Talk:RPi Low-level peripherals - Revision history

Wmat: /* Example code section should be split to another page */

2013-02-02T01:30:36Z

‎Example code section should be split to another page

Unkle george: /* Example code section should be split to another page */ new section

2013-02-01T22:31:18Z

‎Example code section should be split to another page: new section

Cnt: /* GPIO C driving example */

2013-01-04T07:16:49Z

‎GPIO C driving example

Jamesmiller5: /* GPIO C driving example */

2013-01-01T17:53:34Z

‎GPIO C driving example

Pijyoi: /* GPIO C driving example */ new section

2012-09-08T01:52:18Z

‎GPIO C driving example: new section

Grumpy Mike at 17:51, 29 August 2012

2012-08-29T17:51:21Z

Grumpy Mike: Added comment on proposed new diagram.

2012-08-29T17:50:21Z

Added comment on proposed new diagram.

Danpeirce at 18:54, 20 August 2012

2012-08-20T18:54:09Z

Danpeirce at 18:44, 20 August 2012

2012-08-20T18:44:15Z

Danpeirce at 18:41, 20 August 2012

2012-08-20T18:41:09Z

← Older revision		Revision as of 01:30, 2 February 2013
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	All the examples are great, but they clutter the page and can be a bit overwhelming. I suggest moving them to their own page and replacing them here with a section explaining the different methods of accessing external I/O.		All the examples are great, but they clutter the page and can be a bit overwhelming. I suggest moving them to their own page and replacing them here with a section explaining the different methods of accessing external I/O.
		+
		+	Feel free to make that happen. --[[User:Wmat\|Wmat]] ([[User talk:Wmat\|talk]]) 01:30, 2 February 2013 (UTC)

	==Methods of writing to external I/O==		==Methods of writing to external I/O==

← Older revision		Revision as of 22:31, 1 February 2013
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	Thank you for fixing that! I noticed the same thing and came back here to fix it.		Thank you for fixing that! I noticed the same thing and came back here to fix it.
		+
		+	== Example code section should be split to another page ==
		+
		+	All the examples are great, but they clutter the page and can be a bit overwhelming. I suggest moving them to their own page and replacing them here with a section explaining the different methods of accessing external I/O.
		+
		+	==Methods of writing to external I/O==
		+	;1. Directly write to the memory mapped control registers from your application.
		+	*Pro's / Cons of this approach
		+	*Link to C mmap example
		+	*Links to libraries that use this method.
		+	**WiringPi https://github.com/WiringPi/WiringPi
		+	**BCM2835 C library http://www.open.com.au/mikem/bcm2835/
		+	**Quick2wire https://github.com/quick2wire/quick2wire-python-api
		+	;2. Use the provided driver a control the I/O pins with the Linux kernel /sys/class interface.
		+	*Link to http://www.kernel.org/doc/Documentation/gpio.txt
		+	*Directions how to enable the kernel module in Raspian
		+	*Link to bash script to export gpio pin

← Older revision		Revision as of 07:16, 4 January 2013
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	: I've updated the C code example with your suggestions,a pruning of unnecessary includes and compilation with `gcc -Wall gpio.c` fixing a minor cast error. Code has been tested on a Raspberry Pi and seems to work fine. --[[User:Jamesmiller5\|Jamesmiller5]] ([[User talk:Jamesmiller5\|talk]]) 17:53, 1 January 2013 (UTC)		: I've updated the C code example with your suggestions,a pruning of unnecessary includes and compilation with `gcc -Wall gpio.c` fixing a minor cast error. Code has been tested on a Raspberry Pi and seems to work fine. --[[User:Jamesmiller5\|Jamesmiller5]] ([[User talk:Jamesmiller5\|talk]]) 17:53, 1 January 2013 (UTC)
		+
		+	Thank you for fixing that! I noticed the same thing and came back here to fix it.

← Older revision		Revision as of 17:53, 1 January 2013
Line 108:		Line 108:

	} // setup_io		} // setup_io
		+
		+	: I've updated the C code example with your suggestions,a pruning of unnecessary includes and compilation with `gcc -Wall gpio.c` fixing a minor cast error. Code has been tested on a Raspberry Pi and seems to work fine. --[[User:Jamesmiller5\|Jamesmiller5]] ([[User talk:Jamesmiller5\|talk]]) 17:53, 1 January 2013 (UTC)

