ElanScan USB or Bluetooth?

[Se]

Hi. I have a plan to connect the ALDL to my PC. I have looked at Alan's ALDL page. On his base interface, he used FTDI USB to TTL (correct me if I'm wrong) board and he stated that the Tx / Rx pin should be connected together (I have no idea why here. anyone?) and then connected to the ALDL dataline, with ground of the board to ALDL ground.

I've searched and found this little red board shown here and wonder will it work on the same principle? Anyone have tried?

I've searched a little bit more and found the little blue board shown here as well and it's the same question here. My concern is that it says on the Tx/Rx pin is 3.3v level. Don't know will it work with our ALDL 5v level (correct?)

And what is the best way to get +5V for feeding the blue board. Any thoughts?

Thank you.

[Giniw]

Hello,
As for the connection between the Rx and Tx, it's because the ALDL uses a half duplex protocol (transmission and reception on the same wire). A regular serial line is using two wires, so they must be connected for the contraption to work properly.
As for the serial/usb adapter, one can use a serial/usb adapter from arduino from instance (https://www.arduino.cc/en/Main/USBSerial) which is known to work and is powered directly through the USB cable from the computer (and if you want a standalone arduino you may connect the 12V supply directly to the VCC pin — but I have not tested yet so IT NEEDS CONFIRMATION FROM MORE SKILLED PEOPLE than me)
BUT PLEASE BE CAREFUL: it is apparently a good idea to add a diode (read that thread for further details viewtopic.php?f=34&t=25275&p=319795#p319790)

[Se]

Thanks Giniw. You mean like this?

Any thoughts on the bluetooth board? Will it also works?

Cheers,

[Fredjohn]

Why not just buy the lead from Geoff to run elanscan on your laptop rather than risk burning out your ecu? Just sayin'

[Saltire]

Why not just buy the lead from Geoff to run elanscan on your laptop rather than risk burning out your ecu? Just sayin'

Although a Bluetooth connection would be fantastic. And a version of Elanscan for tablets would be even better

[Se]

I'm looking forward to it as well. There's an app called Torque on OBD2 iirc that can be used on tablet or mobile phone so why not ALDL/Elanscan? I'll try to get there.

For now I checked the 5V and 3.3V TTL logic level and I think they are compatible. But we might need a protection from 5V side if they are not built in the chip already. I didn't see datasheet for the blueboard (what chip do they use) but I will try digging in. Any thoughts?

Why not just buy the lead from Geoff to run elanscan on your laptop rather than risk burning out your ecu? Just sayin'

You reckon Alan was plotting to kill my ecu

Just kiddin' . That's why I asked if it is ok to use or not. 'If it has a risk, how can we prevent it?' sort of thing. Then Giniw said we might be ok just put a diode in. That would have to wait for him to confirm though.

I remembered buying Geoff's cable a long time ago, or may be from his friend who bought it from him and sell it to me. I want to do it myself because it is fun and I want to know more about these stuffs - but with a good safety margin for sure.

[Giniw]

Alas I am afraid I can't confirm because I don't know much in electronics.
(A friend of mine told me GeoffSmith advised to put the diode the wrong way in his post I linked earlier — GeoffSmith would probably confirm?)

[Se]

Thanks Giniw.

I might put USB TTL to 3.3v mode and add a 8k/16k ladder (voltage divider) at the input for protection. see if it works.

[Giniw]

For the record, I just found a parallel discussion about that on another forum:
http://forum.arduino.cc/index.php?topic=409035.0

The general consensus seems to be that the diode should be the other way round indeed, and as even Geoff once said there http://forum.lotuselancentral.com/viewt ... 53#p152753 that the anode should be connected to the ECU and the cathode to the interface, I gather that indeed the drawing there http://forum.arduino.cc/index.php?topic ... msg2815490 is the right one (anode to the ECU and cathode to the interface) and that Geoff made a little typo in his later post there http://forum.lotuselancentral.com/viewt ... 95#p319790.

I am copying the second correct (?) drawing from Se/Hamster7 he posted on the arduino forum in case it disappears:

USB-ALDL Interface R1.png

(I don't think the 10k resistor between the B and A/ground wire has any purpose)

By the way, as far as I understand it, the 4k7 resistor between the FTDI Rx and the ALDL data wire is not mandatory because there is already one in the ECU.


PS: then again, that tends to prove it's probably much safer to ask a safe opto isolated link from Geoff anyway than soldering something when you don't understand it ^^'