Raspberry Pi Forums

Hello.

Before I buy a R-Pi, I want to know if it can do what I need.

All I want is to read the fully detailed documentation of the GPIO. Hardware side (how the output have been designed, if they are tristate or not, high impedance, pin count, available features, and ... how to control them from Linux. For example, I know that good quality bit forging in almost impossible under Linux due to the poor Linux VM (many things work way better under DOS; example, it's impossible under Linux to generate PWN at a rate higher than the VM rate; while DOS granilosity can come down to the bus freq !!! )

I personally find the legacy parallel port on PC pretty much complex to use to play with relays; and sound card is usually the best analog input. And computers hardly have analog outputs.

I want to know what can be done with the GPIO at hardware side, and how complex it is at software side.

- digital vs analog

- inputs and outputs

- pin count

- features for each pin

I did not find any doc on this website; so, I will probably need a user to email me the CD content.

Finaly, who has stock in Europe (France) ? The french Farnell says to be out of stock.

Thanks

Documentation for the RasPi is still a work in progress. Here is something to get you started learning about the available GPIO pins, including the pinout description and some sample I/O code:

http://elinux.org/Rpi_Low-leve.....eripherals

You may also find the Broadcom SoC documentation useful: http://www.raspberrypi.org/wp-.....herals.pdf

also these notes: http://www.raspberrypi.org/for.....ins/page-3

Briefly, there are a total of 26 pins (2x13 header, 0.100" spacing) including 5V, 3.3V, Ground, and 17 GPIO lines. Current drive is programmable 2 mA up to 16 mA. All 17 can be used as general-purpose I/O (3.3V logic level inputs or outputs, NOT 5V tolerant). Or you can use various dedicated functions on specific pins including UART, SPI, I2C. There are also two PWM signals from the SoC that are used for audio output, which could be repurposed if you do some soldering. Otherwise the RasPi is a completely digital board, with no A/D or D/A available.  If you need hard real-time control functions, your easiest solution is to use an Arduino or similar, and interface that to the RasPi if needed. In fact one RasPi accessory interface board, the "Gertboard" includes just such a feature. http://www.raspberrypi.org/archives/868

Finally, there are only two licensed distributors and there is no stock. There is a waiting list with about 350000 orders we are told; volume manufacturing in progress, backlogs should clear by end of Summer (?)

Furthermore, I would not place any GPIO stuff under absolute beginners. Using GPIO falls more under intermediate.

http://elinux.org/Rpi_Low-leve.....eripherals is what I needed to know. Now, I will place an order. Thanks.