OT quicky

[jmumby]

Well, end result will use a picaxe.

I need to use CTS/RTS from a PC. I already have a MAX232 setup to use TX and RX would it just be a case of setting up another MAX232 and lash up the CTS and RTS lines?

Cheers,

 

[Andrew Cowan]

Yes. CTS and RTS are the usual 12V/-12V, so a MAX232 will do the job.

A

 

[manuka]

I've just been doing RS232-TTL conversions for HopeRF TTL circuitry , so am a very minor 5 minute expert on the topic. Did you realise that the MAX232 is a dual driver/translator IC? Hence consider just using the ICs spare channel connections? There are many cheaper discrete component conversion techniques for non critical work of course- ref a bipolar approach below, although N-FET are superior. Stan

 

[jmumby]

Hang on, Would the MAX232 invert the signals?

 

[Dippy]

All the ones I have used will, yes.
Maybe there are other options? Have a search.

 

[jmumby]

I usually Pre-google before asking here. Plenty of info on TX and RX, CTS and RTS are out in the cold. I need it for xmodem oohhhhhh errrrrrrr BBS talk.

 

[hippy]

I need to use CTS/RTS from a PC. I already have a MAX232 setup to use TX and RX would it just be a case of setting up another MAX232 and lash up the CTS and RTS lines?

There's a serious lack of context there and no indicator of what it's in relationship with.

Another MAX232 will convert 0V/5V to +/-12V serial lines and vice-versa, CTS and RTS, but whether that will achieve what you need depends on what it is you are trying to do and how, how these signals need to be used.

Depending upon exactly what your "MAX232" is, there may be additional drivers within the chip ready to be used or it may be necessary to get an additional chip.

 

[moxhamj]

Yes the max 232 will invert the signal but that is what you want. Resting volts on the RS232 is -9V and resting volts for a TTL signal is +5V. That is the standard used by uarts etc and the exception is the picaxe programming system where the signal is not inverted.

The max 232 has 4 gates so one chip can do rts and cts and the two data lines.

I agree with hippy about the lack of context. xmodem doesn't need rts and cts. I just have finished coding with xmodem in both vb.net and z80 assembly. xmodem uses
EOT = chr(4) = CTRL-D = End of Transmission
ACK = chr(6) = CTRL-F = Positive Acknowledgement
NAK = chr(21) = CTRL-U = Negative Acknowledgement
CAN = Chr(24) = CTRL - X = Cancel

to control the transfer of 128 byte blocks, so it will work fine with a 3 wire serial connection. Unless you are talking to a modem or something.

xmodem is neat. Tonight the wireless mesh went live with two boards and a PC all working wirelessly. Sent a file from the pc to one board. Then sent instructions to do xmodem 'send' on that board and sent instructions to do xmodem 'receive' on the other. Now files can hop from one board to the next via commands that themselves have hopped via many boards to get there. The concept has been proven to work. I don't reckon xmodem will fit in an 18x but it could well fit in the chips above the 18X...

 

[jmumby]

Yes, sorry a bit vauge. I'm trying to hook up a dos-on-chip but I need to update the firmware so I can use uart without cts/rts. But to update the firmware I must use xmodem and cts rts from a pc.

Slightly OT but promise to post examples so you can add fat16/32 sd card support to your project for US$10.

 

[jmumby]

Yes the max 232 will invert the signal but that is what you want. Resting volts on the RS232 is -9V and resting volts for a TTL signal is +5V. That is the standard used by uarts etc and the exception is the picaxe programming system where the signal is not inverted.

The max 232 has 4 gates so one chip can do rts and cts and the two data lines.

This is correct and works. What also works is finding out that your FT232R breakout board also has CTS RTS so going to that effort of lashing up the other MAX232 ports was actually a complete waste of time. A further waste of time is finding out that the firmware update you wanted to do has pretty much made the dosonchip useless because there is no documentation for the new firmware other than a c API which means nothing to me.

Thanks for the help