Dirty Circuits Done Dirt Cheap

Often design and research is and expensive business, especially when dealing with technology that your are unfamiliar with. A big proportion of this is PCB manufacture and I have spend a few years looking for a low cost reliable method for PCB production.

The most cost effective method is to have the boards produced overseas but then you won't be sure of the quality of the boards until they return. This is where Dirty PCB step in.

Dirty has been setup by the guys at Dangerous Prototypes as a reliable access to PCB fabs overseas.











I discovered Dirty PCB while looking at another PCB manufacturers reviews and recommendation on a forum post.

So went over to there website and I was almost knocked of my feet at how cheap 2 layer PCBs were.

If you can keep your design under 5cm x 5cm and don't mind if you end up with anywhere between 8 - 12 PCBs then it is only $14 (9GBP) that could be less than 0.10GBP   1GBP per PCB. WOW! There is also a selection of colours for the solder masks at no extra cost.

For me that is great for me as most of my designs are under this size as 50x50mm is quite equate for a breakout board but for $11 more you can have up to 10cm x 10cm (100x100mm That's huge). 

There are a few things that you need to accept to get this price level the boards can only be 2 layers and the pad finish will be HASL (Hot Air Solder Leveling) there is an option for ENIG (Electro-less Nickel Immersion Gold) but it is $15 more. Also there free postage option is quite slow so its worth paying $19 more to get DHL airmail, I realise this is more that the PCBs cost but otherwise it could be a up to 8 weeks delivery. 

Next thing to have a look at is there capabilities, this is all listed in the FAQ.

Capabilities

ITEM	CAPABILITY
Material	FR-4 0.6mm-2.0mm 1oz copper ('standard' PCB material is 1.6mm thick, but we default to 1.2mm)
Layer number	2L
Maximum size	100*100mm (10*10cm)
Shape	Almost anything! We'll send it and see if they accept it!
Min internal slot	32mil (0.8mm)
Min core thickness	4mil 0.08mm
Min core thickness	16-96mil(inner) 16-118mil(out)
Min w/s	5/5mil(I/L)
Min w/s	5/5mil(O/L)
Min silkscreen line	0.15mm
Min BGA size	Oblong:10*13.5mil/circle:12mil
Min SMD width	8mil
Min solder dam	3mil(green)/3.5mil(black)
Min dielectric thickness	2.5mil
Min diameter of finished hole	12mil
Tolerance of drill position	+/- 2mil
Tolerance of finished hole size	PTH +/- 3mil
Tolerance of finished hole size	NPTH: +/- 2mil
PTH hole copper thickness	0.6~1.4mil
Max A.R of PTH	8:1
Surface copper thickness	1oz
Routing dimension tolerance	(Z0) Impedance control 4mil
V-cut	Now refused! 80*80mm(min) 380*300(max)
(Z0) Impedance control	+/- 15%
Ionic contamination	< 6.4ugNaCl/inch2
Surface treating	(No PB) hot air levelling/AuSn/AgCN/Electrogilding/Ni/OSP*/G.F
*OSP	Organic solder-ability Preservatives

This is much the same as most board houses standard service I'm mainly looking at the trace thickness and clearance which is 4 thou (thousandths of an inch, this is a bit of a legacy thing with board houses) and a clearance of 5 thou.

There is some helpful things further down the page, Dirty PCB supply a design rules check file for Eagle this file is use in you design rules check to make sure your PCB design is manufacturable. They also supply a cam processing file to help export your design manufacture file. But if you use Eagle like I do you can just send in your .brd design file and Dirty PCB will do all the exporting for you. This is great as I don't have to worry about getting the export wrong or sending the wrong layer files.  

So that's it time to give them a spin. Note: Dirty PCB only accept PayPal payments best to make sure you PayPal details are upto date.

On thing I noticed after putting in my order is that the level of communication is amazing are reassuring, and you can also check the status of you order in the websites status page.  

One Week Later (seriously that is really really fast!)

Such Box! Much Cute! 

There is no mistaking this box the end stamp is very cool.

And then you even get a sticker, I like stickers :)

The PCBs where well wrapped but a little loose in the bag the could rub against each other possibly scratch the finish but this didn't happen in my case. 

