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Old 07-07-2019, 03:44 PM
RussellH
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Building an EQDirect cable from ftdi break out board

So Iím wanting to build an EQDirect cable to run Stellarmate from a Raspberry Pi to a HEQ5.

Trying to source the 5v ftdi cable is either difficult (mostly 3.3v versions on ebay) or expensive $15-$50 for 5v version.

I found these arduino breakout boards for the IC version of the ftdi controller https://rover.ebay.com/rover/0/0/0?m...2F192627116019. I may even possibly have some at home already in some of my arduino mega kit gear.

Is there some reason these couldnít be used instead of the expensive cable versions.

Thanks. Russell.
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Old 07-07-2019, 08:39 PM
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mswhin63 (Malcolm)
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Shouldn't be a problem, need to make sure you get the TTL version. Others will not work. I have made a few in my time, including a Bluetooth version. They can be cheap but need to beware of some tutorials. I noticed on the EQMOD page that the modules are powered without decoupling capacitors that could cause some issues.
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Old 08-07-2019, 04:48 AM
RussellH
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Thanks for the info.

This is the specific unit I was thinking of.https://rover.ebay.com/rover/0/0/0?m...2F183565646696

I’m an electronics tinkerer, not an expert, so a bit unsure about the decoupler concerns. Wouldn’t a decoupler normally go between Vcc and Gnd? Vcc isn’t active on EQDirect cable, so what noise suppression is required? How exactly have you handled this?

Thanks. Russell.

Last edited by RussellH; 08-07-2019 at 07:47 AM.
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Old 09-07-2019, 12:30 AM
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mswhin63 (Malcolm)
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Decoupling is to prevent potential instability in a linear regulator. Personally, all my project use Switching regulators that have higher efficiency, especially useful for battery-powered applications.

Decoupling capacitors are placed on both the input and output.

Ripple is another factor but is in most cases covered in the power supply or the battery.

The best thing is to look at the datasheet as a way of verifying the decoupling requirements.

I am moving to Adelaide next week, and so I will not be looking at posts shortly so get your questions in. I don't have the time at the moment to look at datasheets, only provide general information until I move.
Top it off I will be reviewing a Bluetooth Mesh development system for IoT and will be busy with that for a while.

Cheers


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Originally Posted by RussellH View Post
Thanks for the info.

This is the specific unit I was thinking of.https://rover.ebay.com/rover/0/0/0?m...2F183565646696

I’m an electronics tinkerer, not an expert, so a bit unsure about the decoupler concerns. Wouldn’t a decoupler normally go between Vcc and Gnd? Vcc isn’t active on EQDirect cable, so what noise suppression is required? How exactly have you handled this?

Thanks. Russell.
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Old 09-07-2019, 10:40 AM
RussellH
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Alright, I'll just have to wing it for now. I see a couple people have even been running the 3.3v chips on short cables without problems, so I guess it depends on your tolerance for glitches and frying your circuitry. Will be a couple weeks before I can get into building anything anyway.

Russell.
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Old 01-10-2019, 02:01 PM
sj777 (Dave)
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How did you go RussellH? I've just bought an NEQ6 and I'm looking at doing the same thing.



I have heaps of arduinos with on board FTDI USB-Serial interfaces so I followed a few tutorials on deactivating the ATMega chip to allow use o fthe TX and RX pins. Thus far I can't get EQMOD to connect to the mount



I've put my sillyscope on and verified it is TTL level serial comms. I've double checked the RX TX is wired correctly to the DB9 male connector which goes to the mount.



Looking for any help I can get
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Old 01-10-2019, 02:38 PM
RussellH
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Surprisingly, it turned out to be a piece of cake, although I never addressed the decoupling question, but I haven't had any problems yet.

I just got one of the basic FTDI boards from eBay, cut up an old ethernet cable, and soldered on the appropriate wires to the appropriate PCB connections, and mounted it all in two milk bottle lids hot-glued together (see picture).

This was only supposed to be a temporary arrangement while I build a wifi version, but it's been working so well, I haven't even bothered with the wifi one, even though I purchased all the parts.

Not bad for a $3 build
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Old 01-10-2019, 02:56 PM
sj777 (Dave)
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Nice work. I'll keep pluggin away at the problem. My problem may be the zero and one levels are inverted.
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