Raspy Juice Exp Board: Rev.1 PCBA

The Raspy Juice Expansion Board Rev.1 PCBA Beta kit is now available at:
http://2-watt-elements.myshopify.com/co ... 1-beta-kit

Raspy Juice is a compact piggyback PCB solution to supply the Raspberry Pi with a regulated +5V via the GPIO header.
Main features are:
1. Wide input voltage range (6-23V) high-efficiency +5V 3A buck regulator with polarity protection
2. Supplies the Pi with +5V through a 2A PTC poly-resettable fuse to the GPIO header
2. RS232-level Raspberry Pi console port either via 2.5mm stereo jack or JST header
3. Real time clock based on NXP PCF8523 with backup capacitor
4. Expansion ATmega168A microcontroller connected to the Raspberry Pi as an I2C slave

Secondary features based off the expansion microcontroller are:
1. RS485 interface with JST connector
2. Additional RS232 interface with JST connector
3. 4x RC-servo output ports supplied with +5V through a 2A PTC fuse.
4. Expansion MCU pins header with +3V 450mA total voltage source, exposing 2 ADC inputs and 6 GPIO pins of the microcontroller.
(The above secondary features were meant for simple robotics experiments.)

Hardware details can be found at https://code.google.com/p/raspy-juice/wiki/HardwareDescription

Code development on Debian Wheezy for the ATmega168A is with avr-gcc, and the microcontroller is shipped with a bootloader so that updating the firmware is through the Raspberry Pi I2C interface without additional accessories. Details of the bootloader and using it is at https://code.google.com/p/raspy-juice/wiki/Bootloader

This beta kit is intended for developers/experimentors to code on the expansion MCU or,
for those just interested in powering the Pi from batteries, other voltage DC adapters and sources!

Let's have some fun!!!

Just got a nice Hack a day plug.
Concerning the new P5 header on RasPi rev2, do you plain to allow pass through access?
I would much prefer to access P5 from above rather then from the bottom of the RasPi. Others people seem to prefer top as well.

Hi MmmPi,

Thanks for highlighting the addition of P5 in the new Raspberry Pi Rev.2 PCB. I like the suggestion of passing the P5 to the topside -- my goal was always to make the RPi-Juice combo height "comfortable for an embedded" enclosure. However, with the current layout of Juice Rev.1, which is chock full of components on the bottom side (see picture attached), this isn't possible.



Maybe in Juice 2? But don't hold your breath because I'd have to re-conceptualise entire sub-sections and component layout to achieve it. Hard, hard, hard .

Y'know, I've been chatting in another forum over how to improve the usability of Juice by having pass-through of P1 (the RPi GPIO header), and I'm going to quote a reply verbatim. (But let's not start a thread here, we can chit-chat over in maybe Add-ons...)

ROTFL. I'll ramble here I wish my comments below can go public for a good fun time
I was an electronics/PCB designer of the '90s (1991~1998) from junior to managerial, designing from peripherals to consumer stuff to embedded computers: connectors and headers on PCB layouts were always our bane. For small and compressed form-factors, they're so big in PCB estate space! . We used to balk at our supervisors; and then when I progressed up the ranks, I used to balk at our execs. Even today, I can meet PCB designers who can say the same thing

Even if an extended pins-header (the type that allows for wire-wrapping or another receptacle to plug over) was used, the height profile of the combo would increase. Moreover, the exposed pins increases the chance of accidental shorts by touchy-feely fingers or dropping metallic screwdrivers -- which is another goal of mine to reduce exposed components and traces on Juice's topside.

I will certainly continue to explore various means to improve the accessibility of RPi's pins while Juice is used. Thanks again for your feedback.

Cheers! Catmaker.

I don't get it what is it

I don't get it what is it

(First, a tiny history: I'm a robotics hobbyist wannabee for many years now).

1a. Treat Raspy Juice as a universal DC supply regulator to the +5V input requirement of RPi, with minimal wiring jungle. If you're using RPi as a "static" computer, then you may power your RPi with other common other-voltage adapters (I use 12V). With upto 2A of +5V coursing through RPi, the USB ports can power hubs and peripherals more reliably without relying on yet other external adapters. (But I've had to circumvent the RPi fuses to do that).

