Howto Readout usb-ftdi-ttl-232-cable
#1
Posted 01 September 2012 - 09:10 AM
#2
Posted 01 September 2012 - 09:37 AM
I have a technical question and am looking for the very best solution.
We want to readout a rs232 signal from a electric "smart" home meter.
Can I connect a cable like this directly into the USB of the N+?, and if so how to approach this USB connection?
http://www.adafruit....ng-immediately/
Or must I use a breakoutboard like this one, is this the best solution.?
https://www.sparkfun.com/products/9716
I'm curious
I would not even consider connecting the output from the meter to the USB on the N+. I would put together a MAX232 circuit and connect the meter to the MAX232 and the MAX232 to one of the N+ serial ports.
The MAX232 circuit only needs the chip and a few capacitors (5 I think) and the circuit you will need it in the datasheet for the chip. I've put one of these together in the past and it takes a few minutes on breadboard. You might also have to take the logic levels into consideration as the N+ can tolerate 5V input but only allows 3.3V output.
Regards,
Mark
To be or not to be = 0xFF
Blogging about Netduino, .NET, STM8S and STM32 and generally waffling on about life
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#3
Posted 01 September 2012 - 06:36 PM
#4
Posted 01 September 2012 - 07:34 PM
Can I connect a cable like this directly into the USB of the N+?, and if so how to approach this USB connection?
Here is a USB to Rs232 adapter,
These two things are very different....
Unless I'misunderstood, the question is can I connect from RS-232 to the N+ using USB on the N+.
Regards,
Mark
To be or not to be = 0xFF
Blogging about Netduino, .NET, STM8S and STM32 and generally waffling on about life
Follow @nevynuk on Twitter
#5
Posted 02 September 2012 - 05:16 AM
#6
Posted 02 September 2012 - 03:47 PM
#7
Posted 02 September 2012 - 07:59 PM
#8
Posted 05 September 2012 - 02:23 PM
I would look to build a circuit like this:
ND_UART<-->MAX232<-->4N36<-->smart meter
Nak.
#9
Posted 06 September 2012 - 07:59 AM
Thank you Nak, Baxter...for your clear explanation.
I would look to build a circuit like this:
ND_UART<-->MAX232<-->4N36<-->smart meter
Nak.
Please can you offer me a link where to buy?.
This is not for myself but for my father (who can not read/write English) and my friend who does .....nothing. We will post a diagram here before we connect. I do not want to blow up the meter.
Ellen
#10
Posted 06 September 2012 - 09:49 AM
Thank you Nak, Baxter...for your clear explanation.
Please can you offer me a link where to buy?.
This is not for myself but for my father (who can not read/write English) and my friend who does .....nothing. We will post a diagram here before we connect. I do not want to blow up the meter.
Ellen
Hi Ellen
Maxim actually make a chip designed to drive opto isolaters, the MAX250 the datasheet is here (PDF)
RS stocks them here: http://uk.rs-online....=max250&x=0&y=0
However you may want to request a free sample from Maxim, they offer the 14pin DIP package for sample/evaluation here http://www.maximinte...vp/id/1310/t/or the model you want is the MAX250CPD+ you need to register for a free account but other than the occasional marketing email thats the only catch...
As for the opto isolaters them selves i have used 4N34,4N35 and 4N36's in the past, as you stated cost is a deciding factor RS stocks 4N35's available in single quantities here the rest are usually in bags of 10 or 20 here. There may be better component suppliers for main land europe, but RS and Farnell both offer Dutch versions of their websites if that helps...
http://nl.rs-online....rm=4N35&x=0&y=0
Nak.
#11
Posted 09 September 2012 - 09:15 AM
But the most simple Arduino can do the job without any additional hardware...
SoftwareSerial Library
The SoftwareSerial library has been developed to allow serial communication on other digital pins of the Arduino, using software to replicate the functionality (hence the name "SoftwareSerial"). It is possible to have multiple software serial ports with speeds up to 115200 bps. A parameter enables inverted signaling for devices which require that protocol.
SoftwareSerial myOwnSerial(10, 11, true); // RX, TX, inverted
http://arduino.cc/en.../SoftwareSerial
So about serial communication, am I a little disappointed in the netduino.
#12
Posted 09 September 2012 - 10:20 AM
#13
Posted 25 September 2012 - 02:17 PM
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