Beaglebone cape in the works.

[yyrkoon 250]

So we've been working on a project that required that beaglebone to be rock solid in a remote location. In order to do this we had to add a few things . . .

 

1) A working watchdog circuit. As the on die watchdog for the am335x either does not work properly, or does not function after the board loses power

2) A functional RTC. As the on die RTC does not keep time when the beaglebone loses power.

3) Additional battery functionality circuitry. As the PMIC on the beaglebone does not take several things into account. Such as disconnecting the battery when the 5v input goes missing. But this can not be done arbitrarily. It needs to be done in a clean fashion. To keep form corrupting the mmc media the board boots from.

 

All or most of the above was a design / cost decision made by the person who designed the beaglebone. As in, 'fine you want that feature ? well it'll raise the cost of the board' type situation. So I can certainly understand where Gerald was coming from. I rather like the idea of buying a $45 BBG with what it does have ( as it sits ).

 

Anyway, we're designing a board around the above mentioned items we added into the custom cape we designed. However, we'd like to hear from others what else would be usefull to add to such a cape that would make the cape useful for many people while keeping the cost down( affordable ) for the hobbyist. We've tossed around a few ideas such as adding x amount of grove connectors. Or simply a 'port multiplier' type 'port' for an I2C bus, where one would add x amount of I2C devices / sensors.

 

What would *you* like to see in such a cape ?

[bluehash 1,581]

When you say remote, how remote? Will the cape have a cell modem?

[yyrkoon 250]

When you say remote, how remote? Will the cape have a cell modem?

When I say remote, I mean as remote as the user wants. This design is meant to automatically reset a hung beaglebone, disconnect the battery 30 seconds after 5v input goes missing. Giving the beagleobne enough time to shutdown via the service acpid. Then keep time via a working RTC. A cell modem would add too much cost to our cape, but nothing stopping someone from adding their own.

 

As I mention above. The idea is to add as much as possible, but remain generic enough that everyone could have a use for the cape. While keeping costs low as possible too. It gets old buying a cape that costs 150% or more the cost of a beaglebone. 

 

@@bluehash why do you ask ? DO you need such a cape designed ?

[yyrkoon 250]

One idea we were kicking around with today. Was *maybe* a "regulator" addition. That is imagine a remote site with a 12v solar panel, and a 12v deep cycle for providing long term power. A design could include a 12v, or even a wide DC input voltage regulator to 5v power for the beaglebone. Kind of like a UPS, as our cape already uses a 3.7v LiPO. But I could see a potentially large need for this design in the scientific crowd ( extreme remote site data acquisition ) We could even design a solar charge controller into such a cape . . .

[yyrkoon 250]

@@bluehash here ya go: http://nimbelink.com/skywire-beaglebone-black-modem/

 

But like I said in my last post. The cost of that cape is ridiculous in my mind. Cost is twice the cost of a beeaglobone( $110US from Digikey ). Also I've talked with someone who has used one. It uses some sort of hokey UART USB gadget interface. But I guess if you *REALLY* need one . . .

[spirilis 1,265]

I never bothered to follow up with my idea below but I do think a switching regulator for 12V (maybe modifiable to work up to 60Vin for flexibility with different offgrid DC power systems) is a good idea.

 

I designed and built one copy of a 12VDC PFET power MOSFET cape which had an off-the-shelf 12V (7-36Vin) to 5V out switcher onboard. It worked great. I highly recommend including one for your design.

 

The idea behind my cape is 12V could be switched on/off to up to four outputs for remotely controlling power for various sub-5A sources e.g. a low flow pump. The beaglebone is powered by the same 12V source obviously.

[yyrkoon 250]

Will still have several proto capes laying around but interest seems rather limited on those . . .

[yyrkoon 250]

I never bothered to follow up with my idea below but I do think a switching regulator for 12V (maybe modifiable to work up to 60Vin for flexibility with different offgrid DC power systems) is a good idea.

 

I designed and built one copy of a 12VDC PFET power MOSFET cape which had an off-the-shelf 12V (7-36Vin) to 5V out switcher onboard. It worked great. I highly recommend including one for your design.

 

The idea behind my cape is 12V could be switched on/off to up to four outputs for remotely controlling power for various sub-5A sources e.g. a low flow pump. The beaglebone is powered by the same 12V source obviously.

 

Not really interested in switching 12v so much, just regulating down to a more 'manageable' voltage. So having a buck converter would definitely be needed. buck/boost however . . . from what I've seen seem to have a narrower input range. I'll have to give a good looksee to see what all is out there right now.

[bluehash 1,581]

@@bluehash here ya go: http://nimbelink.com/skywire-beaglebone-black-modem/

 

But like I said in my last post. The cost of that cape is ridiculous in my mind. Cost is twice the cost of a beeaglobone( $110US from Digikey ). Also I've talked with someone who has used one. It uses some sort of hokey UART USB gadget interface. But I guess if you *REALLY* need one . . .

We use the Nimbelink for some of our projects and conferences. We have the Ethernet to Cellular E2CLink.

Cost is crazy and it is not in any production equipment.

 

I asked because you mentioned remote. BT/Wi-Fi/Sub 1Ghz are all nearfield.

I get where you are going though. If the BBB has trouble doing all the stuff mentioned in the first post, another way to get around that is to use a micro connected in serial managing the BBB./PMIC/Battery/RTC. The downside is more code development, another processor family, board space+BOM count.

 

Maybe an application note using any of the widely used Telit GSM modules will be a good starter/reference.