1b. I intend to use my RPi in self-contained robot projects, running off batteries. The voltage of the batteries is usually decided by the type of motors used in such projects. This can vary from 3V to 50V (I'm not sure what others use). Within the voltage input limits of Raspy Juice, the regulator can tap the same battery used to power the motors, to power the Raspberry Pi. No extra battery pack, and no additional BEC (Battery Eliminator Circuitry) are required, reducing wiring jungle. Also, with a simple 2-resistor hack on Raspy Juice, the latter can read the battery voltage and have some software application react appropriately.

2. The RS232-level console port and the RTC -- well, they're just there because the original RPi didn't have them -- but there're people who find these useful (RS232 root console as a last-line-of-defense comms, and RTC for instances where there's no 'net connectivity on bootup for time updates).

3. After being "comfortable" with the RPi and its attached peripherals powered reliably, then the expansion microcontroller can be explored: this was mainly for robotics experiments of actuation, movement and locomotion. Up to 4 common RC servos may be attached, powered, and controlled directly by Raspy Juice, again with minimal wiring jungle. No additional wiring to headers, through IC chips on breadboards, or additional batteries or BEC's or power supplies or adapters. Meccanocally, I feel that it can already be time consuming to fix RC servos to the things I want to move. (But it is fun to hear quickly after power-up, "Oooo, it moved!" )

3b. The servo ports can also be interfaced directly to appropriate ESC (Electronic Speed Controllers) to control more powerful motors, like those used in model helicopters, quadrocopters, planes, tanks, powerboats... I don't play with such models, so I leave these to a user's imagination.

4. For slightly advanced projects, then the microcontroller's RS485 and RS232 ports may be used to interface to expansion servo/motor/relay controllers, daisy-chainable Dynamixel servos (albeit expensive), and other types of sensor and control modules.

5. For more advanced projects, then the microcontroller's expansion pins may be used to interface to other circuitries or IC chips, but this requires some firmware programming skills of the AVR microcontroller. Such things would probably include joysticks, accelerometers, GPS modules, RF transceivers...

I really really hope to answer your question: but similarly with other multifunction expansion boards available to the Raspberry Pi, there are too many possibilities that can only be left to a user's needs and imagination.

Warmest Regards
catmaker.

catmaker
I love the concept. It has all the things i wanted.
Ordered mine over the weekend (10Nov).
It says it is a Kit - Not assembled? Ok, i've got solder.
is the schematic available?
What size supercap is the rtc on? any estimate on hold up time.
if you chose the smallest button, i calculate about a week.
10uA/hr at 50nA = 200 hr

It says it is a Kit - Not assembled?

Hi densipe,
Thanks for your support and order.
The Raspy Juice Rev.1 Beta PCBA is pre-assembled, so there's no soldering required of its SMT components.

The 'kit' (thanks for highlighting!) in the web-shop really refers to:
1x Raspy Juice Rev.1 Beta pre-assembled PCBA board
1x 2-core power wire with Molex header assembly
2x 3-core signal wire with JST header assembly
1x 10-pin header (this isn't soldered onto the board because some users may not want it).

The schematic isn't publicly available yet. It will be on the project page after some refinements.

You're right: the supercap is 0.22Farads, which holds up to about a week.

Thanks again
catmaker.

I received a Raspy-Juice board, and have been trying to get the RTC module working. I built a custom kernel to add support for the PCF8523 device, and finally got it recognized as hwclock. Unfortunately, shortly after it started messing up. I received errors that it had an invalid date/time, and it wouldn't let me set it. Even stranger, now when I issue a i2cdetect -y 0 command, every position on the i2c shows its corresponding number, like every position is occupied, when it should show -- for everything except 48 and 68. Before it was showing it correctly, but now all positions look occupied. Any idea what could be causing this? I already tried re-writing the firmware to the AVR (had to do the manual reset).

when I issue a i2cdetect -y 0 command, every position on the i2c shows its corresponding number, like every position is occupied

In my earlier days of this I2C dev for this Juice, I've seen this style of errors before. I think it was caused by a missing, shorted or grounded I2C pin. I'll attempt to re-create it...

