Comments on: Chapter 6: Interfacing to the Raspberry Pi Input/Outputs

By: Victor

Victor — Tue, 24 Apr 2018 19:04:06 +0000

Is it possible to reset the GPIO port to its original state without having to reset the pasperry? Is there any command for it?

es posible restablecer el puerto GPIO a su estado original sin tener que restablecer la pasperry? existe algún comando para ello?

By: Sud

Sud — Mon, 15 Jan 2018 21:46:59 +0000

Hi Derek,
I’m having have a good time pass with the book and physical computing. Thank you !
I have some issue with the expample fadeLED.cpp (chap 06). When I executed the code (downloaded from github), the LED went on and repeatedly (3 or 4 times) I lost my network connection so I couldn’t shutdown gracefully. Hence I had to restart my RPi. On retrying it said something like /sys/class/gpio/gpio27 couldn’t not be found and subsequently I couldn’t run commands like ls or sudo shutdown. I followed the connections as in figure 6-20 b. Now couple of questions 1. what could have possibly gone wrong, 2. if something like this happens how do I shutdown my RPi gracefully.
Any help or pointers is really appreicated.

By: Jeff Gros

Jeff Gros — Mon, 02 Oct 2017 03:25:26 +0000

A few notes:

I can confirm Craig’s issue with needing sudo for pwm.cpp.

For anyone struggling to have your temperature sensor in dht.cpp give you data, I found that when I measured the pulses with my scope they were much longer. 26 us for low and 68 us for high. I followed Derek’s lead and used the average of 46. This gave me much better results. For reference, I’m using AM2302.

Also, lartmaker.nl is no longer online, but you can still download the file from the web archive.

By: admin

admin — Sun, 11 Jun 2017 19:27:01 +0000

Hi there, is your SD card in read-only mode? Some of them have a switch on the side of the card. Kind regards, Derek.

By: Nishand

Nishand — Mon, 22 May 2017 05:50:12 +0000

Does anyone know why I can’t save a file in raspberry Pi? I was trying to write my own C++ code. As long as the raspberry pi is On, I can access the file, work on it. But as soon as I reboot the raspberry Pi, the file disappears. I tried saving the file in all of the folders – Documents, Templates, Desktop, Downloads, etc., but wherever I save the file, it disappears as soon as I restart the raspberry pi.

By: Nishand

Nishand — Sun, 21 May 2017 14:10:19 +0000

Hi,
I have a strange problem, whenever I reboot my raspberry pi, whatever files i have done ( i was trying to write my own code in C++) disappears. I was trying to save my code in Documents Folder, and it stays there as long as the raspberry Pi is powered on. As soon as I shutdown and restart i do not see any files I have saved.

Thanks

By: Mitchell

Mitchell — Wed, 17 May 2017 18:20:03 +0000

Doh! Solved my own problem… It turns out the RPi that I was SSH-ed into had a HAT connected (Witty Pi 2) that also made use of GPIO4 (as and input). When I reconfigured the port as an output it was being pulled low by default, which commanded a shutdown through the Witty Pi.

Live and learn…

By: Mitchell

Mitchell — Fri, 28 Apr 2017 20:58:04 +0000

Still having a great time learning from this book.

I have a question about the Pi related to the push button input circuit of Figure 6.5b: I wired a Pi3 into a project with a switch (instead of a push button) but otherwise configured exactly as shown in the example. It worked fine until I rebooted the Pi – in fact, with the circuit connected and the switch in a state connecting GPIO4 to GND the Pi would not power up. The Pi did boot after I would either disconnect the circuit or toggle the switch to the open state (GPIO4 no longer connected to GND), but I think that pin is now damaged. For example, GPIO4 always shows as exported after booting now, and trying to set “direction” to “out” causes the Pi to shut down (even with nothing connected to the pin).

I am curious whether having pin 7 (GPIO4) connected to GND during boot up is resulting in a short, or at least an over current condition, to ground? What might be the reason for this, and how might one know what pins may be safely wired into a project circuit between power up events?

By: Nishand D'silva

Nishand D'silva — Mon, 17 Apr 2017 02:36:58 +0000

I ‘m having the same issues while running wiringPi programs. The Raspberry Pi locks up each time I try to run any of the programs under wiringPi.

By: Craig Clark

Craig Clark — Sun, 09 Apr 2017 00:21:03 +0000

I have enjoyed you book very much.

I did have an issue with the with chapter 6 wiringPi programs that use pwm (pwm, fadeLED, and servo). When I ran the programs, they would lock up the Raspberry Pi and I was forced to reboot. I could run the demo manually with the gpio program. Finally, I found that using sudo (e.g., sudo ./servo) would run the programs as expected. I don’t know why, but it may be because the Raspbian distribution that I used had the wiringPi installed so I did not do the wiringPi install that you showed in the book. I hope that this might help anyone that ran into the same issue and save them some time.