Roof Top Air Handler Unit

Project Description

The project includes the creation of firmware to implement an existing application on a new hardware platform for a Constant Volume Air Handler Unit. This Echelon Lonworks Neuron ‘C’ based device is used to control a heating, cooling and ventilation system for a zone in a commercial building. Various areas of development were involved. The project required the removal of hardware specific references in a large Neuron C application, which were replaced with calls to a device driver. Two device drivers were then created; one for the current hardware, and one for the new hardware. This separation of the hardware specific code allows the company to enhance and modify the application once; knowing that the changes made to the application will be actualized for both types of hardware. This also allows this new hardware platform to be integrated more quickly into other applications. The new hardware platform implemented new functionality that was not part of the original product’s interface specification. Developed and implemented a standard to automatically take advantage of the new hardware’s capability, without changing the interface specification. In addition to the creation of firmware for this product, several hardware modifications were also required as the initial design for the new hardware had some functional errors. Suggested several changes, which were implemented, to allow the unit to function correctly and enhance the detection of invalid inputs.

Skills Required

  • Proficiency in the Neuron ‘C’ language
  • Echelon Lonworks knowledge
  • Real Time Operating System experience
  • Knowledge of environmental controls
  • System architecture knowledge
  • Knowledge of HP-VEE
  • Knowledge of Lonmanager DDE server
  • Electronic circuitry design skills
  • Good organizational skills

Services Used

  • Design, coding, and debugging of Neuron ‘C’ applications
  • Creative implementation of new functionality within the existing device’s framework
  • Developed table based, floating point, sensor linearization mechanism
  • Creation of Product Acceptance and System Integration Test Plans
  • Documenting of software and test procedures
  • Consulting with automated test equipment personnel as to functional test requirements

Project Size

  • Development: 3 man months
  • Testing per customer’s procedures: 1 man month


Manufacturer of environmental controls.