VHDL is a Hardware Description Language. It is used to describe the behaviour and structure of a programmable logic chip, such as a CPLD or a FPGA.

It is similar to Verilog, which is mainly used in the USA, whereas VHDL is more common in Europe.

When speed is essential, a protocol can be implemented in such a component, rather than by software running on a MCU.

VHDL can be unit tested to guarantee behaviour, just like C/C++ code. There are also comprehensive simulation environments that can be used to validate timing and performance.

Bluefruit was recently involved in helping developers gain TDD awareness with VHDL, as one of our developers added VHDL support to cyber-dojo, a tool we regularly used to practice our coding skills.