Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

[PIC] 2 MAX232, HCF4066 & PIC microcontrollers

Status
Not open for further replies.

mmbabar41

Newbie level 2
Joined
Aug 16, 2015
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
23
Hi friends, I am using 2 MAX232, HCF4066 & PIC microcontrollers. I want to make communication of dial guage with PIC.
I have made connections for dial guage as given in image:
I tested dial guage by connecting to the PC through serial cable then dial guage is responds. Now I am able to transmit signal by enabling control pin of 4066 but not getting any response from dial guage. I am attaching the circuit diagram here. Please help me......
 

KlausST

Super Moderator
Staff member
Joined
Apr 17, 2014
Messages
21,980
Helped
4,591
Reputation
9,196
Reaction score
4,808
Trophy points
1,393
Activity points
145,108
Hi,

Please use the "insert image" button. insertImage.PNG

***
Mind to pullup unused TxD (idle high)

Klaus
 

Aussie Susan

Advanced Member level 4
Joined
Jan 5, 2015
Messages
1,413
Helped
393
Reputation
786
Reaction score
413
Trophy points
1,363
Activity points
16,545
I'm struggling to understand which signal you are having problems with. You have listed a number of different lines in the image but I can't work out which one has the "...response from dial guage[sic]...". Perhaps if you use the names as they are on the diagram it would help.
However I would suggest that you use a scope to trace the signal to see where it stops. Then you can again tell us what works and what doesn't using the labels from your diagram.
Susan
 

KlausST

Super Moderator
Staff member
Joined
Apr 17, 2014
Messages
21,980
Helped
4,591
Reputation
9,196
Reaction score
4,808
Trophy points
1,393
Activity points
145,108
Hi,

Susan is right, your description is confusing.

Mind to pullup unused TxD (idle high)
Ican't find the pullups.

Klaus
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
50,020
Helped
14,496
Reputation
29,262
Reaction score
13,426
Trophy points
1,393
Location
Bochum, Germany
Activity points
287,099
As far as I see, muxing the PIC UART between "Digital Dial" and "PC" RS-232 interfaces should work. I agree that the schematic could be better readable.

But the DB-9 pins assignment isn't standard RS-232, e.g. you have TxD at pin 4. As long we don't know the "dial gauge" interface operation, we can't guess what's the problem.

MAX232 has already internal weak pull-ups at /TXIN as far as I know,
 

spudboy488

Full Member level 5
Joined
Oct 10, 2012
Messages
272
Helped
69
Reputation
140
Reaction score
76
Trophy points
1,308
Activity points
3,058
Pin 4 is DTR and it might be used as a control/trigger to the "dial". It also looks like the communication is inbound (from the dial to the PIC) only. The pull-up to keep TX idle high (which it should be) is on U10, Pin 10.
 

KlausST

Super Moderator
Staff member
Joined
Apr 17, 2014
Messages
21,980
Helped
4,591
Reputation
9,196
Reaction score
4,808
Trophy points
1,393
Activity points
145,108
Hi,

With my expression "unused TxD" I meant "deselected TxD" = switched OFF

I read the datasheet. The pullup is about 400k. For unconnected pins this might be ok. But it is too weak for a signal that is wired to a CMOS switch.

Klaus
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top