XO-4 Touch

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This page still under development --- please excuse any errors --9/22/2012

The XO-4 laptop is the latest refresh of the XO laptop. It is available in two models: XO-4 and XO-4 Touch, with the latter providing multi-touch input on the display. Like the XO-1.75, it uses an ARM processor to provide high performance with low power consumption, while keeping the industrial design and batteries of the XO-1.

XO-4 laptops ship with a new software release based on Fedora 17, including both Sugar and GNOME software.

Identification

XO-1.75 siblings.jpg

The XO-4 laptops will be identified by a unique set of dots on both sides of the hinge cover. XO-4 Touch units have a slightly deeper (1mm) bezel around the display.

Specifications

Drawing75c1.jpg
Dimensioned Drawing of XO, click to enlarge

The definitive XO-4 laptop specification is only available in PDF form ("CL4" is the model identifier in the manufacturing data for the XO-4 and XO-4 Touch hardware).

The specs below are not authoritative, please refer to the PDF version of the spec linked above.

Physical dimensions

  • Approximate dimensions: 245mm × 230mm × 30.5mm (see drawing to the right for detailed dimensions)
  • Approximate weight
    • with LiFePO4 battery: 1.36KG (~3lbs);
    • with NiMH battery: 1.58KG (~3.48lbs);
  • Configuration: Convertible laptop with pivoting, reversible muti-touch enabled display; dirt- and moisture-resistant system enclosure; no fan.

Core electronics

Prototype Motherboard

XO-4 is designed around the Marvell PXA2128 system on a chip.

  • CPU: dual Marvell PJ4 ARM cores;
    • CPU clock speed: 1 GHz (superscalar and out-of-order instruction execution);
    • ARM instruction set compatible (including Thumb-2 and Wireless MMX2);
    • ARMv7 architecture compatible;
    • 32 KB L1 I-cache and 32 KB L1 D-cache per processor, shared 512KB L2 cache;
  • The PXA2128 includes hardware video encode/decode, a Vivante GC2000 3D graphics engine, display controller, USB, SDIO, and other system interface and management functions
  • DRAM memory: 1GB or 2GB DDR3 dynamic RAM;
  • Mass storage: 4 GiB or 8GiB NAND flash in an eMMC device soldered to the motherboard.
    • an internal microSD card slot for repair/replacement -- requires soldering the microSD bracket;
    • externally accessible full-size SD card slot;
    • No rotating media.
Green-and-white-e-book.jpg

Display

Main article: Display
  • Liquid-crystal display: 7.5” dual-mode TFT display;
  • Viewing area: 152.4 mm × 114.3 mm;
  • Two "modes" depending on lighting conditions:
(1) Grayscale (B&W) reflective mode: for outdoor use—sunlight-readable; primarily lit from the front by ambient light; high-resolution (200 DPI), 1200(H) × 900(V) grayscale pixels; power consumption 0.1–0.2Watts;
(2) Color, backlight mode: for indoor use; primarily lit from behind by the LED backlight; built in sub-pixel sampling of the displayed color information results in a perceived resolution of approximately 984(H) × 738(V); power consumption 0.2–1.0Watts;
Note: web browser images are currently scaled up so that an image of very roughly [800 × 600] fills up the browser window.

Touchscreen

The XO-4 Touch has the ability to sense/track two simultaneous touches of the display. In order to provide this functionality without degrading the performance of the display in direct sunlight, an infrared touchscreen technology from Neonode is used. This technology is also capable of sensing/tracking any stylus with a diameter larger than 8mm. To avoid damaging the surface of the display, it is recommended that the stylus have a relatively soft tip.

eBook Reader

The screen can pivot and folded backwards so the XO-4 Touch becomes a tablet or eBook reader. Several buttons on the frame offer different modes of paging, scrolling, etc.

