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About the Pi and the par port..... some things that work here, my first posting here...t

Here I use the Pi as a remote JTAG programmer to program xilinx FPGA board via the parport:

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Here I use the Pi as PIC18F programmer to drive the parport 'noppp' PIC programmer:

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Basically I think that if only 5V for input available is you can simply attenuate that with 2 resistors, If 5V output is required you can use most 74HTC chips (buffers, AND gates, xor gates, whatever you have around) as level converter 3.3V to 5V. Also I have GPS working on the Pi via USB to serial adaptor, but could also be directly on the GPIO without MAX232 (have not tried that yet), I wrote this software for GPS:

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It also does SPC01 altitude and magnetic heading, and MPU6050 accelerometer and gyro too, but as this is for model airplane I am rewriting it all in PIC asm, PIC uses a lot less current and is a lot lighter.

And I have openelec on it playing 720 progressive HD video recorded from satellite.

So far I am happy with the Pi:-)

Reply to
Jan Panteltje
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========== Your published info in excellent! These days I've only got access to a DMM and solder iron: for the ParPort cable's ends to a rPi header-socket. No PCB & ICs please. == So since the parallel port is Centronics based, it would be TTL compatible; and as I remember the TTL thresholds are centered below 2.5V. So the rPi's 3.3V output should be able to drive the parallel port's inputs. == Is that right?

==TIA.

Reply to
Unknown

Why do you keep calling it a ParPort? It's not a parallel printer port. These days computers have General Purpose Input Output ports - aka GPIO.

The Pi's GPIO is not capable of printing (well, not unless someone wants to write a printer driver for it and do the voltage level switching)

No.

It's not a "parallel port" and it's not Centronics based.

The Pi has 17 GPIO pins. 8 of these are general purpose. 1 of these

8 can be re-provisioned to drive a hardware derived clock and another of these can be re-provisioned to drive a hardware derived PWM. Of the remaining: they can be used for general purpose digital inputs/outputs, or: 2 can be switched to I2C mode, 2 can be used for serial (uart), 5 can be used for a 2 port SPI master.

Rev 2 Pi's have an second GPIO connector with 4 more GPIO pins.

As well as power (+5, +3.3) and ground.

Want some C software to drive it? Start here:

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Pin-outs, etc.

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As well as millions of other pages online.

The Pi's 3.3v outputs will generally drive 5v TTL devices - they can source or sink 16mA.

Example of the Pi driving a 5V device:

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However if you send 5v into the Pi's GPIO pins, then it's bye bye Raspberry Pi...

Gordon

Reply to
Gordon Henderson

On a sunny day (Wed, 10 Apr 2013 06:39:45 +0000 (UTC)) it happened Unknown wrote in :

Thank you.

Yes I think that is correct. Actually I measured the voltage levels on my PC motherboard par port, and most were 3.3V. It may just be the PC motherboard is simply 5 V tolerant 3.3 V logic.. YMMV. It is simple to write some code to toggle PC par port pins and measure what comes out with a DVM. It is usually address 0x378 (data) and 0x379 (control) on the PC.

The other way around you need to, if the PC indeed outputs 5V, use buffers on some attenuator. If the port needs to be birirectional than you need some more complicated buffering. I think there are few par port printers left these days (but I still have one), driving such a printer would need writing drivers (user space) or a kernel module, plus some electronics.

As you state 'No PCB and ICs' I suggest you get an USB printer :-)

Reply to
Jan Panteltje

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