That pin layout looks fine to me, assuming the Axim pinout is correct for your model. I believe the MAX232 chip actually converts the 5v signals used with the rest of the circuit into 10V (maybe +/-?) signals, for use in the serial cable. I think the idea behind this is that a larger difference in voltage will create a more reliable reproduction of the transmitted signal at the receiving end.
David
Palm Computer?
Moderators: JeffC, rdoherty, stieg, brentp
PINS/MAX232
Uh-oh. Don't like the sound of that. If the Axim RX shows 3.3v-5v, that seems like trouble to me. Definitely don't want to fry it. Might have to start looking for a good deal on a Bluetooth serial adapter again. And I thought I had this licked. Back to the drawing board, good thing I haven't finished that cable.
Jack
Jack
Jax2A
Wouldnt worry
I wouldn't worry about that, I may be wrong about the 10V anyway.... but the thing to remember is that the digital on/off signals will be happening so quickly at your serial ports that you can't measure the voltage (at least with a multimeter anyway). All you need is a bit sequence of 001 and you'll get 10/3=3.3V presumably? Anyway, I know for sure that when I first wired up my cable I got the Rx/Tx pins connected the wrong way round but there was no smoke coming from the ipaq!
Also if you buy a bluetooth-serial adaptor, this wouldn't work with the program. It's designed to give a serial output and the pocket c language does not support bluetooth.
HTH
David
Also if you buy a bluetooth-serial adaptor, this wouldn't work with the program. It's designed to give a serial output and the pocket c language does not support bluetooth.
HTH
David
Serial Voltages
David, Ok I got my cable finished this past weekend, but I'm not satified with my research enough to try it yet. About half my sources agree with you and say it won't hurt my Axim and about half say it will fry. Problem is I'm not comfortable with 50/50 odds. So maybe you can help by explain this comment:
"All you need is a bit sequence of 001 and you'll get 10/3=3.3V presumably?"
I don't know what the bit sequence of 001 means.
10 (volt signal) / 3 = 3.3v
How do you get from 001 to the 3 you divided by? I've got a feeling if I understood this my comfort level would go up. I've got a degree in mechanical engineering but computer language and serial communication is Greek to me. Thanks,
Jack
"All you need is a bit sequence of 001 and you'll get 10/3=3.3V presumably?"
I don't know what the bit sequence of 001 means.
10 (volt signal) / 3 = 3.3v
How do you get from 001 to the 3 you divided by? I've got a feeling if I understood this my comfort level would go up. I've got a degree in mechanical engineering but computer language and serial communication is Greek to me. Thanks,
Jack
Jax2A
bit sequence
The fact is, when you are sending or receiving data out of the tx/rx pins, it happens really really really fast! just a load of 0's and 1's flying down the cable.
So, if a '0' = 0V, and a '1'= 10V, if you get an average of twice as many 'zeros' as 'ones' you'll end up with one third of the 10V (which is where the 3.3V).
There's no way your multimeter will react fast enough (well it could, but you wouldn't be able to see it!) to the string of 0's and 1's going down the wire, so it just sees the 'average' voltage in the wire which would be 3.3V in this case.
So, on the TX and RX pins you could really be getting any voltage between 0-10V I suppose, depending on the bit pattern that flows out at the particular time. The GND pin should stay at a constant voltage, however, (most probably 0V, but not that sure). If this is fluctuating I wouldn't risk it, otherwise I think you'll be fine. As I said, I connected my TX/RX pins the wrong way round once by accident, but no harm done!
Good luck with it
David
So, if a '0' = 0V, and a '1'= 10V, if you get an average of twice as many 'zeros' as 'ones' you'll end up with one third of the 10V (which is where the 3.3V).
There's no way your multimeter will react fast enough (well it could, but you wouldn't be able to see it!) to the string of 0's and 1's going down the wire, so it just sees the 'average' voltage in the wire which would be 3.3V in this case.