Integrated peripherals

  • Keyboard: 80+ keys, 1.0mm stroke; sealed rubber-membrane key-switch assembly;
Improved Membrane Keyboard
  • Gamepad: Two sets of four-direction cursor-control keys;
  • Touchpad: Capacitance touchpad
  • Audio: Internal stereo speakers and amplifier; internal monophonic microphone; jacks for stereo external headphones and microphones.
    • Realtek ALC5631 audio codec (I2S)
  • Camera: integrated color video camera; 640 x 480 resolution at 30 FPS;
    • Independent (and undefeatable by software) display of microphone and camera recording status;
    • The camera and device driver support disabling AGC and automatic color balancing, to enable its use as a photometric sensor for educational applications;
    • Omnivision OV7670
  • Wireless Networking: Integrated 802.11b/g (2.4GHz) interface; dual adjustable, rotating antennas;
    • Marvell 88w8686 WLAN module, with SDIO interface, on removable module;
    • Remains powered while the laptop suspends, waking the laptop if a packet addressed to it arrives.
    • Ad-hoc networking and 802.11s mesh support available
  • Accelerometer: ST LIS3DH three axis accelerometer (data sheet (PDF))
  • Status indicators:
    • Power, battery, Wi-Fi, one software controlled (intended for onboard flash access), visible with lid open or closed;
    • Microphone In-Use, and Camera In-Use, visible when lid is open.
    • Light Sensor: a reverse biased LED.

External connectors

  • DC power: 6mm (1.65mm center pin) connector; 11 to 24 V input usable, –32 to +40V input tolerated; power draw limited to 25 W; - see power connector dimensions at Battery and power.
    • Maximum Power Point Tracking alters voltage/current for maximum battery-charging power from solar panels
  • Headphone output: standard 3.5mm 3-pin switched stereo audio jack;
  • Microphone input: standard 3.5mm 3-pin switched stereo microphone jack; selectable 2V DC bias; selectable sensor-input mode (DC or AC coupled);
  • USB: Two Type-A USB 2.0 connectors; Up to 1A power supplied (total, available through a single connector);
  • HDMI: A micro-HDMI connector is provided, supporting video output
  • Flash Expansion: full-size SD Card slot.
Connectors

Battery

  • Pack type: 2 or 4 cells LiFePO4; or 5 cells NiMH, approx. 6V series configuration;
  • Capacity: 2800 mAh (LiFePO4) or 3000 mAh (NiMH)
  • Fully-enclosed “hard” case; user removable;
  • Electronics integrated with the pack provide:
    • Identification;
    • Battery charge and capacity monitoring chip (Maxim DS2756 data sheet);
    • Thermal and over-current sensors along with cutoff switch to protect battery;
  • Minimum 2,000 charge/discharge cycles (to 50% capacity of new).

See Laptop Batteries or more information.

BIOS/loader

On XO-4, there are two different firmwares installed:

  • A small bootloader written in Forth and interpreted by CForth runs on the security processor (a small ARM core in the PXA2128)
  • Open Firmware runs on the main (PJ4) processor

The bootloader run by the CForth interpreter on the security processor is responsible for initializing the SoC pins and the main memory. It then loads Open Firmware into main memory and starts it executing on the main processor. This CForth bootloader then continues to execute on the security processor, processing input from the keyboard and touchpad.

Open Firmware (OFW) initializes the system peripherals, then loads the OS kernel into memory and starts executing it. OFW also includes hardware diagnostics.

  • A dedicated 2 MiB SPI-interface flash ROM contains both CForth (first 128KB) and OFW;
  • Hardware support is provided to prevent reprogramming of the OFW flash ROM by malicious software;

Environmental specifications

  • Temperature: 0 to 50 degrees Celsius (operating); -20 to 60 degrees Celsius (non-operating)
  • Humidity: UL certification planned to IP42 when closed, the unit should seal well enough that children walking to and from school need not fear rainstorms and dust;
  • Maximum altitude: –15m to 3048m (14.7 to 10.1 PSIA) (operating), –15m to 12192m (14.7 to 4.4 PSIA) (non-operating);
  • Shock 125g, 2ms, half-sine (operating) 200g, 2ms, half-sine (non-operating);
  • Random vibration: 0.75g zero-to-peak, 10Hz to 500Hz, 0.25 oct/min sweep rate (operating); 1.5g zero-to-peak, 10Hz to 500Hz, 0.5 oct/min sweep rate (nonoperating);
  • 2-3mm plastic walls (1.3mm is typical for most systems).

