The NG Hardware Abstraction Layer

The HAL Concept of the NG

Introduction

To be able to fly the available Controllers with different motor/propeller configurations a NG has a Hardware Abstraction Layer called HAL. The HAL layer can be exchanged and has a simple common API. This allows to support different propeller/motor configurations as well as different actor types (i2c-blc, servo, i2c-servo).

Concept

A NG controller will calculate and output corrections relative to the 3 axis pitch, roll and yaw.

The above corrections output by the choosen controller then gets passed to the Hardware Abstraction Layer, which can be exchanged similar to controllers. The choosen HAL then calculates single actor output values for each actor available and supported in this HAL and passes these values forth to the actor output layer.

Implementation

The HAL API is quite simple. Each HAL consists of a HAL init, input and output function. The HAL's input function gets called before the controller's closed-loop step gets done and the HAL's output function get's called after the closed-loop step.

The HAL has the possibility to modify the controller input data before it runs and it has the ability to alter the controller's output data after it did it's calculations.

This allows HALs to do their transformations of input and output data needed to support specific HAL features.

A HAL's output function essentially receives 4 values from a controller. That's a correction factor for nick, roll and yaw. A fourth value is the current throttle. These four values then get projected onto the choosen motor/propeller/actor configuration.

The implemented HALs

Several HALs are already implemented. Essentially all we needed till now. A HAL is easy to implement and so we have to expect that the number of HALs will grow fast.

The 'none' HAL

The 'blc' HAL

The 'quad' HAL

The 'quadX' HAL

The 'quadR' HAL

The 'Y6' HAL

The 'X8' HAL

The 'X8X' HAL

Configure the HAL

You can configure your NG for different hardware configurations. You do this by choosing the right HAL Hardware Abstraction Layer) for your propeller/motor configuration.

The list of available HALs

The command list hal shows all existing HALs and their current status:

• # list hal
  
  Possible 'HW.HAL' settings:
  
      00  none    The do-nothing HAL (proven)
      01  blc     The BLC test HAL (only for testing purposes)
      02  quad    The 4 rotor Quadcopter HAL (proven)
      03  quadX   The 4 rotor Quadcopter HAL (X-formation) (proven)
      04  quadR   The 4 rotor Quadcopter HAL (reverse) (proven)
      05  Y6      The 6 rotor Y6 Hexakopter Coax HAL (proven)
      06  X8      The 8 rotor X8 Oktocopter Coax HAL (ready for test flights)
      07  X8X     The 8 rotor X8 Oktokopter Coax HAL (X-formation) (only for testing purposes)

Setting a new HAL

When you have decided which HAL to use, you can choose it by setting the global variable HW.HAL:

• # set HW.HAL quad
  
  Activated propeller HAL 'quad'
  Setting 'HW.HAL' to HAL 'quad'

Verifying the current HAL

With the commands show hal and scan actors you can verify that everything works as expected:

• Current HAL: quad
  
      HAL Id:                    2
      HAL Description:           The 4 rotor Quadcopter HAL
      HAL Quality:               proven
  
      Needed number of actors:   4
      Detected number of actors: 0
  
      Motor 1: front
      Motor 2: back
      Motor 3: right
      Motor 4: left
  
  Description:
  
  This is the classical 4 rotor (non-cross) QuadCopter HAL. It allows
  to fly a classical QuadCopter with a front, back, left and right motor.
  
  Current HAL configuration:
  
    HW.HAL     quad                HW abstraction layer
  
  # scan actors
  
  Scanning I2C1 actor bus...
  Scan finished.
  
  Busscan results I2C1 [0x10..0xf6]
  ---------------------------------
  Found device at 0x52
  Found device at 0x54
  Found device at 0x56
  Found device at 0x58
  
  Using actor addresses: 0x52, 0x54, 0x56, 0x58
  Actor state machine will be STARTED in Holger BL-Ctrl mode!
  
  Found actors in current setup: 4
  Needed actors in current HAL:  4