It is weird though, it was working and then it just messed up, i didn't modify the hardware or solder on/to it or anything

Hi magic_man185
a. I re-created a similar status report of "i2cdetect- y 0" where all positions are filled. This can be caused by shorting SDA to GND.
b. I've a unit here that didn't pass testing, also showing the same output where all positions are filled. However, I've probed it and SDA isn't shorted to GND. I will continue investigating, and see if this is recoverable. May I PM you please?

Thank you for such a quick response, and for taking the time to investigate. Yes, PM would be fine. Which chip did you short SDA to ground in order to get this to happen, or does it matter? When you do this does it permanently cause this status, or just while the pin is grounded (I would imagine it is just temporary). Should I check the two chips and see if for some reason SDA is connected to ground?

Which chip did you short SDA to ground in order to get this to happen, or does it matter?

a. The SDA snd SCL are bussed to all chips, so it doesn't matter. On Raspy Juice, there is an I2C debugging pinout JD1, alongside the GPIO header, those are the test-points I perform the grounding. (For HW testing only: Grounding SDA/SCL permanently will not cause damage. However, tying SDA/SCL to +3.3V must be done briefly because it will stress the "talking" chip output drivers).

When you do this does it permanently cause this status, or just while the pin is grounded

b. For a good PCBA unit: The poor status is only shown for the duration whilst SDA is grounded. When this grounding is removed, the status returns to normal.

Should I check the two chips and see if for some reason SDA is connected to ground?

c . With your un-powered unit, you could check with a multimeter to see if SDA is shorted to ground. However, I suspect that it will not show as a short, because I have just one unit here that shows the same symptom but it has no hardware error of a grounded line. I too have re-flashed this unit with the upgraded firmware.

catmaker

can you make a recommendation on a case that will accommodate the RPi/RaspyJuice combination?

Dennis

can you make a recommendation on a case that will accommodate the RPi/RaspyJuice combination?

Hi Dennis,
I, uh, leave my RPi's raw and uncased, because I do quite a bit of probing. At a local Jam meetup, I was offered a good-looking white plastic enclosure from a member's extras. We think the internal height accommodates the combo including the JST connectors, but the top half has inner spines on both sides that prevented us from pushing in the combo then.

[edit: added] The casing was "MULTICOMP - MC-RP001-WHT - ENCLOSURE, RASPBERRY PI, WHITE" from element14.
I think I'll order a couple and nibble the spines off. Let me try first, please?

Adnan

I have one of the multicomp cases as well, and although I haven't removed the inner spines, I came to the same conclusion that it most likely would fit if those were removed. If you would prefer, I can just cut the spines off of the one I already have and test it, that way you don't have to order one and wait for it to arrive. I should be able to do this on Monday.

If you would prefer, I can just cut the spines off of the one I already have and test it, that way you don't have to order one and wait for it to arrive. I should be able to do this on Monday.

Thank you, magic_man185, that'd be really nice.
I've checked the items here locally, and they have over-the-counter stock of the white and black models.

I was also pleasantly surprised that there's a clear see-through perspex model, but the stock is only available in the UK. I'm going to place my order for the clear-perspex on Monday -- it's finally time to build a home showcase unit and put it beside the living-room TV!

The casing was "MULTICOMP - MC-RP001-WHT - ENCLOSURE, RASPBERRY PI, WHITE" from element14

Oh, this is a disappointment: I've just tried to mount the Raspberry Pi - Raspy Juice combination into the above enclosure and they will not fit. The JST headers are 1.5mm too high for the enclosure to snap shut. The inner spines that I've nibbled off to allow a Pi-piggyback board, also serves as height-control standoff for the enclosure's front side. So if these are missing, the enclosure's front-side may "over-close".

Just as an experiment, I will snip off the JST headers on one of my older dev Raspy Juices and see if there are any other interferences.

catmaker

The casing was "MULTICOMP - MC-RP001-WHT - ENCLOSURE, RASPBERRY PI, WHITE" from element14

Things I had to do to Raspy Juice to make the above enclosure snap shut:
a. Nibble the inner spines of enclosure's upper half
b. Drill a hole on the enclosure's upper half for the RS232 console 2.5mm stereo jack
c. Make a tiny cutout near the USB ports for the power wire
d. Nibble off the top of the JST headers on Raspy Juice
e. Nibble off the top of the Molex power header on Raspy Juice

Raspy Juice isn't pretty anymore, but the enclosure finally snaps shut.