← Older revision		Revision as of 01:52, 8 September 2012
Line 65:		Line 65:
	That diagram is OK apart from the line that says "The Alt 0 function is defined at boot time" It is not!		That diagram is OK apart from the line that says "The Alt 0 function is defined at boot time" It is not!
	--[[user:Grumpy Mike\|Grumpy Mike]] 18:49 28 August 2012 (UTC)		--[[user:Grumpy Mike\|Grumpy Mike]] 18:49 28 August 2012 (UTC)
		+
		+	== GPIO C driving example ==
		+
		+	There are quite a few examples found on the web showing memory access using /dev/mem but with the same error of allocating a block of (page-aligned) user memory to pass as the 1st parameter to mmap().
		+
		+	setup_io() could be rewritten as follows:
		+
		+	//
		+	// Set up a memory regions to access GPIO
		+	//
		+
		+	void setup_io()
		+	{
		+	/* open /dev/mem */
		+	if ((mem_fd = open("/dev/mem", O_RDWR\|O_SYNC) ) < 0) {
		+	printf("can't open /dev/mem \n");
		+	exit (-1);
		+	}
		+
		+	/* mmap GPIO */
		+
		+	// Now map it
		+	gpio_map = (unsigned char *)mmap(
		+	NULL, // was (caddr_t)gpio_mem,
		+	BLOCK_SIZE,
		+	PROT_READ\|PROT_WRITE,
		+	MAP_SHARED, // was MAP_SHARED\|MAP_FIXED,
		+	mem_fd,
		+	GPIO_BASE
		+	);
		+
		+	close(mem_fd); // no need to keep fd open after mmap
		+
		+	if ((long)gpio_map < 0) {
		+	printf("mmap error %d\n", (int)gpio_map);
		+	exit (-1);
		+	}
		+
		+	// Always use volatile pointer!
		+	gpio = (volatile unsigned *)gpio_map;
		+
		+
		+	} // setup_io

← Older revision		Revision as of 17:51, 29 August 2012
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	That diagram is OK apart from the line that says "The Alt 0 function is defined at boot time" It is not!		That diagram is OK apart from the line that says "The Alt 0 function is defined at boot time" It is not!
		+	--[[user:Grumpy Mike\|Grumpy Mike]] 18:49 28 August 2012 (UTC)

← Older revision		Revision as of 17:50, 29 August 2012
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	--[[user:danpeirce\|danpeirce]] 18:49 20 August 2012 (UTC)		--[[user:danpeirce\|danpeirce]] 18:49 20 August 2012 (UTC)
		+
		+	That diagram is OK apart from the line that says "The Alt 0 function is defined at boot time" It is not!

@@ Line 54: / Line 54: @@
 ----
-I can't recall seeing designations like top row, bottom row, left and right on a pinout for a connector. This would be because there is much ambiguity (in general) about which of the four sides of the board should be top. More typically everything is referenced relative to a key like the pad for PIN 1. Since the connector is at the board edge there could be a great deal more clarity for the novice if the board edge were marked in the diagram. I notice now that if I click on the source link under the pin diagram I am taken to another diagram that actually includes enough of the board that it is clear which row is at the board edge. For novice users I suggest adding a photo with superimposed pin numbers. The photo should show the corner of the board containing the connector and nearby parts.
+I can't recall seeing designations like top row, bottom row, left and right on a pinout for a connector. This would be because there is much ambiguity (in general) about which of the four sides of the board should be top (more typically top would refer to the through hole component side of the board). More typically everything is referenced relative to a key like the pad for PIN 1. Since the connector is at the board edge there could be a great deal more clarity for the novice if the board edge were marked in the diagram. I notice now that if I click on the source link under the pin diagram I am taken to another diagram that actually includes enough of the board that it is clear which row is at the board edge. For novice users I suggest adding a photo with superimposed pin numbers. The photo should show the corner of the board containing the connector and nearby parts.
 --[[user:danpeirce|danpeirce]] 9:49 20 August 2012 (UTC)
@@ Line 60: / Line 60: @@
 I'm thinking something like this could be useful (I combined part of an RPi image from this site File:RPi-Front-JPB.jpg) with the pin information on this page.
 see http://danpeirce.net46.net/dokuwiki/lib/exe/detail.php?id=raspberry_pi&media=rpi:gpio_pins.png
 --[[user:danpeirce|danpeirce]] 18:49 20 August 2012 (UTC)

← Older revision		Revision as of 18:41, 20 August 2012
Line 56:		Line 56:
	I can't recall seeing designations like top row, bottom row, left and right on a pinout for a connector. This would be because there is much ambiguity (in general) about which of the four sides of the board should be top. More typically everything is referenced relative to a key like the pad for PIN 1. Since the connector is at the board edge there could be a great deal more clarity for the novice if the board edge were marked in the diagram. I notice now that if I click on the source link under the pin diagram I am taken to another diagram that actually includes enough of the board that it is clear which row is at the board edge. For novice users I suggest adding a photo with superimposed pin numbers. The photo should show the corner of the board containing the connector and nearby parts.		I can't recall seeing designations like top row, bottom row, left and right on a pinout for a connector. This would be because there is much ambiguity (in general) about which of the four sides of the board should be top. More typically everything is referenced relative to a key like the pad for PIN 1. Since the connector is at the board edge there could be a great deal more clarity for the novice if the board edge were marked in the diagram. I notice now that if I click on the source link under the pin diagram I am taken to another diagram that actually includes enough of the board that it is clear which row is at the board edge. For novice users I suggest adding a photo with superimposed pin numbers. The photo should show the corner of the board containing the connector and nearby parts.
	--[[user:danpeirce\|danpeirce]] 9:49 20 August 2012 (UTC)		--[[user:danpeirce\|danpeirce]] 9:49 20 August 2012 (UTC)
		+	I'm thinking something like this could be useful (I combined part of an RPi image from this site File:RPi-Front-JPB.jpg) with the pin information on this page.
		+	see [[http://danpeirce.net46.net/dokuwiki/lib/exe/detail.php?id=raspberry_pi&media=rpi:gpio_pins.png]]
		+	--[[user:danpeirce\|danpeirce]] 18:49 20 August 2012 (UTC)