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31  Community / Bar Sport / Re: connectors on SMD modules [follow up: do elecrow, itead or seed do half vias?] on: August 23, 2014, 10:32:40 pm
Their routing doesn't look too accurate, but overall it seems like a good result.

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Rob
32  Using Arduino / General Electronics / Re: PCB jumpers on: August 23, 2014, 06:50:03 pm
OK, good one,  keep DRC happy with the track on the other side that you will never physically make.

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Rob
33  Using Arduino / Networking, Protocols, and Devices / Re: Dynamically define communication channel for I2C on: August 23, 2014, 05:57:12 pm
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once you connect more than one on the default address, this will not work anymore.
That probably makes sense as AFAIK you can't have multiple slaves talking at the same time.

Why not add a single slave at a time and have it store it's address in EPROM?

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Rob
34  Using Arduino / General Electronics / Re: PCB jumpers on: August 23, 2014, 05:45:29 pm
In Altium I would create a pad as a component (I already have many different ones I use for test points) then drop two on the schematic.

But how to do that on the PCB and have it back annotate to the schematic I don't know, not even sure if it would be possible. I think it would be just as easy to swap back to the schem and drop the pads as required.

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Rob
35  Using Arduino / Project Guidance / Re: Multicontroller on: August 22, 2014, 08:46:41 am
I think you need to troubleshoot the problem, there's no way to decide what to do before knowing what needs to be done.

If that PIC is the only CPU then presumably the entire system can be controlled from that 28-pin socket and a 328 or larger could to the job by emulating the PIC. So you could make an adapter to plug a Uno (or whatever) into that socket and start writing code.

Or you could learn how to use a PIC.

But all that is a waste of time if it's just the LCD.

GOTO Line #1

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Rob
36  Development / Other Hardware Development / Re: Shield for programming Uno over RS485 signal lines on: August 22, 2014, 02:47:12 am
Lookin' good. I was about to ask you about the DIN clip you are using, now I don't have to smiley

According to a couple of Intersil data sheets

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Short networks using the 250kbps versions need not be terminated, but, terminations
are recommended unless power dissipation is an overriding concern.

I am tempted to try without termination for slow speeds, but then I just found the LTC2854/2855, it has a 120R internal resistor controlled by a pin, so I can decide at run time if it's required.


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Rob
37  Using Arduino / Project Guidance / Re: Remote programming a due on: August 21, 2014, 06:42:51 pm
I haven't looked at the Due for ages, but IIRC the SAM can boot directly from the UART, on the Due this connects to the 16u2 which in turn connects to USB, but maybe you can hack your own connection and talk directly to the UART.

The protocol is pretty simple I think so having done that (and added some line drivers) should be able to do it remotely.

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Rob
38  Products / Arduino Due / Re: Dynamic memory allocation in Arduino due on: August 21, 2014, 06:33:16 pm
It's for these reasons that on robust systems the freeing and reallocating of RAM is not allowed. Malloc is allowed but only in the setup code.

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Is it possible that I adjust parameters about memory allocation in due?
I would assume so but it would mean delving into the core library code.

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Rob
39  Development / Other Software Development / Re: New peek function for HardwareSerial on: August 21, 2014, 09:09:40 am
I haven't looked at that code for ages but normally to clear a FIFO you just set the head pointer to = the tail pointer and (sometimes) clear a counter.

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Rob
40  Using Arduino / General Electronics / Re: 4 diode rectifier bridge on: August 21, 2014, 08:12:37 am
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every Eagle schematic I see makes my eyes bleed, too many colours, text in the wrong place, etc etc etc.
Amen to that, I think Eagle has an "Obfuscate" option that's on by default smiley

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Rob
41  Community / Gigs and Collaborations / Re: Arduino Development person wanted. on: August 21, 2014, 08:08:17 am
That looks like a heck of a lot of work, are you prepared to spend many $1000s?

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Rob
42  Development / Other Hardware Development / Re: Shield for programming Uno over RS485 signal lines on: August 20, 2014, 05:49:49 pm
It's been a while now and I can't find the schematics, but I think I used an inverted data signal to DE and tied DI low.

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So when the Data was low it would turn off the Driver.
So that scheme would do the reverse, the driver is off for an idle (or otherwise high) UART output.

Also I was just thinking, for low data rates the termination resistor should not be required in the first place. I'm designing something similar right now and the use of a 120R resistor would blow any low power ideas out of the water, so I am thinking of limiting the speed and ditching the termination resistors.

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Rob
43  Using Arduino / Networking, Protocols, and Devices / Re: TX0108 Bi-Directional Voltage Translator Not Working For SPI on: August 20, 2014, 05:16:15 pm
This won't help much and not what you want to hear but I used to think those chips were the answer to all my prayers, but when I used one in a design for SPI it just would not work. I didn't personally do the hardware debug but spent ages on Skype with the guys that did, all to no avail.

It's been a while now but the symptoms you describes sound awfully familiar.

Eventually we gave up and changed the design.

One thing about those chips is that they have a 4k series resistor on the IO, that means they are a very weak driver and of course you can't really use pullup/down resistors but you don't appear to have any.

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Rob
44  Using Arduino / Microcontrollers / Re: Replacing Arduino Due Chip (ATSAM3X8E) on: August 20, 2014, 05:07:17 pm
Removing SMDs is normally a very easy task if you have a hot air station. I have not removed such a large chip I admit but with the right nozzle it should be simple.

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Rob
45  Using Arduino / Networking, Protocols, and Devices / Re: One SPI master(arduino), two slaves(arduinos). Need advice. on: August 20, 2014, 05:04:08 pm
Firstly newSoftSerial has nothing to do with SPI.

If you need to use SPI for > 1 device you have to implement the CS signals for each device yourself, normally this is done with a couple of output pins.

If you just want two or three Arduinos to talk you could used newSoftSerial as well, there are many ways, but I would ask why you think you need multiple Arduinos for what appears to be a simple task.

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Rob
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