Pages: [1]   Go Down
Author Topic: Serial in (RX) intermittent on Arduino clone  (Read 4328 times)
0 Members and 1 Guest are viewing this topic.
0
Offline Offline
Jr. Member
**
Karma: 0
Posts: 97
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hello

I've built an Arduino clone and all seems well apart from serial in on the RX pin appears intermittent (activity registered but garbled data) or non-functioning at all in some contexts (using a MIDI library). The odd thing is if I wire up my Duemilanove with same hardware and running same sketch all is well.

Is there something about the RX pin that my clone is missing? Pics attached.

Thanks
Jim



Logged

0
Offline Offline
Jr. Member
**
Karma: 0
Posts: 97
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I wired up a new Arduino on breadboard to double check it wasn't a short or continuity error with my DIY board ... same problem!

I've looked at various schematics and board layouts (clones and official boards) and the RX pin goes direct to a wire pad, nothing fancy at all, just like my board.

At a loss ... anybody?
Logged

0
Offline Offline
Jr. Member
**
Karma: 0
Posts: 97
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Needed 1k resistor between +5VDC and pin 0. See post here

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1294803960/0
Logged

nr Bundaberg, Australia
Offline Offline
Tesla Member
***
Karma: 126
Posts: 8499
Scattered showers my arse -- Noah, 2348BC.
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

You wouldn't normally need a pullup resistor on the RX pin, what's connected to it at the other end?

______
Rob

Logged

Rob Gray aka the GRAYnomad www.robgray.com

0
Offline Offline
Jr. Member
**
Karma: 0
Posts: 97
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

The output pin of a 4N25 opto-isolator that's part of a MIDI interface
Logged

nr Bundaberg, Australia
Offline Offline
Tesla Member
***
Karma: 126
Posts: 8499
Scattered showers my arse -- Noah, 2348BC.
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
The output pin of a 4N25 opto-isolator
That's why you need the resistor then as the opto OP is open collector, it either pulls low or is floating, so you need something to pull the line up.

It worked with a normal Arduino because there is a 1k resistor to the OP of the FTDI chip which will idle high, therefore you effectively have a pulll up resistor.

______
Rob

« Last Edit: January 12, 2011, 10:05:23 am by graynomad » Logged

Rob Gray aka the GRAYnomad www.robgray.com

0
Offline Offline
Jr. Member
**
Karma: 0
Posts: 97
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Thank you so much! That's great
Logged

Pages: [1]   Go Up
Jump to: