Multifunction instrument based on BeagleBone Black

Hi shabaz,

Yes I do have some ideas for its use, my 4ch scope died a while back, thick black smoke and all.   I have been tinkering with high speed ADCs and FPGAs running currently at 60Mhz and transferring data to my PC over USB.  Then along came BBB and it's PRUs  so my thinking is more along the lines of a multi function device, basic scope, logic analyser, frequency counter..... 

Anyway back to the LCD4 cape some good points:

• Full circuit diagrams available here
• LCD module NewHaven NHD‐4.3‐480272MF‐ATXI#‐T‐1 info here app note here
• Resistive touch screen so can use a nice thin stylus instead of thick stubby fingers.
• The two LEDs on the board are GREEN

The cape works as the x-windows desktop with the standard distribution but as it resolution is only 480 x 272 a lot of the X applications are written for higher resolutions so their windows and menus end up half off screen with no way to get at everything.  I have tried it with the latest 2013-05-27 Angstrom image which has a few issues ( the kernel is still in a state of flux so these problems are being worked on) for this cape apparently the pull-up/pull-down resister configurations for user buttons are not being set correctly so they are triggering multiple hits.  There are 4 holes which match up to the BBB mounting holes but you can't use them without first removing the LCD panel which is attached to the PCB with sticky pads. There are 4 more mounting holes for the cape PCB that are accessible.

That's as far as I have been able to get for now as we have been invaded with grandchildren and I have nowhere to hide   I will dig a lot deeper when I get the chance.

Sources of inspiration.

Whilst researching what is available I recently came across this from Digilent - Analog Discovery, Priced at $99 for US Students, $159 Academic and $199 for the rest of us (£136.09 Farnell UK) A real problem for me though is it's not open source and is tied to a windows PC. I think this type of product, designed for the education market, should be open source but that's another story. I have recently spent a lot of money on BBB bits and pieces so whilst I would love to play with one and see if I could interface to it a BBB and produce a linux / BBB equivalent to their software, I can't justify the expenditure at the moment. It would still be great if I could get one at the student price, better still if Digilent gave me one along with the design info   Then again it would be great if I won the lottery. Well enough of the dreams back to the black...

I got to thinking about designing something with similar functions but not tied to windows or PC.  I looked at the R-Pi which has great graphics capability but little I/O and I have had a number of issues using the USB at high speeds.   Then along came BBB and it was like the proverbial light bulb switching on. All the I/O pins and two PRUs and more than adequate graphics and and and....

As Morgaine mentions above the OBLS and other "open source" products offer a solution and provide already working designs. I believe this to be a logical first step.

Thoughts then are to use this wealth of usefulness and cherry pick the best bits to a fully integrated product onto a cape or two.

Ok a tiny little bit of top-down design:

1. Low cost portable multifunctional instrument capable of but not limited to being a Logic analyser, Oscilloscope, waveform generator, frequency spectrum analyser ...  A design that has both digital and analogue functions.

1.1 Overall system control User interface and display
1.1.1 Beaglebone Black with either LCD + Touch screen or (not so portable) HDMI monitor, keyboard and mouse.

1.2 Digital functions
1.2.1 FPGA Cape with I/O buffering and protection linked to BBB PRUs for real time control and data transfer

1.3 Analogue functions
1.3.1 ADC + DAC Cape linked to FPGA cape for high speed capture and to PRUs for real time control

At this moment in time I am still getting to grips the the BBB and it's evolving 3.8 kernel and the various O/Ss that are available. Angstrom is ok, Ubuntu and Debian are fine but I quite like Arch Linux.  Of course the software for the "instrument" must not be dependant on any particular one though.

It's getting late so I will leave it  there for now.

Brian

Many thanks, Drew.

This is a great split, very helpful indeed!  Even if we don't pursue a full-blown cape, many measurement-related ideas and/or links to related material can find a good home here.

Morgaine.

Brian Welsby wrote:

 

1.1 Overall system control User interface and display
1.1.1 Beaglebone Black with either LCD + Touch screen or (not so portable) HDMI monitor, keyboard and mouse.

Worthy of note is that while the Pi's 1920x1200 resolution gives it a clear edge for media centre use, the BBB's 1280x1024 max is more than ample for an instrument display.  Indeed it would probably be overkill for most instruments.  On the display side, even without considering the BBB's mass of GPIOs and the PRUs which put it into another league entirely, this board seems very well matched to requirements.

1.3 Analogue functions
1.3.1 ADC + DAC Cape linked to FPGA cape for high speed capture and to PRUs for real time control

 

At this moment in time I am still getting to grips the the BBB and it's evolving 3.8 kernel and the various O/Ss that are available. Angstrom is ok, Ubuntu and Debian are fine but I quite like Arch Linux.  Of course the software for the "instrument" must not be dependant on any particular one though.

I've mostly shied away from the analogue side of EE throughout my career, so application notes and reference designs are my friend.   I expect that the big players in analogue all have highly integrated devices for instrumentation front ends these days, with application notes to match.  With a bit of luck, creating reasonable instrument circuitry might be mostly a matter of component integration and careful layout+shielding, rather than original analogue design.

Regarding operating systems, I agree with you there.  Whatever our personal preferences, the distros with the largest communities and the best support are likely to provide the quickest path to actually using an instrument, rather than spending days messing with the operating system.  Debian and Ubuntu have a clear lead there, followed by derivatives of these that use compatible ARM binaries and the same package management..

Morgaine.

Morgaine Dinova wrote:

 

Worthy of note is that while the Pi's 1920x1200 resolution gives it a clear edge for media centre use, the BBB's 1280x1024 max

It turns out that the BBB isn't exactly limited to 1280x1024 as such. The limitation is down to the 125MHz pixel clock, or 85MHz if you want audio.

This is a limitation of the am3359 it seems. The hdmi framer is capable of much more.

Still, it seems that you can do 1920x1080x30 with audio, and the full 1920x1080x60 without audio - at least in theory. There's more work on the driver needed to enable it though.

https://groups.google.com/forum/?fromgroups#!topic/beagleboard/4vge3Zs8dYE

Brian Welsby wrote:

 

Of course the software for the "instrument" must not be dependant on any particular one though.

I think the OBLS is a reasonably good example here, the preferred app to use with it is written in java and just needs to be able to open a connection to the board.

So the OS needs to be able to provide the environment needed to run the java app and, in the case of the OBLS something like libusb to talk to the hardware.

Now if you want direct connection rather than usb, perhaps spi-dev, or write a kernel driver to provide a /dev entry to talk to your hardware. Either way you're relatively independant of the OS, any hard stuff could be done in the kernel.

I did get 1920x1080p/24 on my Sony TV with one of the latest kernel builds so yes work is in progress.

Looking at the framer data sheet (sorry can't remember where I found it now) it may also be possible to support 3D @ 1920x720 side by side but that is definitely for future experimentation once the kernel is stable.

I have got all the openjdk installed and working and I am in the process of checking it out with the OBLS code. I think a user interface re-write is needed for low resolution LCD usability though.

Brian Welsby wrote:

 

Angstrom is ok, Ubuntu and Debian are fine but I quite like Arch Linux. 

Angstrom seems to be better optimised for the BBB, but has it's share of difficulties.

Ubuntu/Debian are nice from the point of view of getting a generic, familiar, and supported distro. I always feel they're a bit heavy for the likes of the Pi or BBB though, but that's a common theme for any of the traditionally x86 desktop oriented distros

I did like Arch. Up until they did the whole /lib -> /usr/lib thing and followed various others off the systemd cliff in a fairly decent lemmings impression. (My olinuxino arch install became basically useless after that as it became effectively impossible to upgrade past a point and therefore couldn't use many of the newer arch packages)

While there are various distros that fit a range of needs, I still feel there's a lack of a good option that targets an embedded device without bringing lots of baggage along for the ride.

Brian Welsby wrote:

 

Looking at the framer data sheet (sorry can't remember where I found it now)

Interesting, I never could find one. NXP's website only seemed to have some marketing blurb saying it dould do various things with no real details.