Hi everyone, sorry for such a long post, but i have a couple of questions regarding two different ways of connecting multiple devices using a bluetooth module. this is my first topic i'm posting, as I'm looking to piece together an UNO R3 project (possibly using Iteaduino), to connect to multiple devices within my vehicle. I currently have two devices in my car, but with the Arduino it will be 3.
I have a tunable daughterboard for my car's engine management computer, and it utilizes a USB connection, then I have a USB to RS232 converter attached to a 2.5mm jack plug lead that goes to a wideband oxygen sensor controller (the wideband sensor itself is plugged into this controller and is not directly wired to the jack in any way). The 2.5mm jack uses the 3 connections on the 2.5mm jack as TX/RX/GND and the control unit for the o2 sensor has the positive power, so it does not require usb power to be active.
here is a diagram of what I mean. the 2.5mm jack plugs into the control unit, and is broken out into a DB9, which I then have plugged into a RS232-USB converter. This is the recommended method at the time of purchasing the controller unit, however- I have a PL2303X Powered 2.5mm to USB cable on route to my house within the next week or so to bypass the RS232 to USB converter altogether. The only issue that may arise is that a lot of these automotive units are picky with FTDI vs Prolific converters and some have a hard time connecting depending on brand, but here's the diagram anyway.
I have both devices plugged into a mini 4 port hub tucked behind my dashboard, and I have a full size female USB connector mounted next to my audio deck that I plug my laptop into in order to connect to the hub, which in turn connects to both devices. One added note: The o2 sensor connects to the laptop, and via a software tunnel, it relays information to the engine management daughterboard. Within the engine controller's software is the ability to display the readings from the o2 sensor in a small window. Thus sharing the information from the o2 sensor to the engine control module (rather than viewing the information on a separate oxygen reading gauge somewhere else in the vehicle). This allows the software to use the o2 sensor data and automatically tune the fuel maps of the vehicle to fine tune fuel levels under driving conditions without a co-pilot sitting in the passenger seat while modifying maps manually (it's more for tuning idle and highway cruising portions of the map, the high-load portions would be left to be manually input, but that's besides the point). Fact is, these o2 sensor talks to the engine control unit via software, and the engine control unit listens (but does not send data back).
I have been browsing the boards for solutions to other peoples connectivity requirements for projects and found this link to a UART TTL to Serial Bluetooth adapter, which would allow my computer to connect to each device using USB through bluetooth:
http://www.elechouse.com/elechouse/index.php?main_page=product_info&cPath=90_91&products_id=574
I have some scenarios that beg questions before I purchase, because these questions determine quantity of units required to achieve desired results (so it will be free shipping if i have to go the expensive route). Lets pretend I own an arduino already.
Scenario 1
item 1) Bluetooth adapter for o2 sensor ($27.00) - slave
item 2) Bluetooth adapter for engine control daughterboard ($27.00) - slave
item 3) Bluetooth adapter for arduino ($27.00) - slave
item 4) laptop paired with built in BT as master connected to each device, each device has unique bluetooth name.
Scenario 1 guarantees that each device will connect via bluetooth under a different device name.
Scenario 2
item 1) o2 sensor connected via usb to 4-port hub via PL2303 2.5mm to USB cable
item 2) engine control daughterboard connected via usb to 4-port hub using regular USB cable.
item 3) arduino connected via usb to 4-port hub via regular USB cable.
item 4) bluetooth adapter wired onto leads of 4-port hub ($27.00) - slave
item 5) laptop paired with built in BT as master connected to one BT slave device, each item shows up in the device manager as a separate USB device, but would really be connected through same BT module.
Scenario 2 attempts to connect each device using one bluetooth module, sharing the serial bus.
Questions:
A) is scenario 2 possible? It would cost quite a bit less = more money for arduino and other stuffs.
B) would there be speed issues? I read a max of 2mbit/160kbps a second or something like that... not sure if that's enough but I think the only time it would max out is when I'm uploading an entire map or downloading a datalog. But I'm a patient person.
C) Would the single bluetooth device be able to translate the information from 3 different devices attached to the 4port hub, or is it not possible with such a unit - or more importantly, would the laptop be able to handle 3 devices simultaneously?
D) I doubt this is possible given the signal type, but would I be able to wire the 2.5mm jack leads directly into one of these units, or does it have to be converted to a USB signal using the PL2303X cable that I've ordered, or can I go directly from the 2.5mm leads to the board and then through bluetooth? If not, that's fine. I'll just solder a female USB connector pigtail to the bluetooth module. The company that makes the controller offers a fully digital version now that goes from 2.5mm to USB with no RS232 connection in between, so I doubt that i would be able to bypass and go straight to the bluetooth module. This is something I'm pretty sure of, but I'll ask anyways. Maybe this bluetooth module will also convert directly from RS232?
space is an issue, so the less the better. But then again, with 3 tiny adapters I won't have to run wires, so I can shove the boxes wherever I please and have them just connect from anywhere within the cabin under different names.
so essentially:
3 bluetooth units attached to each device with different names??
or
1 bluetooth unit attached to 4port hub with each device attached to the hub??
i know the simple answer is "buy one and try it", but if someone KNOWS i will have to buy 3, then I will get free shipping by buying them altogether, which puts more money into the pot for the rest of the devices/shields i want to buy. If I buy one, and find out it doesn't work, I would then lose out on the free shipping if I have to buy 2 more devices later, and I would then have to pay for shipping on those items- and I don't see anything else I need on the website that sells the bluetooth modules that i could use to buff up my initial purchase to 100 dollars for the single bt module to test. With 3 devices in my cart, if it falls short of 100 bucks- then I can maaaaaybe find something to buff it up with to meet the requirements for free shipping- but with 1 or 2 devices... waste of money!