Sorry Jim, I haven’t really caught up on this thread since it restarted this month. I’ll take a look and comment on the cap and other design issues that jump out at me.
Mike
Kurt,
Some quick opinions on questions that you have asked.
- I agree with Jim that a beefy cap is not needed for the Vservo input. Some 0.1uF caps sprinkled around on Vcc are good though. It looks like you have them near the headers. I would add one near the speaker as well.
- I think there should be a power LED, with a 1K resistor.
- I wouldn’t worry about the 3.3V selection, just recommend the users stick with 5V when using this shield. In fact, depending on the clock rate on the Mega, it might not be specified to work at 3.3V
- Yes, definitely have resistors on the LEDs, but you won’t need external pullups on the switches.
- I usually use a Vcc pour on one layer and ground pour on the other. A little extra capacitance never hurts in the power supply.
- I would not worry too much about using this board with a regular Arduino (non-Mega). That role would be filled by the BBduino Jr, right?
It’s hard to tell from the board images what the pinout of the I2C connectors is, and how the pullups are managed. Can you give a brief description? I will try to match the pinout on the new SSC-32, which will have an I2C header.
Thanks,
Mike
Thanks Mike,
I like all of the suggestions I can get.
-
I dropped the large Cap. Will add one near the speaker as you recommended.
-
Will add the power Led as you suggested.
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Yep for now it is much easier to punt on the 3.3v. If this were a single board where I had access to the switch, than maybe I could use the information.
-
That is what I decided on the LEDS and switches as well
-
I will change the top to VCC instead of ground as well.
-
I2C - Right now, I am simply cloning their connector (except giving them a set of male connectors instead of the Arduino type. Details on the Seeeduino Mega board is up at: seeedstudio.com/depot/seeedu … th=132_133
They have a WIKI for this board. From the WIKI you can download a set of EAGLE files for this board: garden.seeedstudio.com/images/a/ … _v1.23.zip. Looking at their schematic it looks like they simply bring out SCL/SDA, +5v, and GND. So far I don’t see any pullups other than the weak ones that are internal to the ATMEGA. Should we add some or assume that the user will want to choose their own?
Thanks again
Kurt,
Yeah, it looks like they didn’t include any pullups in the Seeeduino Mega. I2C needs fairly strong pullups (4.7K is common) to achieve good speed, but they can be anywhere on the bus. I was thinking about putting in jumpers to enable pullups on the SSC-32 USB version.
Mike
Maybe I should duplicate that for the I2C as well. It would make it easier to use the I2C.
Also seeing the different threads talking about Lipos and needing a close eye on voltage. I was thinking about maybe adding a couple of jumpers with shunts to optionally connect VServo and Vin to 2 analog pins, through voltage divider. Maybe someday I will get brave enough to go to a Lithium battery, maybe something like an LFP.
Kurt
OK, I think I did most things other than add to I2C. Not sure where to fit the extra jumpers 
The Zip file has Schematic, Brd, plus PDF prints of them plus gerber stuff…
What do you think?
Kurt
Botboarduino Mega Shield.zip (346 KB)
Hi Mike and Jim,
I found a couple of ways to get the I2c Pull-up jumpers in. Here is one of them.
I only show the top. I shifted the Comm plugs up to make room and added the jumpers between them and the Analog 8-15 pins, which I was able to route the lines. Another option would be to shift up the Analog Male pins (can not move up the female pins as this is where the mega board had those ins. Then I could probably put the jumpers down near the I2C connector. Thoughts?
My next step will be to figure out the parts list, such that hopefully I won’t screw up again and not have valid parts.
Kurt
Kurt,
Looks good. I have been thinking a lot about I2C connections, and would like to get opinions about some different options. Here are a couple of links to write-ups on I2C connection “standards” that are reasonably well thought-out. I have one of the 4-pin Amp 7-215079-4 connectors mentioned in the first link. It has the advantage that you can make daisy-chain cables from 4-conductor ribbon cable easily by pressing IDC connectors into the middle of a length of cable. It would be nice to settle on a standard connection sceme for Lynxmotion I2C.
i2cchip.com/i2c_connector.html
acroname.com/robotics/info/s … c/iic.html
Thoughts on all this?
Thanks,
Mike
Hi Mike,
I like the idea of a standard I2C hook up. I have thought about using the brainstem (2nd link) as I was thinking there would be several Acroname (Daven-tech) devices that support it, but then did not find many and it had 2 extra connections which were not used… Also I was looking at these as I could use standard servo wires to connect, although I had to steal an extra wire from somewhere for the 4th connection…
The first one looks interesting, as you can support 4 or 6 wire connections, not sure if there is any reason for us to go to 6? Could hook up one of the additional IO lines to control resets (if any devices care) and maybe hook up VServo to the other power line. I do like the idea, that for example if you stack 3 devices you can simply can take your ribbon wire and slip on as many connectors as you need at the spacing you need, which would help in minimizing cable lengths. So it would not be difficult to switch to these.
