BasicMicro - Forums

I would like to use a standard rs232 programming port on a project and use a standard db9 connector. I have seen some posts, and I have tried setting up a port using a max232, but haven't been able to get it to work. Has anyone posted a schematic of the max232 hookup that I haven't found? Any help would be appreciated. Thanks.

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Harley

Try the app notes for the chip.

Look at SchmartBoards, they have an RS-232 module. Schematic supplied. I've bought several for work, and I've found it useful for a recent 'bot project!

http://www.schmartboard.com/index.asp?page=products_populated&id=84

http://www.schmartboard.com/schmartboard_pd_710-0001-01.pdf

Alan KM6VV

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Thanks Alan, I'll give them a try.

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Harley

I have tried connection the max232 as shown at SchmartBoard with no success. It seems confusing as the schematic shows the device TD pin connected to pin 3 on the DB9, thru the max232,which is the transmitted data pin. In the Atom nano18 data sheet, the SOUT(TD) connection should be connected to the RX(receive) pin on the DB9(pin2). It also shows the TD device pin hooked to the R2OUT pin on the max232 which seems odd. Shouldn't the transmitted data be sent to a receive pin on the 232 and then sent out on the R2OUT pin? I have tried different combinations also with no success. It simply can't find the nano and the nano works fine with the usb2serial hookup. For something so simple, I am extremely confused!

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Harley

Sorry, you've lost me. Can you post a schematic?

Device_RD wants to be connected to the TX line of the PIC (nano).

Device_TD want to be connected to the RX line of the PIC.

Don't forget the ground!

CTS and RTS are available, but don't need to be connected for the Nano to talk to a PC.

Programming would require the RTS line to be connected, (just mentioned on another thread) pin 6? Don't quote me!

I need to dig up a Nano manual before I can answer more. Perhaps the forum owners can comment more until I get a chance.

I KNOW the RS-232 board I mentioned works! I would mention that I use it for comms, not for programming (not that it shouldn't work), I'm connected to PIC processors via the ICP programming interface...

Alan KM6VV

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I went to the link you provided for the SchmartBOARD and downloaded the pdf schematic file. I now have the port working. I had a couple of problems when setting up the breadboard. First and probably the dumbest problem was that I bent pin 9 over when inserting the max232. The other problems were interpreting the schematic, and on the SchmartBOARD R2OUT(9) is connected to the SIN signal and T2IN(10) is connected to the SOUT signal. CTS on the SchmatBOARD is not used and RES is connected to R1OUT(12) pin. The rest of schematic is correct. I will try to post the schematic now that it is working. The port is now working for programming, but I haven't tried it for comm yet, so I don't know if its perfect yet. It should be noted that the pullup resistors and the diode shown in the Nano18 datasheet are also required.
Thanks for your help!
This was the link for the SchmartBOARD and has the complete schematic.
http://www.schmartboard.com/schmartboar ... 001-01.pdf

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Harley

Glad it's working! Yes, please post your schematic.

They make nice boards.

Alan KM6VV

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I have attached a pdf file that shows the setup for using a Max232 chip to set up a serial port on the Nanos. Hope it helps and makes it easy. I can program the nanos and communicate with the nanos using this circuit.

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Harley

that should do it.

Thanks for posting your circuit.

You might even want to add the Nano resistors and diode to your drawing.

Alan KM6VV

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