I always get excited to see one of my own designs as PCB please don't get too excited this is not a product its just a demo board to try out a BLE chip that I might use in a product ;)

The finish is great the Silkscreen is legible and the resist is nice and even. lets have a look under the microscope.

The quality is excellent and precise the soldermask is tight to the pads with none of the ground fill exposed. The thing that really knock me off my feet is they have also managed to apply the mash between the the pads on the main package, these gaps are less than 0.2mm in width that is brilliant.

  

 And for the free sticker.

Got the perfect place for that.

So what do I think of Dirty PCB here is my round up:

• Easy of use: Straight forward and quite fun the site feels as though it doesn't take itself to seriously and approachable. Though more payment options would be a nice addition.
• Communication: Reassuringly comprehensive without feeling like I'm being spammed.
• Lead Time: Quick! 
• Packaging: Exciting!
• Finish and Quality: Astounding good.

I can only award Dirty PCBs up to 5 sparks but in may opinion they deserve 6. Very pleased with the service.

  

  

Pi Supply Gert VGA666 Software Setup and Test

This is how to Set up the Gert VGA666 for Pi Supply I have a previous post on assembling the components if you haven't already done so please check it out here.

Installing and Configuring software 

Be aware that you are changing the where the Pi is going to output it video if you have the option I would recommend setting up over an SSH connection.

Firstly you'll need to download the required software to run the Gert VGA 666. Make sure your Pi has an internet connection.

git clone https://github.com/fenlogic/vga66.git

Then you will need to copy the driver file into /boot/ and rename it.

cd vga666/setup/

sudo cp dt-blob-dpi.bin /boot/

sudo mv /boot/dt-blob-dpi.bin /boot/dt-blob.bin

Now the final step is to add it to your raspberry pi configuration.

So to open the configuration file.

sudo nano /boot/config.txt

The you'll need to add.

 enable_dpi_lcd=1
display_default_lcd=1

This will enable the VGA output. Then you can set the output resolutions by adding

dpi_group=2
dpi_mode=82

 For 1080p @60Hz or.

dpi_group=2
dpi_mode=86

 For 1366 x 768 @60Hz

These are the two screen modes I have tried myself please now the resolution values are the same as setting the resolution for the HDMI output, a full list can be found here.

Problems you may run into 

The first time that I tried this the VGA work for about 10 seconds of boot time the the text turned yellow and then vanished dropping my screen into power saving.

I was using a Rasbian image that had some of the GPIO setup for various tasks so it was 'grabbing' some of the GPIO for other tasks this was fixed with a fresh burn of Raspbian.

In conclusion 

This is great add-on to the Raspberry Pi and the documentation makes for interesting reading as it goes into an explanation of how it generates and analogue signal from the GPIO header, and makes for great learning and soldering practice.

This is in no way the perfect solution for VGA output on the Raspberry as it will have the occasional slight shimmer on the display and it uses huge chuck of you GPIO to drive it. So if your you are looking for a VGA output from your Raspberry Pi I'd recommend a good HDMI to VGA adapter.

So I award this 3 of 5 Sparks it was fun to assemble the documentation could be a little clearer but as a learning exercise it's fantastic.

$4 Dollar ARM development platform

Cypress Semiconductor a US based chip manufacture are pushing down the price point on Development boards. They have released two development boards based on there PSoC 4 series Microcontrollers and priced the boards at $4.

The Unimaginatively Named PSoC 4100 and 4200 Prototyping Kit are powered the PSoC 4 ARM Cortex-M0+ based with a nice stack of peripherals including UART, SPI, I2C PWM and on the 4200 kit and an upto 12 bit 1Msps SAR ADC this is not to mention 36 GPIO pins.

The added bonuses of this board is that it comes with a built in programmer that can be broken away to embed the board into your design while retaining the programmer so it it possible to flash already embedded MCU's

These Development boards are a very cost effective way of getting it ARMv6 programming and 32-bit architecture. The development suite is a little tricky to get up and running but it does have a few nice features like the ability to visually configure the MCU's IO ports and peripherals with the added bonus of being able to swap some peripheral pins around for your design. 

All in all I give this 3 Sparks cheap lead-in, but setting up could be easier.