Jim or Mike your call…
Kurt
I don’t fully understand I2C nor its common wiring schemes. I will comment that wire assemblies are very inexpensive, and should not limit the choices. I am leaving it up to you guys.
Hi Mike,
I played around with the design using the connectors you mentioned. Currently looks like:
I did a quick and dirty component for the connector. If I am not mistaken it has the 4 pins plus a polarization hole, which I don’t have connected to anything.
I think I am pretty close to sending it off and see if it works.
Kurt
I am working on the parts list now. So far it looks like:
Digikey Part Number CNT Manufacture Description
102-1155-ND 1 CUI CEM-1206S BUZZER 2.4KHZ 12MM PC MOUNT
160-1426-1-ND 1 Lite-on LED GREEN CLEAR THIN 0805 SMD
160-1427-1-ND 2 Lite-on LED SUPER RED CLR THIN 0805 SMD
160-1428-1-ND 1 Lite-on LED YELLOW CLEAR THIN 0805 SMD
277-1721-ND 1 Phoenix Contact CONN TERM BLOCK T/H 4POS 3.5MM
399-1168-1-ND 7 Murata CAP .10UF 25V CERAMIC X7R 0805
BAV16WDICT-ND 1 Diodes DIODE SWITCH 75V 400MW SOD-123
EG2510-ND 4 E-Switch SWITCH TACT 6X3.5MM H=4.3MM 130G
MMBT6428TR-ND 1 fairchild TRANSISTOR GP NPN AMP SOT-23
RR08P4.7KDCT-ND 2 Susumu RES 4.7K OHM 1/16W .5% 0603 SMD
RR12P1.0KDTR-ND 3 Susumu RES 1.0K OHM 1/10W .5% 0805 SMD
RR12P10.0KDTR-ND 2 Susumu RES 10.0K OHM 1/10W .5% 0805 SMD
RR12P30.0KDCT-ND 2 Susumu RES 30.0K OHM 1/10W .5% 0805 SMD
RR12P390DTR-ND 3 Susumu RES 390 OHM 1/10W .5% 0805 SMD
RR12P4.64KDTR-ND 1 Susumu RES 4.64K OHM 1/10W .5% 0805 SMD
RR12Q49.9DTR-ND 1 Susumu RES 49.9 OHM 1/10W .5% 0805 SMD
A26509-02-ND 3 CONN HEADR BRKWAY .100 02POS STR
A34344-02-ND 1 2 CONN HEADR BRKWAY .100 04POS STR
A26509-03-ND 7 TE Connectivity CONN HEADR BRKWAY .100 03POS STR
A26509-04-ND 9 TE Connectivity CONN HEADR BRKWAY .100 04POS STR
A34344-04-ND 8 TE Connectivity CONN HEADR BRKWAY .100 08POS STR
A26509-08-ND 1 CONN HEADR BRKWAY .100 02POS STR
A99472CT-ND 1 TE Connectivity CONN FMALE-ON-BRD 4POS VERT T/H
1 4 HDR-1x4
1 6 HDR-2X3
2 6 HDR-1X6
10 8 HDR-1X8
The problem I am having right now is for Long stackable headers. I don’t find any at Digikey or Mouser. If I look up at the site: ladyada.net/wiki/partselector/header?s]=1x8#female_header
It tries to give you different sources for the connectors. The one it gives for the shields is from 4ucon, which you can order directly from Taiwan. But it turns out these are what Sparkfun carries. For my prototypes I may simply order some from them.
Kurt
So I went ahead and ordered myself 5 boards to be fabricated. For testing purposes I also ordered 2 more Seeeduino Mega boards from NKCElectronics, I also ordered 5 of their shield header kits (2 1x6, 2 1x8, 1 2x3) as I have not found a good resource for ordering the 2x3s (Spark fun sells the 1x6 and 1x8). I ordered the rest of the 1x8s from Sparkfun. I have not found any 1x4 except from 4uconnector.com/online/index.asp which is where Sparkfun gets theirs. But the Minimum order is something like 1000 units… I also ordered the remainder of parts from Digikey (I had to make the same substitutions as was done for Prop board…)
I figured since there are no small chips to solder I will be able to do this myself for 1 or potentially all of them. Have WSL soldering station, plus will have Hakko FX-888… Did order some new solder wicks, flux, …
The zip file has Dip Trace Design files, Gerber files, Parts List (XLS), and PDF files showing the board and schematic.
