Raspberry Pi Fork?


#1

I know there have been a couple mentions in various threads of switching the BeagleBone for a Raspberry Pi. From what I can tell, either unit is fully capable, with the latter costing a bit less. Should development for the Raspberry Pi (and, hopefully, Pi-specific software and SD card images) be included in the main OpenROV forums, wiki, etc. or should we establish it as a fork from the original project?

I imagine the two will maintain major similarities, but some alterations (adapting the Cape for the Pi profile, making use of the different I/O options, probably changing the electronics chassis design to accommodate) might warrant the split.


#2

This is a great point. I think we should definitely maintain it on the Wiki/Forum. It's important that the project remain agnostic to the different embedded system architectures - things are changing so fast, that we'd be really shooting ourselves in the foot if we get too attached.

I just added it to the Under Development page on the WIKI. http://wiki.openrov.com/index.php/Under_Development#OpenROV_Cape_.28Adapted_to_Rasberry_Pi.29

How do you think this effort should be documented/coordinated?


#3

If the Ras-Pi version takes on, i could probably provide some help with designing a adapter board for Pi to Cape connection.

One could consider making a direct cape for the Pi aswell, with most as possible equal, so arduino code have the same in/out functions.

The most ideal would to have a universal cape platform, but i think we are running out of space in the cape board. Ie to have the Pi header available, and one could just solder in a connector, and reconfigure dip-switches or resistors. Like the cape can accomodate a Arduino shield with some small mods.

I have a Pi laying around, and when i get a cape, i can see if not we can do some magic with pcb software and some smart connector layout later on.

Documentation wise i would suggest to add some forums for this OpenROV-Pi work, to keep the discussions and knowledge gathered. Ie a github repo and a subforum. and possibly a sub-part of the wiki


#4

I agree, some separate forums and a separate repo would be a good idea. I know the wiki already has a Raspberry Pi page, but I think right now it's only focused on getting the standard code running on the Pi.

I think the best thing to do at this stage is organize the ideas presented thus far in various forums into one central place, as they are pretty scattered right now. It would also be great if some of the people who have already been experimenting (I know Dan Myers had a blog post a couple weeks ago) could share what progress they've made. If http://wiki.openrov.com/index.php/Raspberry_Pi is still accurate, we should be able to get a working image online pretty soon.


#5

Other interesting small low power computers to track for ROV:

The MK802 features an Allwinner A10 ARM Cortex-A8 processor, 512MB to 1GB of RAM, 4GB of storage, and a microSDHC card slot. It has mini HDMI and mini USB ports, as well as a full-sized USB port.

http://liliputing.com/2012/08/mk802-ii-android-4-0-mini-pc-now-shipping.html

Rumors are that these small arm based systems may have quad-core offerings next year.

We can look at other form factors for the cape if these systems-on-a-stick become interesting.

Jim


#6

Just saw Dual core is shipping now for L59.99 from UK.

http://store.cloudsto.com/dual-core-rikomagic-mk802-iii/rikomagic-dual-core-mk802-iii-4gb-flash-dhl-express-shipping-175-detail.html

They come loaded with Android OS. I think they can be booted into Ubuntu as well - you would have to configure.

They run off of USB power - no details specified as to how many watts. Should be low since ARM based.

Technical Specifications

Model MK802 III Dual Core

CPU RK3066 Dual Core - Cortex-A9 Up to 1.6GHz

GPU Quad- Core 2D/ 3D/ OpenGL ES2.0(AMD Z430)/ OpenVG1

OS Android 4.1

RAM 1GB DDR3

Memory 4GB Flash

Expansion Micro SD T-Flash(Maximum support 32GB)

Video Format WMV/ASF/MP4/3GP/3G2M4V/AVI/MJPEG/RV10/DivX/VC-1/MPEG-2/MPEG-4/H.263/H.264/1280*720P HD 30 fps, 1080P/720*480 D1 30fps

Audio Format MP3/WMA/APE/FLAC/AAC/OGG/AC3/WAV

Picture format Max.8000x8000 JPEG BMP GIF PNG

WiFi 802.11 b/g/n

Flash Supports flash 11.1

Ports HDMI(male),Micro SD slot, USB host (full sizeUSB), USB power port(micro USB); LED(Blue)

Unit Size (mm) 90mm*40mm*13mm (3.54 x 1.57 x .51 inches)


#7

These small MK802 computers are really cool, but they lack some functions that is needed for the current layout of the OpenROV:

-Cabled ethernet

-serial ports(seems like some have this)

-some GPIO ports for interfacing against Arduino/Atmel MCU

-i2c / spi interfaces for expansion later on.

we could probably do without the native gpio, and get some with a gpio circuit connected to i2c or spi interface.

I've worked some with the TS-7500 from http://www.embeddedarm.com

And this has ALOT of expansion capabilities in a small nice package. the price is not that bad either.


#8

Right.

And Arduino was never the most technically capable microcontroller - it just had the best community. It seems like Rasberry Pi is building a similarly passionate community, and it'd be great to attract some of those folks to help with OpenROV - the more the merrier!


#9

Arduino (atmega168/328) is a good platform to startout with, the community around the mcu is just incredible.

one can expand really much with ie pwm expanders, multichannel ADC chips etc. as long as we dont calculate that much, and have a reasonable polling rate on the data.

things i think the community could want is probably: leak detector, pressure/depth sensor, compass module, manipulator arm, external lights, lateral thrusters and etc.

