flak monkey
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| posted on 1/9/09 at 07:43 PM |
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Can I split an RS232 Cable?
Odd question, maybe....
I would like to have my ECU connected ot my Aim dash as it has the capabilities to communicate with megasquirt using the serial (RS232) port just by
connecting the TX and RX cables.
By question is, can I have both my dash and my laptop connected at the same time so I can keep an eye on boost pressure and all the other variables
real time from the ECU?
David
Sera
http://www.motosera.com
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RichardK
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| posted on 1/9/09 at 07:49 PM |
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I wouldn't have thought so, what about one of the usb to serial converters so you have 2 com ports? Would that work?
Cheers
Rich
Gallery updated 11/01/2011
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stevebubs
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| posted on 1/9/09 at 07:50 PM |
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not unless your AIM dash has pass-through capability
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flak monkey
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| posted on 1/9/09 at 07:54 PM |
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So connecting 2 cables each to the TX and RX at the megasquirt end and then one set to the laptop and one to the dash isnt going to work then?
I also have to figure if you connect TX-TX and RX-RX or TX-RX, RX-TX as the aim manual is rather vague.
Sera
http://www.motosera.com
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MikeRJ
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| posted on 1/9/09 at 08:12 PM |
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quote:
Originally posted by flak monkey
So connecting 2 cables each to the TX and RX at the megasquirt end and then one set to the laptop and one to the dash isnt going to work
then?
No, since you will have two transmitters (dash and laptop) connected together, so they will conflict.
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mark chandler
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| posted on 1/9/09 at 08:27 PM |
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I just did what was suggested above, really cheap USB to serial dongle and native serial port, just displayed two dashes on my laptop
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flak monkey
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| posted on 1/9/09 at 08:35 PM |
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quote:
Originally posted by mark chandler
I just did what was suggested above, really cheap USB to serial dongle and native serial port, just displayed two dashes on my laptop
Hows that work then?
There is a serial port on the megasquirt which i normally plug a USB to serial adaptor into anyway, where the other bits connect?
Sera
http://www.motosera.com
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blakep82
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| posted on 1/9/09 at 08:54 PM |
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quote:
Originally posted by mark chandler
I just did what was suggested above, really cheap USB to serial dongle and native serial port, just displayed two dashes on my laptop
hmm, i see what you mean, but the megasquirt (which only has one serial port on it?) presumably has to be plugged into the digidash and laptop at the
same time, so i don't think it can work
the only way forward i can think of is if you can get any digi dash type software that can go on the laptop to show the info you need? contact the
digi dash manufacturer perhaps?
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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GregSL75
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| posted on 1/9/09 at 09:04 PM |
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Might work if the digidash doesn't need to use the transmit line. Split the cable and don't connect the Tx.
IIRC megasquirt is permanently putting out the data on the serial port, so depending on how the digidash works it may not need the Tx.
2.0 XE on GSXR TBs and Megasquirt
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Doofus
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| posted on 1/9/09 at 09:11 PM |
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It could be done,
Wire the transmit from MS to the RX on the dash and PC
Since it's easier to re-write the Megatune software wire the TX from the Dash to the RX on the MS and get the dash to send the request char.
You'd need at alter Megatune to receive the reply data without sending the request, but I think it's open source isn't it?
[Edited on 1/9/09 by Doofus]
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flak monkey
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| posted on 1/9/09 at 09:25 PM |
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quote:
Originally posted by Doofus
It could be done,
Wire the transmit from MS to the RX on the dash and PC
Since it's easier to re-write the Megatune software wire the TX from the Dash to the RX on the MS and get the dash to send the request char.
You'd need at alter Megatune to receive the reply data without sending the request, but I think it's open source isn't it?
I like your thinking, but coding is well over my head I am afraid 
Sera
http://www.motosera.com
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Dale
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| posted on 1/9/09 at 10:57 PM |
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You may be able to do it.
It would be easy to do if you only wanted to monitor on one or the other but if you want both to have transmit capability you may be able to get by by
putting a signal diode on both of the transmit lines - one on the dash transmit and one othe laptops. This way the signal will not corrupt the others
signal.
Also depends on weather they are using control signals or just xon/xoff if they are both using just rx tx and ground you might just get away with
it.
Dale
rs232 is suposed to use + and - signals but most get by with 0 and +
Thanks
Dale
my 14 and11 year old boys 22
and 19 now want to drive but have to be 25 before insurance will allow. Finally on the road
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MikeRJ
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| posted on 2/9/09 at 09:29 AM |
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quote:
Originally posted by Dale
You may be able to do it.
It would be easy to do if you only wanted to monitor on one or the other but if you want both to have transmit capability you may be able to get by by
putting a signal diode on both of the transmit lines - one on the dash transmit and one othe laptops. This way the signal will not corrupt the others
signal.
Diode ORing the transmit lines will prevent the transmitter outputs being loaded by conflicting logic states, but if both transmit at the same time
the data will still be corrupted.
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ss1turbo
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| posted on 4/10/09 at 10:09 AM |
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You've got two masters (laptop/digiview), and one slave (MS) - and you can guarantee they'll want different info...so sadly no.
I've used 3 devices on an RS232 line before, but one was a "sniffer" just to see what was going on.
A possibility is a multiplexer, so it only allows one request to the slave (MS) at a time - but beware of timeout issues as if one is waiting its
turn, the other might timeout. The other trick is going to know when the MUX needs to switch over..
Long live RWD...
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