Workshopping £1.40 Arduino-Compatible (£3.05 including USB!)

Actually, I got the diode backwards - should be anode to Reset, Cathode to Power. I'll fix my earlier post.
Want any spikes on the Reset line dissipated to the power line.
Diode like 1N4148 will do.

The 10uF Electrolytic (usually aluminum electrolytic) helps with any big current ripples, while the 100nF help with higher frequency stuff and short term current demands.

You don't have any extras to remove. The last diode & cap get you up to the minimum for an Arduino.

CrossRoads:
Actually, I got the diode backwards - should be anode to Reset, Cathode to Power. I'll fix my earlier post.

That makes loads more sense, thankyou. Based on the original description I figured it could only be doing something useful via reverse breakdown.

CrossRoads:
Want any spikes on the Reset line dissipated to the power line.
Diode like 1N4148 will do.

Great, I have all the relevant info to order stuff now.

CrossRoads:
The 10uF Electrolytic (usually aluminum electrolytic) helps with any big current ripples, while the 100nF help with higher frequency stuff and short term current demands.

OK, so I still need both.

Within the workshop I think I'll introduce a functioning (programmable) circuit without all the extra components, (just flashing a LED), then later (and before transfer to stripboard or working with servos etc) introduce all the protective components (caps and diodes) with an explanation of various forms of noise spikes, transient load and ESD which are likely when deploying in the field.

Hopefully then the extra 5 components won't freak people out too much when introduced under the heading of 'protection'. My aim is to have as little 'black magic' in the design as possible - the one perceived weakness of the nice shiny blue boards is that they are beyond novices to interpret and understand, compared to something you've wired yourself :slight_smile:

CrossRoads:
You don't have any extras to remove. The last diode & cap get you up to the minimum for an Arduino.

Hurrah. Time to crack open a celebratory beverage (6pm here in UK).

An update on the Laptop Shrimping project. We now have a URL at http://shrimping.it and Twitter @ShrimpingIt

The #Shrimp design is fairly stable now thanks to many contributions from people who know stuff.

I've personally distributed about 30 kits of parts. Some are taken with a breadboard, some with USB-UART adaptor, and some taken by hobbyists to put onto stripboard at home. However, the most exciting direction is feeding in to the National Curriculum and STEM subjects here in the UK.

Thanks to @teknoteacher for making me realise something like the #Shrimp was needed at Hackademy "Inside the Machine" Hackademy ‘Inside The Machine’- Oct 26th 2011 – teachcomputing.wordpress.com Thanks to @oomlout for early discussions and support and thanks to @tshannon for hosting and supporting Shrimp makers at Howduino. Thanks to @jonachamberlain @patlink72 @iMartyn and his Mum for testing out the first boards and working with me to think of decent expansion kits. Thanks to Mike Cook for all his experimentation with a clone of the MB Games 'Simon'. Thanks to @monsonite and @simonmonk2 for suggestions. Thanks to many many others including those in this thread. Sorry if you've helped I didn't credit you by name but I've had a huge amount of fun and engagement with loads of people.

There's a lot of excitement about being able to actually solder together your own Arduino-compatible. Thanks to Fignition, and @ManchesterBudo for helping me realise how important this is to people - it's now become central to the project.

Essentially, this is developing into a classroom pack which teachers should be able to progressively introduce to pupils, with a single lesson to build the circuit and program it on breadboard, another lesson to prototype established project designs from 'expander' kits (which include some extra sensors and actuators for a specific project), and a final lesson to solder onto stripboard and test on battery. At any point, it is feasible for individuals to take a direction towards their own personal project/invention/game/alarm/joke/toy what have you. We're just offering a kind of template for leading people through this.

All along the way, you're working directly with incredibly cheap components and using the same 'mental model' from the moment you start building your Arduino-compatible, right the way through to prototyping your own project circuitry - one advantage of not using the blue board, at least for education purposes. There's a huge crossover with Design and Technology subjects, and it's loads of fun designing, choosing and packaging glossy buttons, displays etc. even for those who don't want to change the circuit or the program.

