Trying to connect via Bluetooth.

General Topics for configuring, operating and tuning the Megajolt. Also see the <a href="http://www.autosportlabs.net/MJLJ_V4_Operation_Guide">Operation Guide</a>

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bobclevenger
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Trying to connect via Bluetooth.

Post by bobclevenger »

I have been trying to get my MJLJ Configurator to connect via Bluetooth for a while now with very little success.
The list of failed attempts can be viewed at http://www.autosportlabs.org/viewtopic. ... 0631#20631

The MJLJ module works just fine. It controls the spark advance of the car very well.
The configurator software works just fine as long as it is connected with a cable.

At the moment I am using a new Lenovo Miix 2 8" tablet running Windows 8.1 and everything worked right off the bat. The tablet sits in a windshield mount when in the car and is very stable and convenient. The cable running to the MJLJ unit is a bit messy, though, and it prevents me from having a charger connected at the same time as the MJLJ unit.

Does anyone have any procedures that actually work to make the MJLJ module communicate with a BT adapter?
...Bob

brentp
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Post by brentp »

If the BT adapter simply exposes a COM port (you can verify in device manager) then it should work, as it behaves just like any serial port, once you configure the app to use that port.

What specific error messages are you seeing?
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bobclevenger
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Post by bobclevenger »

Thanks for getting around to this.

Yes, that is how it is SUPPOSED to work.
My new COM port shows up in device mangler just fine, and I configure the MJLJ software to use that port. That should make things work, right? Actually two new ports show up, but I try both of them (separately of course) and neither one works.

I get the usual time out or failure to open COM port messages. Pretty much the same thing as if the cable were unplugged and no other communications were provided.

It has been so long since I have tried this that I really forget what other messages occur, if any. The BT cards (yes, I have tried two different cards) have just been sitting on my desk. If we are going to look into it, I can hook up the BT board again and start over. Otherwise I am tired of banging my head against a brick wall.

I know that it has been done successfully by others which is what made this so frustrating.

Again, thanks for getting back to me on this.
...Bob

brentp
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Post by brentp »

One thing you could do is remove Megajolt from the equation and just try to communicate between two computers, and ping pong data via a serial terminal. that would establish whether you can basically send data.

Also, on the Megajolt side (assuming you have V4 and later) you will need to set it's baud rate to 38400.
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bobclevenger
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Post by bobclevenger »

Yes, I do have V4.0.2 of the Megajolt software.

Any hints on how to set the baud rate to 38,400?
My BT cards have no place on them to set the BR. I assume that must be done via the COM port using some sort of terminal program. I have both PUTTY and Tera Term available.

Thanks
...Bob

brentp
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Post by brentp »

The bluetooth adapter that interfaces with the Megajolt needs a way to set the baud rate it uses to communicate with the megajolt. The documentation for that adapter should show you how to do that.
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bobclevenger
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Post by bobclevenger »

Yeah, documentation would have been nice.
...Bob

brentp
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Post by brentp »

Can you post a picture of the bluetooth module you're using on the megajolt side? any links to a website where you purchased it?
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bobclevenger
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Post by bobclevenger »

Here are two photos of the two BT cards I have used.


Below is the first one -- it needs to be connected to TTL/RTL level signals.
Image

Below is the second one -- it should accept RS-232 signals directly.
Image


I purchased them both from eBay. They should be pretty generic. Yeah, I know 'should' covers a multitude of sins.
...Bob

brentp
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Post by brentp »

we're familiar with those; we use a variant of that module in the RaceCapture/Pro bluetooth module.

Normally they need to be sent a command to change the standard baud rate. Typically they are set to 9600 baud by default.

There are also two versions of that board - one is called an 'hc-05' which can operate in master or slave mode. These have a specific AT command for setting the baud rate.

The other is called 'hc-06' which has yet a different command for setting the baud rate.

They are visually identical, otherwise. Do you know which variant your module has? Did it come with any docs? Can you link the ebay auction of the seller?

Thanks.

bobclevenger
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Post by bobclevenger »

Making progress, I think.

I shall try to look up the eBay auction, but it has been quite a while.

I'll let you know after I look it up.
...Bob

bobclevenger
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Post by bobclevenger »

Well, the auction data is not on eBay anymore, but the seller has a listing which looks to be the same thing. The data from the listing is:

Features:
•This small size Bluetooth TTL transceiver module allows your target device to both send or receive the TTL data via Bluetooth technology without connecting a serial cable to your computer.
•It's easy to use and completely encapsulated.
•TTL data transparent transfer between a host Bluetooth device.
•Works with any USB Bluetooth adapters.
•Default Baud Rate: 9600,8,1,n.
•Coverage up to 30ft.
•Built in antenna.
•Power input: 3.6V-6VDC(Can not higher than 6V).
•Mini Size

Specification:
•Bluetooth version: V2.0+EDR
•Operating voltage: 3.3V
•Default Baud Rate: 9600,8,1,n.
•Signal coverage: 30ft
•Cable length: 21.5cm
•Item size: 4.3 * 1.6 * 0.7cm
•Item weight: 3g
•Package size: 9 * 3 * 1cm
•Package weight: 8g


I hope this helps.
...Bob

brentp
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Post by brentp »

Hi Bob, I would ask them for documentation on configuring the bluetooth chip.
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bobclevenger
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Post by bobclevenger »

OK, I just did that.
...Bob

Alex B
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Post by Alex B »

But how to connect the BT module to the PC for programming the baud rate? For as far as I can see a COM-port doesn't provide voltage. Can it be done by tapping 5 volts current (and ground) from a USB connection and then get the signal (and ground) from the COM-port? Or are there clever low cost gadgets for sale that I haven't been able to find yet?

Alex

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