Mmmh... Except that logical 1 in RS232 must be a *negative* voltage (between -5 and -15V), so I think the MAX chip is really neededOriginally Posted by guest
I think that the signal is inverted but ready to connect to rs232 of PC. The idle level output from uart is logical 1 ttl (4-5volt) but when you interface the rs232 the levels are inverted and idle is 0Volt (belove 3v).
So the start bit at uart output is logical 0 but on the rs232 connector will be +12V. I'am very interested too, i have a Scenic with tunerlist.
Yes indeed... I think it will be much easier when we've got more samples to work on, to compare successive values. That's what I'm working on right now...Originally Posted by Putput
Perhaps you can help me indeed. See post below.
Thanks for your proposal.
Well, levels are now OK.
Here are the adaptations I made to the spy circuit :
- lower the input voltage with resistor dividers. I chose 68K and 22K, giving me a factor of 22/(68+22) ~= 0.25. So input level of 3V gives 0.75V and 12V gives 3V, which is perfectly in the working range of the MAX circuit - see data sheet on http://pdfserv.maxim-ic.com/en/ds/MAX3222-MAX3241.pdf
- tie pin 1 of each serial port with already connected pins 4 and 6, following the recommandation of the first schema on http://www.airborn.com.au/rs232.html
- fixed the errors in the wiring of the second serial port
These changes are included in the schema below.
*** EDIT : Schema removed again. Signal needs to be inverted !
Working circuit available in post 197 ***
Now I have a "perfect" signal. The scope captures below are from pins 11 (T1IN) and 14 (T1OUT) of the MAX3232, respectively. So obviously, I'm in the correct range...
However, on the PC, I cannot get anything in Hyperterminal or MTTTY (sample MSDN application - see http://msdn.microsoft.com/library/de...sdn_serial.asp )
I see two possible reasons :
- Wrong wiring of serial port
- Loopback handshake is not supported by these apps.
Can someone with experience on serial communications (Putput ?) comment on this ?
Thanks - the mission continues...
Vicne, may be this could help to : http://rt3wiki.free.fr/pmwiki.php?n=Us.Document
It deals with Peugeot's RD3 Headunits on a VAN bus, but the idea is the same : fool the HU into thinking there's a CDC.
Now Galileo is real. Muhahahahaha :p
Hard to tell, has probably something to do with port settings and/or handshaking. When nothing gets trough the port seems to blocked or waiting for something, try this http://www.serial-port-monitor.com/d...t-monitor.html program instead of Hyperterminal to monitor, its free.
Thanks. Mox already pointed me to it, but as I read the description, I thought it was only an "interceptor" between a working Windows host application and a remote device. In my case, as I have no windows app (yet) to communicate with the head unit, I thought it was useless.Originally Posted by Putput
Although, I just downloaded and started it and this seems that as soon as hyperterminal opens the port (no matter if settings are correct or not), the monitoring begins even though hyperterminal doesn't display a single character. I could only test it with an old serial mouse for now, but I'll give it a try at home tonight.
The only thing that I'm still unsure of is the wiring of the DB9 plug...
(and sorry Mox not to have followed your advice at first)
As far as I can tell the connections are ok, 2 is receive, 4 is DTR connected to 6 DSR, 7 is RTS connected to 8 CTS. So hardware handshaking should be ok. You could try to disconnect DCD but I don't think that it would make any difference. Perhaps you can also try to connect pin 3 to the MAX232, maybe the UART detects this?? You can use Port Monitor to send/receive data to a serial port by means of the Console View window after opening Hyperterminal via Tools, Terminal and select the connected serial port.
Hey Vicne, thanks for the heads-up (I tried to reply but wasn't allowed?!?), I was already (silently) following this threadOriginally Posted by Vicne
Nothwistanding the fact that hyperterminal is a pile of s*** (cannot comment on MTTY) that I never managed to use without handshaking (and even with handshaking works badly), it may simply be that you didn't find the right combination of speed/stop bits/parity (thouh at least you should see some garbage once the receiver detects a start bit, but I doubt hypers*** will show you the garbage).
I don't know of good terminal emulation programs for windows (I usually cook my quick and dirty tests in delphi or use minicom under linux) but a quick search (and following the above link) I found these two programs:
The latter uses some ms control for the serial port, so, while visually impressive, I don't know how good it is, the former I didn't check.