Kurt
Botboarduino Mega Shield.zip (457 KB)
Kurt,
This looks good. You will learn a lot from building the boards. Don’t be afraid of SMT assembly. Even packages like the FT232 are not bad with some patience and a good magnifier.
The Hakko is a good choice IMO. It is basically an update to the 936 that I own, and should be a good reliable station. Your and my setup will be very similar. I keep a big tip in the Hakko for through-hole, and a fine tip in the Weller for small SMT. I think the short grip-to-tip distance of the Weller (better control) is more important for fine work. If I could justify the cost, I would get 2 of the Wellers because I think they are slightly better performers, but the Hakko is outstanding bang for the buck.
Mike
Thanks Mike,
I think I have all the parts now for these boards. The boards should have shipped yesterday or today so by early next week I should have them and can start to assemble early next week. The Hakko arrived yesterday so I will test it out by soldering on the extra connectors to the 2 Seeeduino Mega boards I ordered for my testing. I now have 5 of them (one with a torn off USB connector that someday I may try to fix. May simply hook up a MAX232 and a DB9…)
Jim/Mike/…
Once I assemble one or more of these shields and start some testing, would you like me to send you some/all of them? Jim I could send along one of my Seeeduino boards, if you would like to play with it. I know that you are pretty busy these days, especially having fun and designing some new robots 
.
Do you know what the status of the Botboarduino Mega board from Andrew? Last I heard was he needed to replace the processor. Could not tell if it was a problem with the actual board. Should we try again to build his current designed ones? Or should we start off with the Eagle design files for their MEGA boards which we can get from their WIKI and again simply change the board size and hole locations.
Kurt
Hi Kurt,
Please don’t send me the seeduino board. I will need to contact them to see if I can get some sort of distributor discounts in order to carry them. If I can work something out then I will order some to use in tutorials or assembly guides, but before this happens I need the shield. I will sell the shield by itself if I can’t negotiate a reasonable agreement with the seeduino people. Either way I want to make the Botboarduino Jr., the mega board, and shield.
Andy is out of the picture. He told me the work he did is mine. But he considers the work to be the data and no physical samples will be provided. Trossen is having a really hard time right now. They have laid off people and are down to Matt, Andy, and one other guy. I’m hearing they are having trouble making payroll. So he has no time.
I’m not knowledgeable enough to make this decision. I will say he did intend to do a cool thing, but he just had to change his priorities. I just don’t know if it’s better to start over from scratch. I do have the funds to make all of these product a reality.
The boards arrived. It appears like some of my text is too small to work on the board, but they look good enough to experiment with:
So it looks like it is about time I start to see how many mistakes I made on this one: 
With the SeeedMega board all of the ones I have purchased they only soldered in the standard Arduino Headers 2 on top, 2 on bottom plus ISP. They provide the rest of them for you to solder in yourself. May be good if you can have them assemble them there… They probably have some discounts as the place I purchase them from they do offer a discount:
1-9 : $42.50
10-99: $38.25
100+: $34
Sorry to hear about Andy and Trossen. I wondered as I have not seen any posts by some others who were very active before.
Kurt
Well, I did my first pass at trying to assemble a board. I am both slow and not good at soldering, especially those tiny little SMD components. I would not be surprised if I screwed up a few of them. Also had a couple of parts go flying on me. (May have to buy a couple more resistors and caps )
Here are a couple of pictures:
I have done a few simple tests to make sure I don’t have a dead short between VServo and GND. Will also check that with some shunts in and check +5V as well… Then the fun will be to align all 100+ pins between the shield and the Seeeduino mega board and try to plug it in…
Kurt
When I did assemblies like this in the past I took an exacto knife blade and put it into one of those alligator clip (extra hand) thingies. I would use it to hold the tiny part in place during the soldering process. From the look of some of these connections they’re probably “cold” which means not a good connection.
I have used some of the no lead solder and couldn’t really make good connections with it. What are you using?
I spent a good 15 years of my life soldering 8 hours a day. But I’m better at doing it then explaining how to do it. lol
Perhaps Mike has some suggestions as well.
Any hints would be great! Like what temp works best or the like. The solder I was using is some stuff I bought maybe 5 years ago from Digikey. It is a 1lb spool .025 solder from kester. DOM is 3/23/05 Not sure if it is lead free or not. May have to try the exacto knife trick. I have seen elsewhere, where some use a drop of crazy glue, but I am not sure about that one. Never had much experience building circuits before, mostly did things like repair wiring or the like so I am sure I am doing lots wrong.
Again it would not surprise me if there are some cold ones. but hopefully there is enough not bad that I can test out the circuits to see what I really fubred on… There are sure a whole lot of solder joints here
Kurt
Kurt