Here in Morecambe the rough plan is to make the components for a Shrimp available for £3 at workshops, with a returnable deposit of £2 for the USB-UART adaptor (which you may not need when you've finished building your project), and a returnable deposit of £3 for the breadboard (which you can give up when you've finished prototyping and you've transferred to stripboard, or maybe you found a cheaper breadboard :slight_smile:

Hopefully people will get involved enough that they want to keep both the CP2102 and the Breadboard for further projects, and we can keep giving them packs of £3 components for each new experiment they undertake, with the aim that they actually deploy their experiments, powered by battery or a USB power source (without UART), and don't deconstruct them again as people like me tend to do with Arduino because of owning a limited number of boards.

Anyway, it's been a bit whirlwind. The moment I get any parts, people seem to take them away, so I've bought another load of 100 lots from mouser/tayda/shcfstore (the cheapest places I've found to get the bits so far). The CP2102s could take a while to arrive, unfortunately, but I'll have all the other parts within a week.

We can help you get the parts at a reasonable rate, and with rapid shipping from UK but we are not claiming any ownership of the design, though it's nice to get credit and pingbacks.

If you're interested in following along, getting a kit of parts or contributing to the project, then get in touch @ShrimpingIt http://shrimping.it

Latest developments now mean we can make the components for an Arduino-compatible circuit available to Morecambe hackers for around £1.40 in component costs, or £3.05 including the CP2102 USB to UART adapter.

This is a fairly major development, putting a binary-compatible #Shrimp about one tenth of the cost of a retail Arduino!

I'll change the thread title to reflect this. To find out more, visit Bill of Materials for the Shrimp circuit

That`s incredibly cheap!

You program the AtMega chips yourself?

Nice to see some arduino action from across the Bay! :slight_smile:

I'd like to hear from you if you've actually got the CP2102 module working programming the Arduino, i've got a very similar setup on breadboard at the moment and having nothing but trouble programming it!!

:frowning:

Regards

Matt

I use the one shown here, I`ve modified it for auto-reset.

I have that exact same one, mine set-up in very similar way, just put some headers instead of cutting and rerouting the DTR. Still doesnt work for me thou! :frowning:

Just like Lakes says, you need to use the pin labelled DTR on the CP2102 to wire to the reset pin (pin 1 on the ATMEGA328P). All the CP2102s I've been passing on to people are exactly the same as Lakes, and have a right-angled male pin header manually soldered in place there. This really has to be detailed better on our website, sorry.

There's a picture of a minimal Shrimp on a breadboard which uses a modded CP2102 and matches Lakes' schematic exactly (apart from the LED) in the Shrimping Safari article at http://blog.safaribooksonline.com/2012/07/03/time-traveling-with-old-laptops-and-arduino-compatibles/ It looks like this...

However, there's a bunch of commentary in this forum thread which suggests some additional protective components which should be added for stability if you're trying to make a general purpose Arduino-compatible on a breadboard. The argument is that the components are so cheap that they're not worth trying to eliminate them, which we'd have to agree with, given our bill of materials at Bill of Materials for the Shrimp circuit

We've tried to incorporate all of these insights in the latest layout which looks like this...

Alternatively, if you haven't access to a soldering iron, get the timing really good on hitting the reset button (which you need to wire with a pull-up resistor as per the http://shrimping.it schematic). Hit the reset button just after Compiling and just before Uploading. You have about a microsecond :slight_smile: Seriously, though, it's not that tight. I can generally get it every time.

If anyone wants to send me a (really clear) picture of their busted breadboard layout I can try to figure out what's wrong. Equally if there's anything else I can help with by way of parts or what have you, then get in touch especially if you're in the North of England. There's bound to be some way I can swap some bits with you for sanity checking whether things are roasted.

Contact me via this forum or http://shrimping.it If you're happy for me to share your pictures it would be good to have a resource of examples which need various fixes.

