USB peripherals

AD/DA & "Parallel" interfaces

Precisely for these types of ideas the computer needs some sort of basic A/D, D/A and suitably protected bi-directional "parallel" type interfaces. These need to be built-in so their use doessn't add wire spaghetti, cables/conversion boxes don't get lost, is "fumble free" and always available. In short, it must be simple, empowering and an idea generating catalyst. L Pfeffer March 20, 2006

• Or perhaps these miscellaneous fun things should all be available on a USB interface. It would keep it very expandaple, yet low base cost. USB devices keep getting less expensive to develop. --imajeff

Serial Port??

I know it can be done thru USB emulators... but serial ports are simple and easy to use. If someone wants to make some electronic project, or using old hardware (mouse, or serial comunications devices), it could be useful to have one.

it's just an idea, but I started making my first hardware projects with this, and even today is cheaper (at least here in Argentina) and easy to make serial ports working hardware (rather than buying PICs and programming them).

And still many hardware has serial ports (networking devices for example).

Gandolfi

Serial ports are NOT robust, at least nine tiny little pins that it's very easy to bend or break, not a good idea. Perhaps with a more robust connector, though IME the parallel port was more useful for electronics projects. 62.252.0.11 16:02, 17 March 2006 (EST)

The photos from the developer boards show an external RS232 level shifter circuit attached (to some GPIO pins?). Legacy serial/parallel ports are nice for experimenting, there's IMHO no need for this for a laptop which is targeted at 6-12yo childs.

Not to mention the fact that there IS NO OLD HARDWARE in these 3rd world villages. It would be far better to have an external power plug with circuit breaker switch so that people could use the old bananas they have laying around TO MAKE BATTERIES!!! The kids will be motivated to find a way to pedal less so lets help them learn some science.

More RAM

Its Flash memory can be expanded easily and cheaply by plugging in USB thumb drives for any user who needs one. Thus, if you have a chance to add a little more memory to the base unit, add a RAM chip, not a Flash chip!

I agree with this point... maybe the laptop should have a free slot to allow increase of ram ?? (at least is the possibility to add ram) that shouldn't be that much increase of costs...

But if the case can be easily opened to insert RAM won't this make it easier for dirt and moisture to enter too? 62.252.0.11 16:14, 17 March 2006 (EST)

usb vs built-in flash

Question: What's the relative access speed of USB2 thumb drives versus the built-in flash memory?

The cheap solution to adding flash might be an under-lid USB2 port with a cut-out that lets you leave a flash device in-place when the laptop closes. This would not solve the RAM issue (as you don't want to swap to the flash), but it might be the lowest-cost way to give convenient storage expansion.

As the USB flash would be under the lid when the lid was closed, it would need to be in a recess to avoid hitting the screen or bevel. A 9x24x45 (DxWxL) mm recess will hold the popular smaller sticks while a 12x35x70 mm recess should hold even the largest USB sticks. Next to the touchpad, or along the top edge of the keyboard, or under the d-pad & speaker are all good locations.

USB Hard Drive

In the other hand, as John said, a USB thumb or hard drive, could be easily plugged. These devices currently start around 80 (USD) and 40 Gb. They are not 100% reliable when running of an underpowered USB port or an underpowered USB hub. Some manufactures slow down the drives to make them use less power. No budget USB2 drive could be considered a reliable, rugged, and robust companion to the OLPC PC.

One reason to consider the hard drive option would be to give the device an appropriate device to use for swap space. On the other hand, this may not be possible as the device would not be connected at boot/resume.

Note of course: A hard drive can easily be added by plugging one into USB2 as well. One catch is that rugged, properly cooled USB2 hard drives do not seem to exist at any reasonable price. Another catch is power.

--John Gilmore

About the power of an external hard drive, I think if someone has money to buy it, it probably has electricity, so it's a matter of designing an external hard drive with with external power (or rechargeable batteries), if not, USB thumbs seems a good option, and they're getting cheaper.

Gandolfi

I understand there are 2.5inch hard disks that take a peak current of 600mA (at 5v) but thier average consumption is less than half that. I always though this would be a good spot for a rechargable battery. 62.252.0.11 16:14, 17 March 2006 (EST)

Keyboard Illumination

It is not necessary to illuminate the keyboard if fire is available in the target area. However, if the kids are willing to do the extra pedalling to provide light, there are nice cheap USB-powered LED lights available. This makes a lot more economic sense than burdening every device with illumination by building it into the keyboard.

GPS option (through hole device, unpopulated)

GPS receivers with volume of about 1 cm^3 and a power consumption of less than 100mW (while continuously tracking!) are available today. These devices will provide a very high additional value for a small fraction of users.

Please evaluate the implications of reserving about 4 cm^2 PCB space for a through hole (not SMD) mountable GPS module (using bit-banged serial IO via general purpose IO pins, and the GPS module being not end-user mountable).

Note that the target users don't need GPS to know where they are. If GPS was needed for a classroom situation or for some school project (mapping the fields around the village) then the OLPC already supports GPS through USB. Either a GPS that emits NMEA through RS-232 connected to a USB-serial port or a Bluetooth GPS that talks to a USB-Bluetooth dongle.

USB ports are there for a VERY good reason

Networking

USB2

The USB2 interface hardware allows one of the USB ports to be used as a device port as well as a host port. This means that with the proper cable and software, two laptops could be plugged together and you could network them via USB2. They can be daisy-chained in the same way, and should provide ~20 Mbytes/sec of thruput (see GNU Radio USRP software for Linux software that can keep the USB2 bus moving data at maximum speed). There's USB device software in the Sharp Zaurus, which runs Linux and has such a dual-use USB port (USB 1.1 though).

A USB2 cable is much faster than the wireless, and cheaper than adding USB2 ethernet cards + hubs + cables + etc. Running IP, DHCP, and Rendezvous over USB shouldn't be hard; I'm a little surprised it isn't standardized already (like IP over Firewire).

--John Gilmore

This is usb-on-the-go and needs the 5-pin tiny connector not the 4-pin normal sized ones because according to the designers it's only useful for PDAs and cameras not real PCs. Scheesh! 62.252.0.11 17:20, 17 March 2006 (EST)

Also USB has alot of overhad associated with which slows it down and you need the a cable, which is limited to 5m (absolute maximum see if you can find one that longer much less someone in Africa). The wireless appears to have very high range and as it is a/g wireless they should be able to combine the two frequencies for 100Mbit/s which is only 4x slower than usb so not a big deal. Even if you don't use both a and g together and only get 50Mbit/s you can transfer 512Mbytes all the memory on the computer in 73 seconds. Thats plenty fast Lotu