So, on the TX and RX pins you could really be getting any voltage between 0-10V I suppose, depending on the bit pattern that flows out at the particular time. The GND pin should stay at a constant voltage, however, (most probably 0V, but not that sure). If this is fluctuating I wouldn't risk it, otherwise I think you'll be fine. As I said, I connected my TX/RX pins the wrong way round once by accident, but no harm done!
Good luck with it
David
Got A New Plan
David, Talked with several people with experience in this stuff. Many agree with you but one guy said there's a easy solution. He suggested adding a 3.5mm stero type jack to the box and tap into the signal on the other side of the MAX232 chip. This would give me two ports. One boosted by the chip for standard RS232 communication through the DB9 port and then a non-boosted signal through the 3.5mm jack to the Axim x50v. Seems like the best/safest path. Now I've got to add the jack and build a new cable. Small set back, but at least I've got a plan that I'm comfortable with risking my Axim on. Thanks for you input and work. Can't wait to try out your program on my Axim for real. Later,
Jack
Jack
Jax2A
-
strikermk2
- Posts: 0
- Joined: Thu Aug 12, 2004 5:08 pm
ipaq to serial lead.
Hi all .THis is what i have been waiting for. DH154 do you think this lead would be suitable for connecting my ipaq 3970 to the megejolt.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 86148&rd=1
I look at you web site and followed the link for the pin out info but it all looks a little delicate for my welding, sorry i mean soldering skills. If this lead would do the job with modification that would be great.Thanks for all the info.Bryan
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 86148&rd=1
I look at you web site and followed the link for the pin out info but it all looks a little delicate for my welding, sorry i mean soldering skills. If this lead would do the job with modification that would be great.Thanks for all the info.Bryan
palm things
Jack, that sounds like a very good idea, should certainly be safer if you're not sure about the wiring to your axim. It'll also be a easier to connect the wire for tuning than a standard db9, let me know how you get on!
Bryan, that lead looks fine, it's just like the one I bought. The only modification that you <i>might</i> have to make is swap the tx/rx wires so they match the pin out info on my web site. Best way to check this will be with a multimeter once you've bought the lead. Don't worry about the soldering, you can just cut the lead in the middle and join it there if you're not too confident. good luck!
david
Bryan, that lead looks fine, it's just like the one I bought. The only modification that you <i>might</i> have to make is swap the tx/rx wires so they match the pin out info on my web site. Best way to check this will be with a multimeter once you've bought the lead. Don't worry about the soldering, you can just cut the lead in the middle and join it there if you're not too confident. good luck!
david
Extra "serial" port
David, got my extra 3.5mm "serial" jack installed on the board last night and my new cable made. Just need to modify the enclosure now for the new port so I can close it all back up. Do you know how reslient the chips are? I decided to remove the main chip before tapping the new port and bent up a few of the legs pretty bad. I was able to straighten them and put it back in the socket but I'm worried I could have damaged it. Any thoughts?
Jack
Jack
Jax2A
Yahoo, Success!
David, While I don't have it installed on an engine yet and can't get an RPM signal, I did a sucessful first test today. First I hooked up my MegaJolt to the desktop and input a test map. Was able to add/change/etc. Disconnected power and everything stayed the same. Seems to work, YEA for me I did it! Then I hooked up my Axim to test your program and my auxilliary 3.5mm audio/serial port. Started your program and hit "Fetch". Pulled up all the test values I had input. Also changed some values and burned them. Then disconnected everything and hooked back up to the desktop. The burned values were still there. How cool, it seems I've got this thing licked and your program seems to work fine. Can't wait to get this hooked up to a motor to test it all. Thanks for all your help.
Jack
Jack
Jax2A
Excellent
Excellent work, sounds great. It is all worth it by the way - I had my first EDIS powered drive yesterday and the transformation is incredible!
However, I do need to improve my pocket pc program to make it really useful; a real time read out of MAP and revs (perhaps highlighting the current advance figure in the MAP) will make on-the-road tuning much easier!
David
However, I do need to improve my pocket pc program to make it really useful; a real time read out of MAP and revs (perhaps highlighting the current advance figure in the MAP) will make on-the-road tuning much easier!
David