CPC webfree extended indefinitely

[fred]

CPC have extended their free delivery offer indefinitely. Applies to all in-stock orders, no minimum order. Details:

[Bob Minchin]

It is good news but I wonder what they will do in the case (which often seems to catch me) that the item appears in stock at the point of order and yet has to be back ordered once they come to pick the order.

Interesting that my RS trade account seems to levy postage on small orders now whereas I used not to get charged any delivery even for the most trivial item.

Maybe I'll use CPC a bt more now and then when the RS reptile wants to know why he's losing business, I can tell him.

[Bob Eager]

That has happened to me, and I've never been charged carriage.

[Andrew Gabriel]

I took my new prototype Raspberry Pi based heating controller along to the Reading Geek Night last night, but it's not ready for use yet. I have two other households in the family who want heating controllers like the ones I did 13 years ago, and Raspberry Pi based seemed like the way to go nowadays, rather than a PC. (It's more powerful than the 120MHz Pentiums I originally used, and even they were overkill.)

[fred]

In article , Andrew Gabriel writes

Are you looking for beta testers ;-)

[Andrew Gabriel]

Urgh... wrong thread, sorry

[Bob Minchin]

Not like you Andrew!

But very interesting to read. I've been wondering about using a raspberry pi as the controller for a solar thermal/solar PV system that I'm building this year.

[Windmill]

I imagine that the cheaper/lower power consumption Model A will be best for most controllers.

Bought a model B last year but have had some problems.

1) The cheap Chinese HDMI to VGA converter (which turned out to be useless for other purposes) does work if I set an appropriate resolution, but I had to fiddle with config.txt on another computer to get to the point where I had a display. 2) The fast 32GB SDHC card from Ebay works in a USB card reader/writer, but fails if inserted into an SD to SDHC adapter. I'm stuck with a slower 2GB SDHC card which does work in the adapter. (Others have reported this sort of problem.) 3) Hot-unplugging USB devices crashes the system and forces a cold restart.

Its a nifty gadget, though, and no doubt things will improve as I gain experience.

[Andrew Gabriel]

I specifically want the wired ethernet connection for remote access, and the power consumption is too low to care about (3W max, IIRC). I won't be running it off batteries.

If you don't want the wired ethernet, you could use a USB WiFi dongle, in which case the Model A would do, but that might end up using similar power.

I used the composite Video connector, but that was because I couldn't find an HDMI lead. Only used it on the first day for setting up though.

I'm using the 4GB Hama SD cards from CPC. They claim up to 95Mb/sec, but I haven't measured, although it seems quite fast.

Try downloading a different or newer distro.

I'm currently using a second generation model B (256Mb RAM which is plenty for what I want). I've bought a 3rd generation (512Mb) because that's what's available now, and will move to it at some point. Some of the GPIO numbers have changed on the connector, so I'll need to do some trivial changes for that. It also has a reset connection which the 2nd generation doesn't have which I could use if I added a watchdog to my hardware, and mounting holes which the 2nd generation doesn't have.

I only used USB on the first day, just to get it up and going with a keyboard and mouse. I now ssh into it, and I can login over the serial port (I put an RS232 driver chip on my controller board), but I may well repurpose that for driving a 2-line LCD display. It was originally going to be used to drive the 1-wire Dallas bus via a 1-wire to RS232 bridge, but I have that working well enough directly from one of the GPIO pins with the kernel bit-banging driver which is included in the current Wheezy distro.

[Windmill]

Odd that current consumption from the USbus isn't given in the specs for most devices. I suppose I should mangle a cable to allow insertion of a meter.

The only composite video device I had was an old B&W football-shaped

5" analogue TV portable, and I could barely read the text on that.

My 32GB SDHC 'card' says it's a 'speed 10' device but only the 2GB 'speed 4' card works in the adapter. And allegedly SD-SDHC adapters contain no logic, just straight-through connections (plus a write protect switch), though I wonder about that.

Yes, I probably need to do that. Downloaded the image in question while waiting for delivery from RS, so it's a bit out of date. I'll see if I can get / need to get the version which uses the hardware floating point instructions instead of software emulation.

I noticed a warning about the risk of shorting the +5V on that connector to the adjacent 3.3V output pin, so I suppose they've made a change to make such errors less likely.

Very useful to have 'reset' when learning!

I've often wondered how the 1-wire thing works. I suppose the protocols must be somewhat similar to RS232, though the latter isn't exactly bidirectional. Presumably 1-wire needs some kind of collision avoidance, like ethernet.

'Plus ca change'. An ancient terminal server sold long, long ago by Digital Equipment was basically a PDP8 bit-banging on multiple lines (at 300 baud max.).

[Bob Eager]

Yup. I used a DECSystem-10 that had more than one of those attached...!

[Andrew Gabriel]

These say speed 10 and SDHC too.

No, just switched the numbers on some of the GPIO pins. If you short any of the several 5V pins to any of the others, you'll probably damage the 3.3V Pi. I actually feed power into the Pi over that connector, not the micro USB power connector.

You can just pull the power cord. The reset is easier if you want to control it with logic, and possibly unattended.

No, it's completely different. You need a 1-wire to RS232 adaptor, which will be a microcontroller. I had been using Peter Anderson's ones

but he's stopped doing the one I used which also had two analogue inputs (although he still does others), so I wrote an emulator for it which runs on the Pi and uses the kernel 1-wire driver, and I added a bit-banging SPI driver to read analogue inputs through an SPI A2D converter (MCP3008).

Mostly not - it's a single master multiple slave architecture. It might do during the bus scan for devices - I haven't looked at that bit of the protocol.

[Mark]

I had to fiddle with config.txt even though our Pi was connected via HDMI to the monitor. For some reason our Pi always wanted to work in composite mode.

We have an early model B we are probably one of the few people who bought a Pi for the purpose it was intended for! In my case it was to teach my youngest to code. For this it could do with more memory and we'll probably get a later model with more memory.

BTW Does anyone know if it's possible to upgrade debian squeeze to wheezy in place or do we need to do a fresh install?

[Windmill]

About 45 years ago, a company in Toronto called Dataline Systems ran an early commercial timesharing service using a KA10.

Interesting times.

[Windmill]

[....................]

Unlikely that I'll ever get round to it - I've always been better at thinking of things I could do than at actually doing them - but if electricity prices keep increasing, it would be useful to have something which monitors inside and outside temperatures and attempts to turn storage heaters off/on during the times the supply is 'on', in order to make the inside temperature less variable. That would need ADCs and control via some kind of heavy relay.

[Bob Eager]

What I was using was a KA-10, and it was 40 years ago. Monitor version

506027.