Sean Hegarty has been in touch about a new HAT-format board that he and his company (CNC Design Ltd) have released for the Raspberry Pi. It allows clean, fast and accurate pulses to be created using simple ASCII commands. This is especially useful for “hardware designs where a variable frequency pulse is needed, but one that is the most popular is for driving stepper/servo motors that use pulse and direction lines”. It has an on-board Arm Cortex M4 processor running at 100MHz and dedicated direct digital synthesizer (DDS) pulse generators with 0.004Hz resolution for each channel. The HAT stack is capable of up to 4 individual pulse train outputs and also has a bunch of other features that you can read about here. The full package is £55+VAT and you can get the boards from their website.