Re: Writing pins to the RS232
Jay,
Couple of points that may help you.
1) A serial port does not have data ports 0-n. A serial port takes a
byte (8 bits), then shifts them down a single pipe using a chip called a
UART (feel free to google for unfamiliar terms).
example
Bit pattern 1010 1010
would be shifted one bit at a time
1
0
1
0
1
0
1
0
a one is +5 volts on single send line of the UART and 0 is 0 volts.
RS232 uses a different mapping for 1's and 0's (but is still serial)
1 - ~-3V - -12 V
0 0-12 V
So you slap a chip on between the UART and the RS232 pin (usually a
MAX232) that translates the voltages for you.
On the other end of the wire
232 socket
MAC232
UART (usually built into the microcontroller)
Register in Microcontroller
I like playing at this level. I would recommend using AVR
microcontroller (easiest to program and there is an open source
gcc compiler).
for $20.00 US you can buy the butterfly eval board with:
- microcontroller
- max232 all wired up for rs232 connection from your computer
- lcd display
- temperature sensor
- light sensor
- the avr mega169 has many goodies
- analog - digital converter
- digital - analog converter
- LCD controller
This is a great bargin.
If you are starting out in microcontrollers. I would suggest that you
go to:
http://smileymicros.com/
They sell a nice package for $90.00
- butterfly eval board
- great, easy to follow book on how to develop on microcontrollers for
the beginer.
- project kit - includes everything you need to build all of the
projects (even includes the wire ;-)
There are python libs that support Ateml Avr connections:
It is easy to use your rs232 serial with a microcontroller at the other
end of the wire. Microcontrollers are cheap. If you fry why is
connected to your devices, you are only out the microcontroller.
Have fun,
Mike
[EMAIL PROTECTED] wrote:
I want to write to the pins of an RS232 without using the serial
protocol. The use would be every pin could act to complete a circuit
in customized hardware. I could use python to communicate serially to
a BASIC stamp or a Javelin stamp and then use the stamp to set however
many pins as 0's or 1's but should it be that hard to do with python.
I've looked through how python does serial with the serial module but
it just uses Java's javax.comm libraries. Is there anyway to do very
low level device writing to COM ports?
In summary I'm looking for something like:
ser = serial.Serial(0)
ser.pin0 = 1
ser.pin1 = 1
ser.pin2 = 1
or
ser.write('0xFF')
which would set 8 pins on the RS232 cable to 1's
--
The greatest performance improvement occurs on the transition of from
the non-working state to the working state.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
For those looking, I've already used IC's that convert RS232 to TTL, look up MAX233. It drops 12 to 5, essentially converting RS232 to TTL and vice versa. PyParallel is definitely the way I'll go, however, this project will be on hold for me for my priorities have been shifted. Thanks again for all of your help. -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
Richard Brodie [EMAIL PROTECTED] wrote: If you just need one or two signals, then it might be practical to use one of the control lines, and PySerial supports this (UPS monitoring software often works this way). I've done this many times (not with PySerial) for misc sensors. With PySerial you can read 4 pins (ie 4 inputs) getCD(self) Read terminal status line: Carrier Detect getCTS(self) Read terminal status line: Clear To Send getDSR(self) Read terminal status line: Data Set Ready getRI(self) Read terminal status line: Ring Indicator and set two outputs setDTR(self, on=1) Set terminal status line: Data Terminal Ready setRTS(self, on=1) Set terminal status line: Request To Send Other than those 6 that you have Rx, Tx and Ground which you can't use for logic, on a standard 9-way PC serial port. You need to set the serial port up not to do automatic handshaking first (eg setDsrDtr() setRtsCts()) RS232 levels are +/- 12V, though a lot of computers only generate +/- 5V. The threshold is +/- 3V IIRC. -- Nick Craig-Wood [EMAIL PROTECTED] -- http://www.craig-wood.com/nick -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
Roy Smith [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: While I realize this is more on a driver/hardware level it's interesting that it's so difficult to use a different protocol for an existing driver. For example, all serial does is a series of high and low voltages on specific pins. Why should it be so hard to use an existing driver and hold a pin on high? It's been a long time since I've looked at this low-level hardware, but the answer is almost certainly, No just 'so hard', but 'impossible'. If you just need one or two signals, then it might be practical to use one of the control lines, and PySerial supports this (UPS monitoring software often works this way). Setting 8 pins to 1 would be impossible, because there plain won't be that number of outputs wired, in addition to all the good stuff about UARTs Roy said. -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
Richard Brodie wrote: If you just need one or two signals, then it might be practical to use one of the control lines, and PySerial supports this (UPS monitoring software often works this way). Setting 8 pins to 1 would be impossible, because there plain won't be that number of outputs wired, in addition to all the good stuff about UARTs Roy said. All true, but then Jay might get into electrical compatibility issues, and may not realize that the output levels of RS-232 serial hardware are not simply 0 and 5V levels, but rather +9V (or so) and -9V (and with variations from 6V up to 13V seen in the wild), and without much in the way of drive capability. Using this to control custom hardware would probably be an exercise in frustration and kind of pointless in comparison to using parallel hardware, which at least has more typical logic voltage levels. -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
