many of the utilities that are used during PiXCLe app development are written in PiXCL itself, and all utility app source is provided.