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2014

The Logic Supply BB100 case has be available for a while (also in black), I purchased one recently while buying other gear, these were my thoughts on it

(pictures were from a cameraphone so apologies for the quality - better images at the Logic Supply website of course).

board_inserted.jpg

 

If you need your BeagleBone Black boxed up, there are worse ways. I thought it was very well made and quite flexible. The cover can be mounted at three heights, to accomodate capes (the gaps can then be used for wires and ribbon cables for example. I will probably fit the Olimex 1400mAH LiPo inside it too as shown here.

 

The case is steel (not aluminium) and in my opinion is extremely accurately cut and shaped. The case has sub-millimeter accuracy. The base and shell are less than a millimeter thick, yet extremely tough because of the choice of material.

 

All connectors are spot-on centered into their holes and the tiny narrow microSD card slot doesn't scrape or touch the card at all.

 

The board is held in place with four screws on permanently fitted metal stand-offs. The finished result is about the size of a pack of playing cards.

interior.jpg

 

The exterior finish is a matt type, slightly roughened surface so not gloss shiny/smooth. I think the finish is great.

Initially I wasn't a fan of the D-Sub connector punch-out (I don't like using this connector for serial connections although it is a standard) but I now think it is a great idea, since it can serve as the I/O for 8 pins or more if a serial port is not desired. On the other side there is a circular punch-out ideal for coax shaped connectors or for a switch for example (approx 6.5mm dia hole measured with a ruler). These punch-outs mean that for many use-cases one may not need to ever drill any holes in the case.

Very narrow slots allow for all LEDs on the board to be visible.

case-closed.jpg

 

Lots of spare screws are supplied in two sizes; the flush ultra-tiny ones shown in the photo earlier, or slightly larger pan-head. By only fitting two screws, the lid can become hinged.

The rear has punch-outs for providing screwed attachment to another surface, or thin vertical slots can be used for fitting to a metal chassis. Really nice engineering everywhere on this case.

Four thin rubber feet are supplied for optional fitting.

The case is not cheap but metal cases usually do cost more, and so this case is fairly good value for money especially if you want a case you can use as part of a demonstration for example.

Postal cost is quite low in Europe for this case shipped from Netherlands, so that helps too.

 

As a summary, the case is very nice and practical, and I think it is worth the cost.

(BBB - Building a DAC part 1 can be found here).

Part 3 implements a complete design in an enclosure for a Sonos-like solution.

Introduction

The BeagleBone Black (BBB) has a digital audio interface and this was explored slightly in an earlier post.

The findings from that prototype were used to construct up a DAC board and it is described here. The aim was to have a relatively simple, easy-to-assemble board designed for portable use (headphone or small speakers) but with at least iPod-level performance. The circuit is described here and the complete schematic is attached to the post. The entire circuit connects to the BBB using 6 pins and needs no separate power supply. This is a recording using just the microphone from the camera - actual audio quality is much better.

 

For a better quality, the audio from the prototype can be heard in this zipped mp3 file. This was directly recorded from the headphone output so that it is more representative of what the user will hear (the original track that was played through the DAC was downloaded from Amazon, for comparison purposes).

dac-board.jpg

 

Detailed Description

This is the functionality on the board:

dac-layout.png

The DAC integrated circuit and headphone amplifier portion were left unchanged from the part 1 prototype although the DAC was replaced with TI’s PCM5102 which is pin-compatible with the earlier PCM5101A. The PCM5102 device is used in commercial DACs such as Meridian’s Explorer.

The remainder design is kept simple too. Three regulators are used to supply power to the DAC (can be reduced to one to save costs, or replace with the lower cost pin-compatible TC1015-3.3):

supply-schematic.png

An optional speaker output was desired, and the selected device was LM4861 which can run from a single low voltage supply and offers over 1W of power. This is enough to provide loud volume for home use (in the video above, the single mono speaker was a couple of meters away and the audio was played at a volume setting of 15 on mplayer). The circuit uses two of these for stereo, although only one needs fitting for mono summed speaker output (the photo above shows only one populated). The LM4861 input is driven from the headphone output, not the line output, to keep line output and headphone outputs as distortion free as possible.

speaker-amplifier.png

The speakers are muted using the LM4861 shutdown pin driven from the headphone socket built-in switch.

shutdown.png

The board was tested with headphones, a small 4 ohm speaker and a larger home speaker. Sound was as expected, and there are no known issues although more testing needs to be done. The board runs cold unless driving a speaker, in which case the LM4861 which is intended to be run without heatsinking in normal temperatures, would perhaps benefit from a tiny heatsink such as this one. The BBB image that I used outputs 16-bit audio at 48ksample/sec (i.e. the sound is as good as a regular CD player), but the DAC will work at higher resolution and sample rates for those with recordings that would benefit from it. The board was tested on an older Angstrom image and a Debian image. There are discussions in the comments section in the earlier post describing current ongoing exercises to get drivers working for different settings.

 

Summary

The described circuit is low cost and provides hopefully nice performance. The complete schematic and parts list is attached.

pbax

BB-VIEW free pins?

Posted by pbax Feb 3, 2014

Maybe I've missed something, but which pins on the BB-VIEW P1 and P2 are not used by the display? I can't tell from the user manual...