Raspberry Pi GPIO Control

There is more to it than that.  You have to take in consideration the state of the GPIO pins at first boot.  Even though most of the GPIO pins are set to INPUTS and LOW, they are floating, so I have added a 10k resistor from each GPIO pin to ground to insure a LOW at boot, before I have a chance to set the pins to OUTPUTS and LOW in software, which is done by a script later in the boot process.  As an added precaution, I also have a separate battery with a separate power switch which activates the high current launch line of my circuitry (relay outputs), which I only toggle after the boot process is complete.  I also have various error checking in my C code, including the capture of a hypothetical emergency CTRL-C exit out of my code and setting of all the pins to OUTPUTS and LOW before the program closes.

Very well thought out and designed.

I wouldn't mind getting the info on which pins are low and high at boot.

Perhaps you could PM me some time.

Cheers

Mark

Originally, because things were acting funny on the GPIO pins when I first tried them....some LED's turning on at boot, others not, I thought I may have a defective pi (This was my first time working with GPIO's). Then after measuring the pins and doing a bit of reading on the web, I just picked the pins that were low at boot. Since then, Gordon over at the raspberry pi forums made a couple of nice charts for the REV1 and REV2 boards. The only difference I saw on his REV 1 board chart was that I was seeing a HIGH on GPIO8 at very first boot.

Here are the charts:

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=44&t=35321

As noted, the GPIO pin condition at boot can change after a kernel upgrade, and I imagine a firmware update as well (Thus my layered approach to safety related features in my launcher). However, that said, I have never come across this problem in a years time, so it is very rare.

" I was wondering what you had against it when I saw the extra board, and components."

Actually I never posted a picture of my hookup, but yes, I imagine it is similar to the ones posted.  On the raspi foundation web site front page, they have a post mentioning that they are accepting posts of projects this week from users because Liz is going on vacation, so I requested if they would be interested in my project, but I never heard back, and the week is almost over.  I am not going to go through the trouble of taking pictures, making videos, a long writeup, etc., only to have them throw it in the trash bin.  Thier loss.  If hosting your own web site was a bit cheaper, I would just get my own domain and post everything.....I am still mulling that over.  I kinda better find a job first, and maybe pay off all these extraneous pi electronic parts that turned my pi into an order of magnitude more expensive purchase !

Sorry I jumped from a picture and description into an assumption.

Actually I never posted a picture of my hookup

I can't blame you at all.

I'll have a word to the publisher of the magazine I write the occasional bit for and see if he's interested in a RPi article from overseas, that has some good engineering design.

If hosting your own web site was a bit cheaper

I found a few hosts that were free and with very high storage space available.

We are lucky that the domain price is quite low ($23 per year).

Mark

The cheaper domain registrations here charge only $11 a year.  The popular and reliable web hosting companies typically charge $8 a month (1 year subscription) or $6 a month (3 year subscription) with the domain charge included, for the regular not too crippled hosting plan.  Hostgator and Bluehost seem very popular.  However, they both play games with their prices and features, like when they advertise on the front page $3.95 a month and then you find out you have to sign up for 3 years (sometimes for a crappy plan), or they include web tools that require no HTML coding (Or at least a minimum) which would be nice to start out with, but they cripple them by allowing you to make only 6 web pages unless you pay like an additional $8 a month.  Kinda ridiculous just to post a couple of things, but I am still thinking of going for a year for the most basic plan just to learn a few new things.

Anyway, this is all off topic.  I don't want to turn into one of those couple of top "Top Participants" that constantly turn these threads into multi page unrelated ramblings about all the social woes in the world. That is why I rarely com on this forum and mostly use the raspi foundation forum.

pjc123 wrote:

 

If hosting your own web site was a bit cheaper, I would just get my own domain and post everything

There is no need for a domain name (not even a dynamic one) in order to host your own website.  IP addresses work perfectly well in place of domain names, the only purpose of domain names being as a human memory aid and/or decorative and/or associated with a trademark.  The networking will work perfectly fine without it.

So, if you have a Pi then you have everything you need to host your own website on your existing ISP connection already.  It will have limited bandwidth and throughput, but it's still perfectly adequate for displaying some pictures and project details.  Video links can be embedded from Youtube so they won't consume your bandwidth.

As a bonus, the educational value of running your own service is much higher than using a commercial website, and you don't need to pay website fees, and you avoid the recurring pain of domain expiry/renewal.  Of course if you can afford a domain name or can use dynamic DNS then it'll be prettier, but if cash is really short then it's entirely optional.

Today I stumbled upon a video instructing how to connect 8 channel relay + Raspberry Pi.

Here it is:

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Manny

Just be aware that some work fine, others don't work so well with only 3v3.

There has been a suggestion on Terry's site about dropping the resistor value in series with each optocoupler.

We had a discussion about it here earlier.

Mark