Controlling LED grids

Basic usage

An LED grid on a BLOCKS device can be controlled via an LEDGrid object, which can be obtained from the Block::getLEDGrid function of a Block—see the Discovering BLOCKS section for details of how to obtain a Block object.

Using an LED grid requires an LEDGrid::Program to operate the LEDs. This program specifies some code to run on the device, and can also provide methods to be called from your application which can comminucate with the code running on the device via a block of shared memory. The code which runs on the device must be specified using The LittleFoot Language, which is described in the corresponding section. However, for a very wide range of applications, the BitmapLEDProgram provided with the BLOCKS SDK is sufficient and you will not need to create your own. Using a BitmapLEDProgram to change the colour of LEDs is demonstated below.

// This should be called when doing the initial configuration of your application.
void setBitmapLEDProgram (Block& block)
if (auto grid = block->getLEDGrid())
grid->setProgram (new BitmapLEDProgram (*grid));
// Once a BitmapLEDProgram is loaded we can use its setLED method to change the
// colour of LEDs on the corresponding device.
void setLED (Block& block, int x, int y, Colour c)
if (auto grid = block->getLEDGrid())
if (auto program = dynamic_cast<BitmapLEDProgram*> (grid->getProgram()))
program->setLED (x, y, c);

Advanced Usage

Using a custom LEDGrid::Program allows more precise control over the operation of the LEDs. The code which will actually execute on the device, returned by your overriden LEDGrid::Program::getLittleFootProgram() function, must be specified in the LittleFoot language.