I'm relying on Bill Westfield's totally amazing Optiloader for flashing chips from Mouser. It does have a weird behaviour after I've flashed them. If I try to reflash them it seems to report they're busted, but they're actually fully functional. I think it's just a counterintuitive error message. I should file that on the Optiloader github when I get a chance.

I did have a DOA CP2102 but only one out of the 50 or so which I've bought, and I don't know what people did with it when workshopping, so they could have really zapped it somehow. Put it this way, I'm not going to try and get my money back :slight_smile:

bromatt:
I have that exact same one, mine set-up in very similar way, just put some headers instead of cutting and rerouting the DTR. Still doesnt work for me thou! :frowning:

Have you tried doing a Loopback test with it?
Also its easy to get the Tx and Rx wires swapped around when using it with a breadboard... :wink:

@bromatt when you say "it doesn't work for me" what exactly are you experiencing.

If you can't reprogram it even manually with a (well-timed) reset button push then I'd stop investigating the DTR pin and look at the rest of the circuit, especially the TX vs RX as Lakes points out.

That one (inverted serial pins) foxed me with an entire workshop full of people when I'd done the diagram they were all working to the wrong way round [facepalm].

Does anyone have a view on the stability implications of placing the large electrolytic cap on the opposite side of the circuit. I'm guessing it's only going to respond over a relatively long timescale anyway compared to the smaller caps (which are there for rapid response).

Having it on the other side would be really useful given the left hand side is really packed when using just the 5 rails of a breadboard/stripboard...

However, it's not worth doing if it defeats the object of the cap altogether.

cefn:
@bromatt when you say "it doesn't work for me" what exactly are you experiencing.

If you can't reprogram it even manually with a (well-timed) reset button push then I'd stop investigating the DTR pin and look at the rest of the circuit, especially the TX vs RX as Lakes points out.

That one (inverted serial pins) foxed me with an entire workshop full of people when I'd done the diagram they were all working to the wrong way round [facepalm].

Hi,

Done the loopback test, tried swapping the TX/RX still have the same problem! :frowning:

My problems are detailed in another post on here... http://arduino.cc/forum/index.php/topic,121571.0.html along with a photo of the board...

Regards

Matt

Just had a thought! Could it be the bootloaded chip? I mean I was under the assumption that the supporting hardware on the Uno was nothing more than a USB/Serial adaptor anyways so there shouldn't be any difference should there? And what is the routine to put the 328P into programming mode? is it just a matter of timing on the reset? or is there something more complex?

Matt

If you mean doing a manual reset, yes you have press that button at just the right time, which is a pain..

Otherwise, you need to look at the AtMega side now, check your wiring, is that crystal really oscillating?

The only way to be sure is to Nuke it from Space... I mean use a known working chip... :smiley:

I tried using a uplink and piloting the drop ship remotely....actually..... 8)

Crystal is ok - I had the blink test program running on the board (i programmed the chip in my Uno just to make sure).
Chip is ok - I programmed it in my Uno just to make sure. (is there an echo in here???).

Matt

@bromatt we should probably continue discussion of your layout/wiring/config issue on the other thread http://arduino.cc/forum/index.php/topic,121571.0.html but if you're still stuck after all the helpful advice, after I've finished my deadlines from 11th September, I can post you a full tested set of parts, then you can post your duff layout back on the breadboard for me to figure out what's wrong.

That way I gain a breadboard, (really useful for workshopping here in Morecambe), and maybe a 328P-PU (I'm working with the cheaper 328-PUs)! At worst, I'll have swapped a good CP2102 for a fried one, but that's fine by me. If you're heading for Preston Raspberry Jam or OSHCamp we could cross paths there, or you could join us at a future http://shrimping.it workshop in Morecambe.

Let me know if that's interesting to you.

Thanks for the offer, i may just do exactly that if I continue to have these problems, discussion moved to my other thread!

Matt