A really nice thing with the Raspberry Pi is the camera module thats right around the corner. the gpu is also said to have a buildt in overlay function, so the telemetry data could be written on the camera image. thats really cool!


#10

I'll play with the MK 802 IIIs when it arrives. The tradeoff here is lots of cpu power/memory, etc + Android (if we want to go that way). Would need to connect the cape with usb (newer atmega32u4 - used on leonardo might be interesting for next gen cape. Has usb on chip and also has 12 analog inputs).

If we can keep our sw stack modular, we can accommodate multiple combinations of hw for different needs. I expect to see lots of new hw choices on the linux side due to folks taking advantage of the chips coming from the mobile/tablet world. we can rely on the cape for the i/o with the real world.

i would like to try pressure and compass (or full imu with gyro, etc.) next, once i get in the water. i probably will try some static depth tests (no electronics on board) to give me some confidence in the seal. steve identified a depth sensor and imu that are interesting. we are almost out of analog i/o with the current cape and may need to use i2c based components for expansion.

Jim


#11

I have a spare Rasberry Pi I can use to help test things, I was lucky enough to be able to get two of them in the beginning.

Roo


#12

Hi gang,

I'm the lead for AlaMode which is an Arduino clone for the Raspberry Pi.

I think it already has most of what you need.

You can communicate between the Pi and the AlaMode via Serial, I2c and SPI

It has it's own micro-sd (for painless arduino sensor datalogging), RCT

and breakout headers for Servos and analog sensors.

Wanna try it? We'd be willing to donate an evaluation unit to your project.

If it works out, we can probably give you a generous discount for your store.

Let me know,

Kevin


#13

Hey Kevin,

That'd be awesome! As you can see, there's huge demand for it here. Sending you a message with mailing info.

David


#14

Hi Kevin,

I saw your AlaMode last week, and i posted the link in this thread: http://openrov.com/forum/topics/raspberry-cape?commentId=6365107%3AComment%3A33386

I've looked over the shcematics on your card and our cape, and there are very few diffrences so there is not much hacking that would be needed to get basic functionality.

Thumbs up for the support!


#15

I would be interested in purchasing one and then testing anything as necessary as I will begin my ROV build when I get home this next time off (after Jan 25), resources are not generally an issue for my projects, more than happy to help progress any of these projects. Please PM if interested.

Humbly,

Roo


#16

From what I'm seeing, the only thing lacking in the AlaMode is a high-current switching power supply, with the one on the ROV cape supplying 3A compared to the 1.5A for this board. Does the AlaMode have the capability to power the RPi from its regulated barrel plug input? If so, the 3 ESCs have their own 5v power supplies on-board, available through the 5v line of the PWM cable. That could be used to supply the current to the camera-rotation servo, making sure there aren't any dropouts for the ATMega or RPi.

Unfortunately, It seems the "Where to buy" links are either nonexistant or 404, so I'm unaware of the cost to try/buy one. I recently got a RPi, and getting an arduino interface working to test out motor control would be another step in the right direction.

Oh, and the name AlaMode is pretty clever, too.


#17

All of our distributors are out of stock right now. but I have a couple in hand for worthy projects..

This scenario wasn't in our minds when we designed it, but you should be able to put the jumper on for powering the AlaMode from the Pi, put in regulated 5V into one of the 5V0 ports and power both the Pi and AlaMode externally.

The retail is about $50.


#18

Correct me if I'm wrong, but doesn't the barrel plug input accept anywhere from 6-20v and switch it down to 5v using the NCP1117ST5, much like the default arduino? Then as you said, put the jumper from the Pi's 5v to the Alamode's 5v, and instead of going from Pi-Ala, it'll simply go in reverse and power the Pi. What I'm not sure of is whither the Barrel-plug input has the possible connection to the RPi to power it from the 11.1/12v batteries of the ROV.

Also, in order to drive the headlights of the ROV, an external transistor circuit will have to be made (which shouldn't be too hard) to add PWM to a 12v line.

$50 is right around the realm of the ROVcape, so it isn't at all unheard of. Plus, with the possible discout for ROV users, it would be an extremely viable alternative to designing a completely new board just for the RPi.


#19

Sorry, if I wasn't clear. You wouldn't use the barrel plug for regulated in. There are a couple of other points on the board where you could inject 5V including the GPIO extension header. (Also there's a header for AREF that you could use.) Like I said, it wasn't in our minds when we designed it, but it should work. I'll try it and let you know.


#20

I'm not talking about regulated input, I'm talking about unregulated input from the 12v battery array. Is there a point on the board in which you input unregulated power (6-20VDC) and it powers the board via a switching converter (regulating it to 5v)? On the pictures of the board it appears you have a spot for a barrel plug, and in the schematics you have a switching regulator inline with that, but the physical female barrel port is not populated in the pictures.

Edit: sorry if I was not clear; the regulated 5v I was talking about using from the ESCs was only to power the servos, not the rest of the AlaMode and RPi.

Essentially, I want to power the AlaMode and RPi with unregulated power, inputting it into the AlaMode and injecting it into the Pi via the 5v GPIO pin.

I look forward to your test results.