Difference between revisions of "ALDL Interfaces"

Revision as of 14:02, 6 May 2018

The Elan's ECU can be accessed via the ALDL port for real-time engine monitoring. A suitable electronic interface is required.

Serial (RS232) Interface

USB Interface

Bluetooth Interface

This interface has been designed to provide a robust Bluetooth (wireless) connection. The interface can be used for connecting to the Windows based ElanScan and Android based ElandroidScan software.

Bluetooth device

The Bluetooth interface is designed around the commonly available Roving Networks RN41/42 chipset. The RN41/42 must be pre-programmed with custom setting for e.g. the none standard baud rate of 8192. Communication with the ALDL interface is via the transmit and receive ports.

Device power

Unlike direct (serial or USB) interfaces, which source their power from the host computer, a Bluetooth connection is dependent on the car's battery. When the battery voltage dips during engine starter motor activity, there is a risk that the Bluetooth interface power supply can drop out thereby and losing the Bluetooth connection. A Bluetooth connection takes a significant time to become re-established and may need to be initiated manually. To this end, the power supply is derived from the nominal +12V battery voltage available on the ALDL interface and is suitably sub-regulated with a robust reservoir to guarantee the Bluetooth connection is maintained.

To avoid the risk of battery drain when the car is not in use, the ALDL line is monitored by the sub-regulated power supply circuit and the Bluetooth interface is only powered up when the car's ECU is active, otherwise the current drain is negligible (microamps).

To maintain the Bluetooth link when the engine is switched off, the interface remains active once a Bluetooth connection has been established and does not drop out until the Bluetooth connection is stopped or drops out e.g. controlling device goes outside of the operating range.

Hardware

The Bluetooth interface has been manufactured with a custom designed single-sided printed circuit board (pcb) and this, together with the ALDL plug, is housed in a plastic case. The interface can be discretely plugged into the car's ALDL port and left in-situ if required.

Additional features

The RN41/42 chipset has many additional input/output ports. One of these is configured as an output and may be used to command the Service Mode line to become active to aid setting up the engine Base Timing. Another port is configured as an input to monitor the state of the Service Mode line to be able to confirm that the car is in service mode.