Peter Hansen [EMAIL PROTECTED] wrote in news:[EMAIL PROTECTED]: All true, but then Jay might get into electrical compatibility issues, and may not realize that the output levels of RS-232 serial hardware are not simply 0 and 5V levels, but rather +9V (or so) and -9V (and with variations from 6V up to 13V seen in the wild), and without much in the way of drive capability. Using this to control custom hardware would probably be an exercise in frustration and kind of pointless in comparison to using parallel hardware, which at least has more typical logic voltage levels. You can get ICs that convert RS232 to TTL voltage levels. -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
Hi,
Some of it should be doable on windows:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wcecoreos5/html/wce50lrfescapecommfunction.asp
Yet this might require a new wrapper module for I am not sure what the
current interface lets you do.
Not sure about Linux.
Regards;
Philippe
On Fri, 25 Nov 2005 13:25:44 -0800, [EMAIL PROTECTED] wrote:
I want to write to the pins of an RS232 without using the serial
protocol. The use would be every pin could act to complete a circuit
in customized hardware. I could use python to communicate serially to
a BASIC stamp or a Javelin stamp and then use the stamp to set however
many pins as 0's or 1's but should it be that hard to do with python.
I've looked through how python does serial with the serial module but
it just uses Java's javax.comm libraries. Is there anyway to do very
low level device writing to COM ports?
In summary I'm looking for something like:
ser = serial.Serial(0)
ser.pin0 = 1
ser.pin1 = 1
ser.pin2 = 1
or
ser.write('0xFF')
which would set 8 pins on the RS232 cable to 1's
--
http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
First of all I'd like to thank all of you for your input. It's nice to have a place to throw ideas around and get some feedback. I think the reason the serial source code I'm using is using javax.comm stuff which is possibly part of Jython is because I'm on Mac OS X. However this is just my guess as all of this is translucent to me and difficult for me to decipher. While I realize this is more on a driver/hardware level it's interesting that it's so difficult to use a different protocol for an existing driver. For example, all serial does is a series of high and low voltages on specific pins. Why should it be so hard to use an existing driver and hold a pin on high? I guess the answer is, because the driver is operating system specific, and because all of the drivers and code that use that driver use the hardware in a very specific way. If you ever wanted to use it for a different purpose you'd have to start all the way at the bottom again. While I can just use a serial protocol to tell a chip to do what I'm looking for it seems like an extra piece of hardware I don't need. Looking into pyparallel, it seems this is much closer to my needs. Now I just need to purchase a usb to parallel adapter and do some further experimenting. Looking up some diagrams of how the parallel ports work and some useful documentation I don't think I'll be running into any more problems. -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
[EMAIL PROTECTED] [EMAIL PROTECTED] wrote: While I realize this is more on a driver/hardware level it's interesting that it's so difficult to use a different protocol for an existing driver. For example, all serial does is a series of high and low voltages on specific pins. Why should it be so hard to use an existing driver and hold a pin on high? It's been a long time since I've looked at this low-level hardware, but the answer is almost certainly, No just 'so hard', but 'impossible'. A serial port is driven by a thing called a UART (Universal Asynchronous Receiver/Transmitter). Back when I was playing with these things, a UART was a discrete chip; these days I'm sure it's just a minor part of a more complex I/O processor, but I suspect the basic idea is the same. You load a character to be transmitted into a register on the UART and the hardware takes care of all the low-level gunk like clocking the bits out at the correct rate, adding start and stop bits, and computing parity. And the reverse for the receive side of the house (which is usually the more complicated part). There just isn't any way to tell the hardware to do anything other than it was designed to do. Could you design a piece of hardware which could function as both a serial port and what you want? Sure you could, but it would cost more, and PC design today is a matter of shaving 10 cents here and 30 cents there. It's like looking at a microwave oven and saying, Can't this thing be reprogrammed to be a communications relay? Well, sure, it's got some of the same parts, but the parts were put together in a way that makes food get hot, not in a way that makes data bits get transmitted to someplace. -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
ahhh I understand now -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
[EMAIL PROTECTED] wrote:
I want to write to the pins of an RS232 without using the serial
protocol. The use would be every pin could act to complete a circuit
in customized hardware. I could use python to communicate serially to
a BASIC stamp or a Javelin stamp and then use the stamp to set however
many pins as 0's or 1's but should it be that hard to do with python.
