Frequently asked questions/IO
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Customers using Gumstix OpenEmbedded should go to gumstix.net and the related user wiki
Note: all gumstix verdex motherboards available at gumstix.com are pre-flashed with OpenEmbedded.
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If your question is not in this FAQ, please feel free to ask it on the Mailing list
What are the best practice procedures for getting a single signal into the gumstix as an interrupt or kernel signal?
The principle is to set a GPIO, serial, processor interrupt, or something similar as hot through one of the Hiroses or perhaps the breakout or robostix, and have something in kernel-space or user-land handle that and be able to take action.
The best way to do that would be to write a driver with an interrupt handler in it triggered off the GPIO transition.
In the userspace app, have a blocking ioctl call which unblocks when the interrupt fires.
What external interfaces does gumstix support?
The gumstix motherboards and their related expansion boards have a very broad range of supported interfaces,
Both gumstix motherboards provide a 60-pin hirose connector that gives access to 42 GPIO lines (3.3V logic), I2C, USB, and of course, power & ground. Most of the GPIO lines can be used in a form of alternate function. There are 3 UART ports, a NSSP, 2-PWM lines, AC97 (audio) controller, and LCD controller. There is also an MMC card slot and an optional bluetooth module. Testpoints on the motherboard provide access to JTAG.
for further details on the expansion capabilities of the gumstix products, Go to gumstix expansion boards.
How does a gumstix computer connect to a network?
Right now, you can buy a waysmall with bluetooth and be able to use usbnet-to-bluetooth to get started. When you get etherstix later, you'll just be talking on the eth0 network interface instead of the usb0 interface, but no code changes should be needed.
gumstix Linux includes a complete TCP/IP stack, and a fully functional PPPd, which will allow you to establish a network connection over any of the serial ports.
What speeds are the I2C bus capable of running at? Just 100kHz, or can it do 400kHz as well?
According to Intel's specs, the pxa255 can run the I2C bus at 100kHz or 400 kHz.
Is the USB interface on your board a USB HOST or a DEVICE interface?
Basix and Connex are device-only (kernel is compiled for a USB Ethernet Gadget). Verdex boards use USB-on-the-go, and can be configured as host or device (only host is working at the moment). See the USB article.
Which of the two din connectors on the waysmall computer is the console com port?
With the waysmall computer ports facing you, (as seen on the home page) the console com port is the port on the inside. Farthest from the right.
Which LCD screens/panels work with the gumstix?
The Gumstix's LCD controller can handle a wide variety of screens — monochrome, color, TFT - up to about 800x600, as long as it has a digital interface.
It seems that a good place to get LCD screens in single quantities is earthlcd.com — try
Earth LCD Store and click on "LCD panels"
Under the OEM section, there a several interesting choices. gumstix engineers have not tested these specific screens.
- Hitachi SX19V001ZZA - 7.5" Color STN 640 x 480 4096 CCFL - Price: $89.00
- Panasonic EDMGRB8KJF - 7.8" Color STN Touchscreen LCD - Price: $99.00
- Samsung UG24U01WGHT3A - 240x320 Transflective positive Graphic (monchrome) - EL Backlit FSTN - 3" PDA Touchscreen LCD (Includes Integrated Touch Screen) - Price: $39.00
- Sony 240 x 160 2.7" Color Reflective TFT Graphical Display with LED Frontlight (note: this has higher resolution than the au optronics display I mentioned earlier — this is really 240x160x3 colors, while the au one is more like 93x220 because it counts each color as a separate pixel) - Price: 1-19 $59, 20+ $49
- Optrex T-51963GD035J - 240x320 Colot TFT, LED Backlight. /etc/modules line: pxafb options=mode:240x320-16,active,hsynclen:100,vsynclen:1,left:20,right:0,upper:75,lower:2,pixclock:183000,hsync:1,vsync:1,outputen:1,pixclockpol:0
Are examples available on how to read/write the GPIO's ( not by /proc/gpio ... ) from a library?
Access the GPIOs should not be needed directly. The LCD driver in the linux kernel will do this. Compile in the LCD driver, and specify the LCD screen timing parameters that the driver needs to know about, which can be done on the kernel command line, or by hardcoding the parameters into the module.
Where can I get pinout information?
Click on this link:
Can the gumstix work with an LCD screen?
The LCD driver was working since back in Linux 2.6.10, using either the 8 bits per pixel mode (bbp) mode or the 16 bbp.
Some comments from one customer:
- I've just finished interfacing an EL panel from Planar which used the same interface format as an STN panel. My panel happened to have an extended tolerance for interfacing to 3.3V circuitry, so I didn't need anything else in between the panel and the gumstix. Check the specs on your panel's input voltage range. If your Vih min spec is above 2V, your're fine. If the Vih min spec is much above 2V, you might need a simple TTL level shifter to convert to the 3.8V or so that 5V TTL logic requires.
What is the link or schematic for the pin layout of hirose connector and the jtag pins on the waysmall board?
Gumstix motherboard I/O to go to the page with the pinout information.
If you look at your gumstix (hold it so the connector faces you and is at the top), on the lower right side of the connector, you'll see a big fat trace on the circuit board that connects to 3 pins on the connector. These are the V_BATT lines, which correspond to pins 28, 29, and 30.
Also, on the I/O page is an item which says Location on the gumstix-f board, with a link to a PDF. The PDF shows where pin 1 is located.
Which expansion boards allow connection an LCD panel?
You can use either breakout-gs, the Audiostix2 or the GPSstix expansion boards. Go to the Expansions#60-pin expansion boards page for more information.
Should a serial interface like Matrix Orbital LCD screens be used with the gumstix?
No, it's too expensive and not needed. The gumstix has an LCD interface built in, so using that you can add a much larger/better LCD screen at a much cheaper price then anything from Matrix Orbital. You pay heavily for their serial interface.
Where is the circuit diagram to build a serial cable?
Click Gumstix motherboard I/O#Serial cable connections for the serial cable connections, both null modem and straight through.
Worst case, flip two pins if the connection is backwards.
Which display(s) is recommended for the gumstix?
Holly Gates of eInk spent some time getting the sony 6.92cm color TFT set up on a gumstix. Check out this Display page.
Can PCB board with a Hirose connector be designed that will connect into the etherstix pack stack?
In order to create
- a high-speed parallel bus connection to a gumstix board (to an FPGA which can be programmed to match the bus specs)?
- What is the max bus speed that could be achieved this way? What is a safe address space not covered by any of the stix?
Yes, and right now using nCS4 address space is being left aside for such a purpose. Bus speed ranges across the entire span that the PXA can use. The default 100 MHz.
Does gumstix interface to a touch screen?
Yes, the Audiostix2 expansion board provides the I/O required to use the UCB1400 Touch Screen Interface.
