usb serial programming

usb serial programming

[Amadeus W.M.]

Not sure if this is the right venue for this question, please direct me to
the right place if it's not.

I have a C program that opens the serial port /dev/ttyS0 and sends commands 
(as strings) back and forth to a pan-tilt-zoom camera. That works very well,
but I want to use the camera with a Raspberry Pi, which of course does not 
have a serial port (RS232). One option is to use a RS232 to usb adapter and 
rewrite the C code for the usb port. So how do I go about that? Is
usb serial port programming possible and documented anywhere? 

Thanks!

usb serial programming

[Greg KH]

On Mon, Jul 21, 2014 at 03:19:00AM +0000, Amadeus W.M. wrote:
> Not sure if this is the right venue for this question, please direct me to
> the right place if it's not.
> 
> I have a C program that opens the serial port /dev/ttyS0 and sends commands 
> (as strings) back and forth to a pan-tilt-zoom camera. That works very well,
> but I want to use the camera with a Raspberry Pi, which of course does not 
> have a serial port (RS232). One option is to use a RS232 to usb adapter and 
> rewrite the C code for the usb port. So how do I go about that? Is
> usb serial port programming possible and documented anywhere? 

Nothing to "rewrite", just point your code at /dev/ttyUSB0 instead, and
away you go...

usb serial programming

[Bruce Rowen]

Assuming your camera is RS232, you can use a simple RS232 daughter card on the Raspberry (about $7 from MCM electronics and others).
I have done this exact thing for communications with an old RS232 device.

Alternative is of course a USB to RS232 adapter and as Greg writes, you just change the target device file (the $7 adapter also creates a /dev/ttyxxx device.

-Bruce
On Jul 21, 2014, at 12:18 PM, Greg KH <greg@kroah.com> wrote:

> On Mon, Jul 21, 2014 at 03:19:00AM +0000, Amadeus W.M. wrote:
>> Not sure if this is the right venue for this question, please direct me to
>> the right place if it's not.
>> 
>> I have a C program that opens the serial port /dev/ttyS0 and sends commands 
>> (as strings) back and forth to a pan-tilt-zoom camera. That works very well,
>> but I want to use the camera with a Raspberry Pi, which of course does not 
>> have a serial port (RS232). One option is to use a RS232 to usb adapter and 
>> rewrite the C code for the usb port. So how do I go about that? Is
>> usb serial port programming possible and documented anywhere? 
> 
> Nothing to "rewrite", just point your code at /dev/ttyUSB0 instead, and
> away you go...
> 
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

usb serial programming

[Amadeus W.M.]

On Mon, 21 Jul 2014 11:18:28 -0700, Greg KH wrote:

> On Mon, Jul 21, 2014 at 03:19:00AM +0000, Amadeus W.M. wrote:
>> Not sure if this is the right venue for this question, please direct me to
>> the right place if it's not.
>> 
>> I have a C program that opens the serial port /dev/ttyS0 and sends commands 
>> (as strings) back and forth to a pan-tilt-zoom camera. That works very well,
>> but I want to use the camera with a Raspberry Pi, which of course does not 
>> have a serial port (RS232). One option is to use a RS232 to usb adapter and 
>> rewrite the C code for the usb port. So how do I go about that? Is
>> usb serial port programming possible and documented anywhere? 
> 
> Nothing to "rewrite", just point your code at /dev/ttyUSB0 instead, and
> away you go...

Thanks for the prompt answer!

That's what I was hoping for, and I would have tried that, but I don't
have any /dev/ttyUSBX. I am connecting the camera to a usb to RS232 
cable:

http://www.amazon.com/gp/product/B000BI95W0/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

Does this mean my adapter is not supported by linux? Also, nothing 
happens in /var/log/messages when I plug the cable into the usb port. 
This is my lsusb:

1) root:~> lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 003: ID 0c45:1050 Microdia CF Card Reader
Bus 005 Device 002: ID 046d:c016 Logitech, Inc. Optical Wheel Mouse
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 008: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 005: ID 04fc:0561 Sunplus Technology Co., Ltd Flexcam 100
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

No trace of the adapter.


Should /dev/ttyUSB0 pop up when I plug the adapter into the usb port,
even before I connect anything to the serial port of the cable? 

If the adapter is not supported, can I write a driver for it? I'll be happy to,
with a little guidance to get me started. Any pointers?

Thanks!

usb serial programming

[Amadeus W.M.]