I've looked through how python does serial with the serial module but
it just uses Java's javax.comm libraries. Is there anyway to do very
low level device writing to COM ports?
In summary I'm looking for something like:
ser = serial.Serial(0)
ser.pin0 = 1
ser.pin1 = 1
ser.pin2 = 1
or
ser.write('0xFF')
which would set 8 pins on the RS232 cable to 1's
Accessing hardware at this level is almost always managed by some form
of device driver in any real operating system. Even Microsoft Windows
has device drivers for serial and parallel ports. This is not your
father's MS-DOS any more. It would be a security breach to allow user
applications direct access at the hardware level.
Also, if you ever hope to run on anything except an IBM-PC clone, then
the hardware will be different. Even systems that run x86 processors
like the NEC PC-98 have 8255 parallel interfaces, but they are located
on different ports in the machine.
--
http://mail.python.org/mailman/listinfo/python-list
Writing pins to the RS232
I want to write to the pins of an RS232 without using the serial
protocol. The use would be every pin could act to complete a circuit
in customized hardware. I could use python to communicate serially to
a BASIC stamp or a Javelin stamp and then use the stamp to set however
many pins as 0's or 1's but should it be that hard to do with python.
I've looked through how python does serial with the serial module but
it just uses Java's javax.comm libraries. Is there anyway to do very
low level device writing to COM ports?
In summary I'm looking for something like:
ser = serial.Serial(0)
ser.pin0 = 1
ser.pin1 = 1
ser.pin2 = 1
or
ser.write('0xFF')
which would set 8 pins on the RS232 cable to 1's
--
http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
In article [EMAIL PROTECTED], [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: I want to write to the pins of an RS232 without using the serial protocol. The use would be every pin could act to complete a circuit in customized hardware. I could use python to communicate serially to a BASIC stamp or a Javelin stamp and then use the stamp to set however many pins as 0's or 1's but should it be that hard to do with python. I've looked through how python does serial with the serial module but it just uses Java's javax.comm libraries. Is there anyway to do very low level device writing to COM ports? This really isn't a Python question -- it's a low-level hardware question. The short answer, however, is that it's almost certainly impossible to anything like what you want, for a number of reasons. The output pins on the connector are driven directly by some sort of serial hardware driver, and the hardware almost certainly doesn't expose an interface which lets you do what you're after. I think want you want to be doing is looking at using a parallel port (commonly called a printer port on PC's). But in any case, the answer to How do I make the parallel port do this? is a low-level hardware question, not a Python question. -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing pins to the RS232
[EMAIL PROTECTED] wrote: I want to write to the pins of an RS232 without using the serial protocol. The use would be every pin could act to complete a circuit in customized hardware. I could use python to communicate serially to a BASIC stamp or a Javelin stamp and then use the stamp to set however many pins as 0's or 1's but should it be that hard to do with python. I've looked through how python does serial with the serial module but it just uses Java's javax.comm libraries. Is there anyway to do very low level device writing to COM ports? As Roy indicates, you can't practically make a serial port on a PC do this. I just wanted to note that you've misunderstood the presence of the Java stuff in pyserial. If you're running under Jython then that stuff is used, but if you're on Windows the file win32serial.py (or something like that... going by memory) is what will be used, not the java one. Also, pyparallel should let you get closer to what you want, and in fact questions about using it are certainly on-topic here, though troubleshooting hardware issues are probably not. -Peter -- http://mail.python.org/mailman/listinfo/python-list