It looks like there would be problems if you ran cables to all of your JST connectors.
Probably, not an issue. If the RPi/RJ is using those connections, it is probably embedded in a larger assembly.

Dennis

You beat me to it. I tried it out yesterday, but I didn't have a chance to post my findings, which were the same as catmaker's.

Hi magic_man185,
Thanks for trying yours too!!! (With a slight detour, the element14 counter here locally is on my way to my workshop, so I dropped in to purchase the enclosures).

Despite "losing" my older Raspy Juice after all those snips-snips, I am actually quite pleased when the enclosure snapped shut.

The casing was "MULTICOMP - MC-RP001-WHT - ENCLOSURE, RASPBERRY PI, WHITE" from element14

I AM going to use this Raspberry Pi - Raspy Juice - MC-RP001-WHT combo as my living room showpiece. Thanks again! catmaker

I think the Juice has all that I am looking for. I need to run from a 12V supply and communicate with a master over RS485. The master is using a mode similar to MODBUS RTU, so I need to detect End Of Transmission with 3.5 character silent intervals. That will require some work with the AT Mega - this device is new to me, but as I've developed a complete solution on 8051 based dev's previously, this shouldn't be impossible (I hope).

In my application, the master on the RS485 bus must be replied to within X milliseconds with either an instruction packet from over in Linux userland, or in the case of no userland instruction, a standard acknowledge back to the master.

I need to spend some time thinking about this, but it's nice to see an add-on out there that may fit my needs - I will need to replace power and RS485 connectors with screw terminals though, so hoping the thru-hole pitch is similar.

I received a Raspy-Juice board, and have been trying to get the RTC module working. I built a custom kernel to add support for the PCF8523 device, and finally got it recognized as hwclock. Unfortunately, shortly after it started messing up. I received errors that it had an invalid date/time, and it wouldn't let me set it. Even stranger, now when I issue a i2cdetect -y 0 command, every position on the i2c shows its corresponding number, like every position is occupied, when it should show -- for everything except 48 and 68. Before it was showing it correctly, but now all positions look occupied. Any idea what could be causing this? I already tried re-writing the firmware to the AVR (had to do the manual reset).

Hi magic_man185, and All
I've re-created the problematic issues discovered by magic_man185: the Raspy Juice service firmware Rev 156 on power-up occasionally causes the SDA line to be pulled low permanently, preventing proper operation of the I2C interface thereafter. However, you may checkout an older revision of the service firmware with:

Code: Select all

svn checkout -r 134 http://raspy-juice.googlecode.com/svn/trunk/ raspy-juice.134

and follow the instructions on Updating the Firmware on the Raspy Juice Google project page.

I am still investigating the cause of this.
catmaker

I think the Juice has all that I am looking for. I need to run from a 12V supply and communicate with a master over RS485. The master is using a mode similar to MODBUS RTU, so I need to detect End Of Transmission with 3.5 character silent intervals. That will require some work with the AT Mega - this device is new to me, but as I've developed a complete solution on 8051 based dev's previously, this shouldn't be impossible (I hope)..

Hi stuarty,
I'm happy to hear Raspy Juice may suit your needs. From the above, I understand that you're going to treat the Raspberry Pi-Raspy Juice combo as a Modbus RTU slave. I think you're right about it: for the 3.5 character EOT detection, and the X millisecond response back to the master (after some interaction with your userland app) is best implemented in the AVR microcontroller service firmware.

What RS485 speed do you think you'll be communicating at?

I will need to replace power and RS485 connectors with screw terminals though

The pitch of the JST and Molex connectors is 2.5mm with 0.9mm holes in the PCB. I have found before Screw Terminal Blocks which are 100mil pitch, through-hole PCB-mounted: something like this http://www.digikey.sg/product-detail/en ... ND/1153264 . I hope this helps.

(Sorry for late reply -- just I've found a firmware bug which requires attention). catmaker.