Regulatory requirements

  • The usual US and EU EMI/EMC (electromagnetic-interference and electromagnetic-compatibility) requirements;
  • The laptop meets IEC 60950-1, EN 60950-1, and CSA/UL 60950-1 (safety) specifications. It also complies with UL 1310 and UL 498. In order to guarantee the safety of children using the laptop, it passes ASTM F 963 (Standard Consumer Safety Specification on Toy Safety, 2003 edition);
  • The external power adapter complies with IEC, EN, and CSA/UL 60950-1;
  • The removable battery pack complies with IEC, EN, and CSA/UL 60950-1 and UL 2054;
  • RoHS (Restriction of Hazardous Substances Directive – EU) compliant.

Block Diagram

XO 4 Block Diagram.png

Software

There are three distinct pieces of software on the XO-4:

OpenFirmware automatically upgrades the EC firmware at boot time, if the installed version is older than the version included in OpenFirmware. The laptop must have both a charged battery and external power supplied at boot time for this to happen.

As usual, the operating system image automatically upgrades OpenFirmware if necessary.

Upgrading OFW

XO-4 laptops use Q7yxx firmware releases. These will not work on an XO-1, XO-1.5, or XO-1.75. The current firmware release for XO-4 can be found at Firmware#XO-4.

To upgrade the version of Open Firmware, place a recent release of the Q7XYY firmware onto an SD device, and place it in the external SD slot, or on a USB drive.

Interrupt the Open Firmware (OFW) boot process by pressing the ESC key.

Type: 

 flash ext:\q7XYY.rom

Or for a USB drive: 

 flash u:\q7XYY.rom

The laptop will automatically reboot.

If you need to do this to a bare motherboard, you can use the flash! command which skips the tests for two sources of power.

If the version of OFW installed on the laptop isn't working, you might be able to upgrade it using CForth or using JTAG.

Upgrading EC

This is now done automatically by OpenFirmware.

However, if you need to do it manually ... download the latest EC code from: http://dev.laptop.org/pub/ec/. It should be prefixed by "cl4" (e.g. cl4-7.0.2.02.img). Place this file on a USB drive or SD card, and insert it into the laptop being reprogrammed.

From OpenFirmware, type: 

 flash-ec u:\your_filename.img

If you need to do this to a bare motherboard, you can use the flash-ec! command which skips the tests for two sources of power.

Upgrading Linux

Linux images for the XO-4 are not currently available in a sane location.

Installing from OpenFirmware using USB

You will need the .zd version of the OS image. Download it, then:

  1. Place the image on a USB stick, and insert it into any of the XO-4 laptop's USB ports.
  2. Get the Ok prompt,
  3. Install onto the internal SD card, by typing:
fs-update u:\21022xx2.zd

Installing from OpenFirmware using SD card

You will need the .zd version of the OS image. Download it, then:

  1. Place the image on an SD card, and insert it into the XO-4 laptop's external SD slot.
  2. Get the Ok prompt,
  3. Install onto the internal SD card, by typing:
fs-update ext:\21022xx2.zd

Installing from Linux using an earlier XO

To install on an XO-1.5/1.75, boot the XO to Linux, insert the SD card in the XO's external slot, then: 

zcat os19.img.gz > /dev/mmcblk1

... and then power down, remove the SD card, and insert it in the XO-4.

Installing from OpenFirmware using an earlier XO

You will need the .zd version of the OS image. Download it, then:

  1. Place the image on a USB stick, and insert it into the XO laptop's USB port.
  2. Get the Ok prompt,
  3. To install onto the external SD card, type:
devalias fsdisk ext:0
fs-update u:\os41.zd

... and then power down, remove the SD card, and insert it in the XO-4.

Software Restrictions

See Trac.

More Information

Serial Adapter

Third generation serial adapter.

For firmware, operating system and kernel debugging a serial adapter is required. We are using our third generation serial adapter with the XO-4, which has 3.3V serial on the target side, and a USB B socket on the host side.

Location of serial port

(it is in the same location as on an XO-1.75).

To use the serial port, disassemble the laptop (instructions) and connect the serial adapter to the motherboard using the at the point shown. The heat spreader does not have to be removed.

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