[yyrkoon 250]

I get where you are going though. If the BBB has trouble doing all the stuff mentioned in the first post, another way to get around that is to use a micro connected in serial managing the BBB./PMIC/Battery/RTC. The downside is more code development, another processor family, board space+BOM count.

This is pretty much what we're doing already, except the solution is not all in one chip. Connectivity is all via I2C though. Which I still have to work out in code for the msp430, For the board we just did a production run on, we did not use I2C. Just a single GPIO, and a toggle count to enable the watchdog feature. It's actually pretty awesome for me to watch it working, as the very first time I ran it it caught, and dealt with a failed boot on the beaglebone. Which is of course why I came up with this idea to begin with. The rest of the features I added after observing the beaglebone in action for 3 and a half years, while noticing 'minor' flaws. Minor as in they are minor flaws, until you actually need the board to go into a production system. Then they become serious flaws.

 

The real cool thing is that none of this requires anything special on the beaglebone to function correctly. Software wise. You can even run all of this without any special drivers on the beaglebone side. It's a simple matter of connecting these devices to an I2C bus, and using i2c-tools utilities if the user so wishes. However, Linux also has a 'built-in' driver for the ds3232 RTC, which is fairly handy, and really simple to use too.

 

Anyway, it is my hope to keep costs below $25 per board if possible. The more features added however . . .will increase the cost, of course. Which is why I think adding power switching circuitry is not necessarily a good idea. Regulating a wide range input, maybe. However, with that said, perhaps something like an 'add-on' could work ? I'm kind of envisioning something like a grove connector, that would allow inexpensive add-ons via an i2c bus( for control ).

 

EDIT:

 

@@bluehash I was talkign with a friend of mine about cell phone dongles, and he claims that there are USB dongles that cost less than $20. I have not looked into this myself, but if they truly do exist in this price range. It then becomes a simple matter of "bullet proofing" the software ? I'll look into it.

[spirilis 1,265]

This is pretty much what we're doing already, except the solution is not all in one chip. Connectivity is all via I2C though. Which I still have to work out in code for the msp430, For the board we just did a production run on, we did not use I2C. Just a single GPIO, and a toggle count to enable the watchdog feature. It's actually pretty awesome for me to watch it working, as the very first time I ran it it caught, and dealt with a failed boot on the beaglebone. Which is of course why I came up with this idea to begin with. The rest of the features I added after observing the beaglebone in action for 3 and a half years, while noticing 'minor' flaws. Minor as in they are minor flaws, until you actually need the board to go into a production system. Then they become serious flaws.

 

The real cool thing is that none of this requires anything special on the beaglebone to function correctly. Software wise. You can even run all of this without any special drivers on the beaglebone side. It's a simple matter of connecting these devices to an I2C bus, and using i2c-tools utilities if the user so wishes. However, Linux also has a 'built-in' driver for the ds3232 RTC, which is fairly handy, and really simple to use too.

 

Anyway, it is my hope to keep costs below $25 per board if possible. The more features added however . . .will increase the cost, of course. Which is why I think adding power switching circuitry is not necessarily a good idea. Regulating a wide range input, maybe. However, with that said, perhaps something like an 'add-on' could work ? I'm kind of envisioning something like a grove connector, that would allow inexpensive add-ons via an i2c bus( for control ).

 

EDIT:

 

@@bluehash I was talkign with a friend of mine about cell phone dongles, and he claims that there are USB dongles that cost less than $20. I have not looked into this myself, but if they truly do exist in this price range. It then becomes a simple matter of "bullet proofing" the software ? I'll look into it.

I think having specific support on the board for "daughterboards" providing advanced power support is a great idea.  A pinout giving access to 5V, GND, maybe 3.3V, and I2C along with perhaps a GPIO or 2 (maybe for the circuitry to "interrupt" the Sitara without requiring I2C polling?)

[bluehash 1,581]

I think the board will have a great success, if you can pair it up with a real world application... and that application is interfacing your daughtercard to a GSM module(whether USB or using serial -I2C/SPI). Good luck!

$24.99 is a sweet spot, price wise for BBB peripherals.

[yyrkoon 250]

I think the board will have a great success, if you can pair it up with a real world application... and that application is interfacing your daughtercard to a GSM module(whether USB or using serial -I2C/SPI). Good luck!

$24.99 is a sweet spot, price wise for BBB peripherals.

I think in the case of a USB 3G dongle, the connection would be made via USB only, Or perhaps ethernet to a 3G router that has a USB port supporting various USB 3G dongles. I just did a quick amazon search, and what currently exists seems pretty dismal. Extremely high cost( $300-$500 ) for devices that have external antenna capabilities. Or cheap ($20-$50) USB dongles with internal antennas. These cheaper dongles seem to hover around the 21-23Mbit/s GSM bandwidth range.

 

I did also briefly look at 3G modules offered by Adafruit / Sparkfun, but we all know these two places cost wise can be a bit high. So yeah, I do not know . . . I'd probably seriously consider setting up a 2.4-5,8Ghz 'wifi' connection if I could. As while wifi may be considered 'near-field', you can actually reach out quite a long ways if you can get in a spot that has decent line of sight. We've done ~12-15 miles using 802.11g before. In a really 'noisy' area. The same location with newer equipment is actually getting fairly decent 6Mbit service as we speak.

[chicken 630]

There are plenty of 3G USB dongles on AliExpress. E.g. this one:

https://www.aliexpress.com/item/beautiful-white-3g-sim-card-modem/520949234.html

 

The question is of course, if there are Linux drivers for it. But at least Windows 2000 is supported :-)

[dubnet 238]

The question is of course, if there are Linux drivers for it. But at least Windows 2000 is supported :-)

 

W2K?