At my side this command doesn’t work properly without sudo: all addresses are ‘0’, but once with sudo, it becomes Ok.

The comment below the code isn't quite accurate … rather "ORing 0" (e.g. | (0 << 21) isn't necessary …

I just got the Raspberry Pi 3B, and plan to go through your book to familiarize myself with the capabilities and uses of the device. Do you recommend installing Stretch or Jesse as the better platform for the code examples in the book, or are both equally compatible?

Best Regards,
Jim

As of the November 2016 release, Raspbian has the SSH server disabled by default. You might want to add information around page 30 to tell new users how to enable ssh. Refer to the following link. Great book by the way!

https://www.raspberrypi.org/documentation/remote-access/ssh/

The only downside is that I am having problems with the examples that access the GPIO in C.

As an example, the makeLED programme in Ch05, which fails to compile under C at line 38; reporting ” makeLED.c:38:7: warning: implicit declaration of function ‘usleep’ [-Wimplicit-function-declaration] usleep(100000); // sleep for 100ms. requiring the inclusion of to allow compilation.

Even then the program fails to run reporting “segmentation faults”; such as on line 48 “writeGPIO(GPIO4_PATH “value”, “1”);”

I assume that my issues surround the programming differences between the various RPi’s; personally I am using an RPi 3, running Raspbian Version 9 (“Stretch”).

In an endeavour to fully progress through your book, could you confirm which RPi and software the book was actually used for testing the programmes?

My aim is then to configure an identical RPi, to complete the book and then explore the GPIO programming across the versions.

I must confess that it is this variety of GPIO configurations that is confusing me, (and probably many other readers) and any help would be welcome.

Thank you in anticipation.

Roger King

make oldconfig

This defaults all questions based on the contents of your existing ./.config file and asks about new config symbols. I gather if the new symbol questions aren’t answered correctly this leads to building an incompatible hello.ko, hence the error message when loading. I used the following instead:

make defconfig

Which worked. If you enter the linux-rpi-4.9.y directory there is a README file. Starting at line 146 you’ll see all the make options. In the newer linux version I was unable to find (in /proc) the .config or config.gz files. I gather this has changed since 4.1.12-v7+ Also when assigning KHEADER=’pwd’ you’ll want to use KHEADER=$(pwd) Same for the ‘uname -r’ Use $(uname -r) instead. Otherwise all is well. Hope this helps a few out there.

insmod: ERROR: could not insert module hello.ko: Invalid module format

The kernel I’m running is: Linux raspberrypi 4.9.57-v7+ #1045 SMP Fri Oct 20 11:44:49 BST 2017 armv7l GNU/Linux (per uname -a)

The source I downloaded is linux-rpi-4.9.y I’m thinking this is an incompatible version problem? But the source and current kernel appear to be the same. Confusing.

Can you please provide any suggestions. Perhaps others have encountered this problem. Many thanks – Scott

Regards
Viveka N