On Mon, 21 Jul 2014 12:27:44 -0600, Bruce Rowen wrote:

> Assuming your camera is RS232, you can use a simple RS232 daughter card on the Raspberry (about $7 from MCM electronics and others).
> I have done this exact thing for communications with an old RS232 device.
> 
> Alternative is of course a USB to RS232 adapter and as Greg writes, you just change the target device file (the $7 adapter also creates a /dev/ttyxxx device.
> 
> -Bruce
> On Jul 21, 2014, at 12:18 PM, Greg KH <greg@kroah.com> wrote:
> 

Thank you, that's useful. This, you mean?

http://www.mcmelectronics.com/product/83-15630

This one is for Arduino. I couldn't find one for Pi on the MSM site, but 
knowing what to search for lead me to a plethora of expansion cards for 
the RPi:

http://elinux.org/RPi_Expansion_Boards#RS232_to_TTL_converter

Thank you for the pointer.

usb serial programming

[Greg KH]

On Mon, Jul 21, 2014 at 06:55:43PM +0000, Amadeus W.M. wrote:
> On Mon, 21 Jul 2014 11:18:28 -0700, Greg KH wrote:
> 
> > On Mon, Jul 21, 2014 at 03:19:00AM +0000, Amadeus W.M. wrote:
> >> Not sure if this is the right venue for this question, please direct me to
> >> the right place if it's not.
> >> 
> >> I have a C program that opens the serial port /dev/ttyS0 and sends commands 
> >> (as strings) back and forth to a pan-tilt-zoom camera. That works very well,
> >> but I want to use the camera with a Raspberry Pi, which of course does not 
> >> have a serial port (RS232). One option is to use a RS232 to usb adapter and 
> >> rewrite the C code for the usb port. So how do I go about that? Is
> >> usb serial port programming possible and documented anywhere? 
> > 
> > Nothing to "rewrite", just point your code at /dev/ttyUSB0 instead, and
> > away you go...
> 
> Thanks for the prompt answer!
> 
> That's what I was hoping for, and I would have tried that, but I don't
> have any /dev/ttyUSBX. I am connecting the camera to a usb to RS232 
> cable:
> 
> http://www.amazon.com/gp/product/B000BI95W0/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
> 
> Does this mean my adapter is not supported by linux? Also, nothing 
> happens in /var/log/messages when I plug the cable into the usb port. 
> This is my lsusb:
> 
> 1) root:~> lsusb
> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> Bus 005 Device 003: ID 0c45:1050 Microdia CF Card Reader
> Bus 005 Device 002: ID 046d:c016 Logitech, Inc. Optical Wheel Mouse
> Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 004 Device 008: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS
> Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 003 Device 005: ID 04fc:0561 Sunplus Technology Co., Ltd Flexcam 100
> Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> 
> No trace of the adapter.

What is the:
	Bus 004 Device 008: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS

device?

> Should /dev/ttyUSB0 pop up when I plug the adapter into the usb port,
> even before I connect anything to the serial port of the cable? 

Yes.

What happens in the kernel log when you plug the device into the system?

Try doing:
	dmesg -c
	# plug in the adapter now
	dmesg
to just see the log messages for that, and not the whole kernel boot
log.

> If the adapter is not supported, can I write a driver for it? I'll be happy to,
> with a little guidance to get me started. Any pointers?

Odds are the device id just needs to be added to an existing driver as
I do not know of any "new" usb-serial converter chips that Linux does
not already support.

thanks,

greg k-h

usb serial programming

[Amadeus W.M.]

> 
> What is the:
> 	Bus 004 Device 008: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS
> 
> device?

That's my backup power supply. 


> 
>> Should /dev/ttyUSB0 pop up when I plug the adapter into the usb port,
>> even before I connect anything to the serial port of the cable? 
> 
> Yes.
> 
> What happens in the kernel log when you plug the device into the system?
> 
> Try doing:
> 	dmesg -c
> 	# plug in the adapter now
> 	dmesg
> to just see the log messages for that, and not the whole kernel boot
> log.
> 
2) root:~> dmesg -c   #plug-in adapter
3) root:~> dmesg 

Absolutely nothing. I also did

tail -f /var/log/messages

then plugged in the adapter, and again, everything seems dead. The USB port
is ok, because other devices (e.g. the Fushicai video grabber) do work.


>> If the adapter is not supported, can I write a driver for it? I'll be happy to,
>> with a little guidance to get me started. Any pointers?
> 
> Odds are the device id just needs to be added to an existing driver as
> I do not know of any "new" usb-serial converter chips that Linux does
> not already support.
> 

Oh, one more thing. Reading about these converters, I saw many use an 
ftdi chip, so I did modprobed ftdi_elan and ftdi_sio:

7) root:~> lsmod | grep ftdi
ftdi_elan              36689  0 
ftdi_sio               48770  0 

In fact, the dmesg above was with the ftdi modules loaded.

usb serial programming

[Bruce Rowen]

On Jul 21, 2014, at 1:05 PM, "Amadeus W.M." <amadeus84@verizon.net> wrote:

> On Mon, 21 Jul 2014 12:27:44 -0600, Bruce Rowen wrote:
> 
>> Assuming your camera is RS232, you can use a simple RS232 daughter card on the Raspberry (about $7 from MCM electronics and others).
>> I have done this exact thing for communications with an old RS232 device.
>> 
>> Alternative is of course a USB to RS232 adapter and as Greg writes, you just change the target device file (the $7 adapter also creates a /dev/ttyxxx device.
>> 
>> -Bruce
>> On Jul 21, 2014, at 12:18 PM, Greg KH <greg@kroah.com> wrote:
>> 
> 
> Thank you, that's useful. This, you mean?
> 
> http://www.mcmelectronics.com/product/83-15630

It looks like they may no longer carry it, sorry. There are others out there, try googling 'raspberry serial port GPIO adapter'
> 
> This one is for Arduino. I couldn't find one for Pi on the MSM site, but 
> knowing what to search for lead me to a plethora of expansion cards for 
> the RPi:
> 
> http://elinux.org/RPi_Expansion_Boards#RS232_to_TTL_converter


The USB-serial adapter may be the more expedient solution at this point, 
Good luck!

> 
> Thank you for the pointer.
> 
> 
> 
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

usb serial programming

[Greg KH]

On Mon, Jul 21, 2014 at 07:25:24PM +0000, Amadeus W.M. wrote:
> > 
> > What is the:
> > 	Bus 004 Device 008: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS
> > 
> > device?
> 
> That's my backup power supply. 
> 
> 
> > 
> >> Should /dev/ttyUSB0 pop up when I plug the adapter into the usb port,
> >> even before I connect anything to the serial port of the cable? 
> > 
> > Yes.
> > 
> > What happens in the kernel log when you plug the device into the system?
> > 
> > Try doing:
> > 	dmesg -c
> > 	# plug in the adapter now
> > 	dmesg
> > to just see the log messages for that, and not the whole kernel boot
> > log.
> > 
> 2) root:~> dmesg -c   #plug-in adapter
> 3) root:~> dmesg 
> 
> Absolutely nothing. I also did
> 
> tail -f /var/log/messages

Then USB isn't working :(

Or the device isn't, can you plug it into some other computer to test it
out?

> then plugged in the adapter, and again, everything seems dead. The USB port
> is ok, because other devices (e.g. the Fushicai video grabber) do work.

Sounds like a broken device.

> >> If the adapter is not supported, can I write a driver for it? I'll be happy to,
> >> with a little guidance to get me started. Any pointers?
> > 
> > Odds are the device id just needs to be added to an existing driver as
> > I do not know of any "new" usb-serial converter chips that Linux does
> > not already support.
> > 
> 
> Oh, one more thing. Reading about these converters, I saw many use an 
> ftdi chip, so I did modprobed ftdi_elan and ftdi_sio:
> 
> 7) root:~> lsmod | grep ftdi
> ftdi_elan              36689  0 
> ftdi_sio               48770  0 
> 
> In fact, the dmesg above was with the ftdi modules loaded.

You should get some kernel log messages when a new USB device is plugged
in, no matter what type it is.  The fact that you are not is a problem.

greg k-h

usb serial programming

[Sudip Mukherjee]

On Mon, Jul 21, 2014 at 8:49 AM, Amadeus W.M. <amadeus84@verizon.net> wrote:
> Not sure if this is the right venue for this question, please direct me to
> the right place if it's not.
>
> I have a C program that opens the serial port /dev/ttyS0 and sends commands
> (as strings) back and forth to a pan-tilt-zoom camera. That works very well,
> but I want to use the camera with a Raspberry Pi, which of course does not
> have a serial port (RS232). One option is to use a RS232 to usb adapter and
> rewrite the C code for the usb port. So how do I go about that? Is
> usb serial port programming possible and documented anywhere?

Raspberry PI is not having a dedicated serial port but GPIO14 and
GPIO15 are the Rx and Tx pins , so you can just connect a max3232 to
have a serial port .

usb serial programming

[Amadeus W.M.]

>> In fact, the dmesg above was with the ftdi modules loaded.
> 
> You should get some kernel log messages when a new USB device is plugged
> in, no matter what type it is.  The fact that you are not is a problem.
> 
> greg k-h

Do you suppose this would work? 

http://www.amazon.com/gp/product/B006PIU2KO/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A3CTCSJRE9G6AY

usb serial programming

[Amadeus W.M.]

> Raspberry PI is not having a dedicated serial port but GPIO14 and
> GPIO15 are the Rx and Tx pins , so you can just connect a max3232 to
> have a serial port .

I believe that requires some capacitors and possibly some electronics, 
so I ordered one ready-made from China for $3 including shipping. 
It's on its way. Slowly.