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Modified Gadgeteer cable for I2C bus


#1

I’m doing this now:


#2

I’m considering getting a pack of 20cm cables and adding two of these along its length, instead.

http://www.mouser.com/ProductDetail/Molex/90635-1101/?qs=sGAEpiMZZMs%2bGHln7q6pm782InRZvVnCoojV3q9JX%2bo%3D

Any comments/concerns in doing so?


#3

Interesting approach. Should work.


#4

@ Architect - Can you give me a “warm-fuzzy” about the connector I found?
Mouser is only a few miles from me, so I get to go there like its a super-bad-a** radioshack from the old days. The will-call ordering is a little funny though; they require a lead-time, pre-selection and payment in advance; can’t quite just “go shopping”…

Radioshack used to have a headquarters just up the road too, but they closed it. You could shop for hours there… :frowning:


#5

After closer look I think it is not the one that will be compatible with Gadgeteer sockets.
It is said in the datasheet that it mates with this one

http://www.mouser.com/Search/m_ProductDetail.aspx?Molex/90663-1101/&qs=sGAEpiMZZMs%2bGHln7q6pm48SVpWlpfsEW3DY5Dwth6U=


#6

@ Kerbal - The one issue I see with the I2C buss solution with the DL40 is that the DL40 has the SDA and SCL on pins 4 and 5 respectively while the I2C devices have SDA and SCL on pins 8 and 9 of the gadgeteer socket.

This is because DaisyLink uses SoftwareI2C while the other modules are using native I2C. Is this something that you have thought about/solved?


#7

@ taylorza - I intend on writing custom firmware for it. I was thinking I would be able to remap the I2C functions to the correct pins while I’m setting up the clocks and stuff. Either that or map I2C off of the sockets altogether… Idk

Admittedly, I haven’t really stopped to think it all the way through yet. I am still just getting up to speed with low-level programming. The ultimate target is arbitrary, but I’d hoped to contribute something back to the GHI community. The DL-40 has kind of been ignored, it seems. I was thinking of plopping, with permission, a big GHI or FEZ logo on my UAV when it’s finished, as well as upload the source.

I might be mistaken though and end up getting batchPCB to make a slightly modified version of the DL-40 which is, aside from the sockets, essentially just a breakout board.


#8

I could not agree more and it is a real pity because it could be a really useful co-processor board for Gadgeteer.

Unfortunately I do not believe you will be able to remap them to the other pins on the Gadgeteer socket. And IIRC the I2C pins are not exposed on the breakout pins of the DL40.

A nice little break out board for the DL40 with gadgeteer sockets would be very nice. Maybe even drop the DaisyLink interface to the board and use SPI to communicate with the mainboard and the breakout board and have I2C available on the DL40 to communicate with the I2C bus like you show in your images.

Good luck with this, I really look forward to seeing your progress. And if you have any questions on the native code for the DL40 don’t hesitate to post a few others here and myself have done a fair amount of tinkering on the firmware for the DL40.


#9

To be honest, I have not actually used a Gadgeteer module with Gadgeteer yet… Are you saying I can use one of the sockets as SPI or that the SPI function is broken out somewhere amongst the 40 pins?

It’s not super-high-priority but I’ll look again, and more closely, at the datasheets in a bit; sleep for now…

Thanks again!


#10

@ Kerbal - Yes, SPI is accessible from the pins on the DL40.

But what I really was alluding to what that it would be nice to have a custom LPC111x based board that has the pins broken out to Gadgeteer sockets and have an SPI slave socket on the board which can be used to communicate with the board. Just putting thoughts to pixels :slight_smile:


#11

@ taylorza - if only you could find someone who knew what you were talking about… :whistle:


#12

I’m going to use (or better try to use) the DL40 for other application and I want to try to implement PAL video out. So I’m not particulary interested in Daisylink protocol, I think, at the beginning, to use on a U socket (it export USART on gadgeteer for fw flash).

Ok … Justin are you buying all M0 chip around?


#13

@ dobova - :whistle:

I’m getting them from the US as locally they seem to be rare as hens teeth…


#14

@ Justin - :slight_smile:


#15

@ Justin - Ahahah :slight_smile:


#16

Check out FRDM-KL25Z, M0+,
Pretty loaded with stuff for only $12.95; tons of pins.

http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=FRDM-KL25Z&tid=vanFRDM-KL25Z


#17

@ taylorza - Hey what about this…

I was going to have Samtec make the cable instead of crimping them on myself, so why not just have them switch the pins on the DL-40 end of the cable? 4-8-8-8, 5-9-9-9

This would allow my DL-40 to drive a downstream hardware I2C bus.
Whatcha think?

Trying to avoid changing the DL-40.


#18

If you to use the daisylink protocol with the DL40 then I suspect that this will not work. Daisylink uses I2C as the underlying protocol, but it layers a protocol on top of that which I do not think will work well with downstream I2C devices (I am no expert here). If you change the DL40 firmware to work as a standard I2C slave then this might work.

One thing I am definately not sure of with regard to the pull-ups. I2C relies on the mainboard to include the pull-ups while SoftwareI2C requires that the modules supply the pull-ups, maybe the fact that the DL40 has the pull-ups will do the job, but someone with more I2C and hardware knowledge would need to chime in here.


#19

1A rating??? Guess that answers my question in another post about using the cellular board and how much current the cables can handle for it! The cellular board module can draw up to 2A. This of course depends on signal strength but during a large data exchange, I suppose these cable could get a little toasty. I’m going to snip the 5V line and soldering a capable power supply line directly to the board. It would be nice for the board to have power in lines to accomidate the high power supply need.