I'm using Astroberry running on a Raspberry Pi to control my HEQ5 pro mount. I access this via Wifi from my MacBook pro running Kstars. It will work one time, then the next I get a Serial read error and nothing happens. In fact the serial read error has turned persistent.
My mount is connected to the Raspberry Pi via the handset and a RS232 to Usb converter using the Prolific chipset. I'm suspecting the cable may be dodgy so am considering purchasing an EQDir cable from First Light Optics and they have advised me that :
The FTDI chip should automtically install in Astroberry and show up as a serial device. You shouldn't need any additional drivers for this but you will then need EQMOD software which Astroberry should already have installed to control the mount.
Looking on EKOS I can see an EQMOD mount is listed so am assuming the EQMOD software referred to by First light optics is installed. So would I be right in assuming that I connect the mount to the Raspberry Pi and then choose the EQMOD mount in EKOS instead of the Synscan mount to enable connection?
Apologies for what might be an obvious question but I thought it worth checking first.

This is correct. You just need to connect the mount directly with Rpi. Any USB-serial converter will do. Just make sure it is 5V compatible.

He actually needs an EQMOD cable rather than a serial to USB converter and not use the handset at all, but skywatcher mounts do vary in there EQMOD cables, some mounts require 5v and some only 3.3v, I think the EQ6 is only 3.3v...it’s a different EQMOD cable to many of the other mounts because of this and the fact it’s a different Plug on the mount...

Call it whatever you like. Skywatcher interface is technically UART TTL, which is serial interface.
Just take a look at this link eq-mod.sourceforge.net/eqdirect2.htm
You can connect it directly to another serial device and that's all you can do. You cannot connect it to USB. If you want to connect it to USB you need serial to USB converter, which supports UART TTL voltage level.
I don't thing the TTL voltage level varies between Skywatcher mounts. At least you're wrong regarding EQ6, which I use personally. It is TTL 5V. The same for EQ5 and EQ8.
The only difference is the plug on the mounts that is different - either RJ11/45 or DB9.

Could you give me a specific case of other TTL voltages and plugs other than mentioned above. Sources supporting these would be just great.

Hello,
The only reason I said that the voltages did vary on skywatcher mounts, is that when I bought my EQ8 I got In touch with the guy that runs Dew Control (www.dewcontrol.com/) here in the U.K. who made and sold me my EQMOD cable for my EQ6 Mount, and asked if I could just swap the plug on the end to match my new mount, he told me no, as the voltages are different, one is 3.3v and one was 5v, he went on to explain the electronic reason why, but it went over my head...
So if he was wrong then I apologise...

No need for apologies whatsoever It's all about security of our hardware, because using inappropriate signaling voltage might be destructive for mounts' controller board.
For clarification and making sure that we are on the safe side I have just reviewed tech specs of Skywatcher mounts. The conclusion is:

- EQ6(Pro) and (H)EQ5 - expect to see a minimum 4V active high signal, lower signaling voltages will not work - use TTL-232R-5V cable/converter for these mounts
- AZEQ6GT, EQ8 - have a 5V tolerant 3.3V signaling interface, so both 3.3V and 5V active high signal will work - use either TTL-232R-5V or TTL-232R-3V3 cable/converter for these mounts

Take a look at example cables and converters using FTDI chip here: www.ftdichip.com/Products/Cables/USBTTLSerial.htm

I personally love ready to use USB cable with build-in converter like the one on the image below. You just need to finish it up with a plug matching your mount.

Ok, so that’s where the 3.3v and 5v comes from, so I was given wrong info, which is annoying as I bought a new EQMOD cable based on that info, when all I needed to do was swap the DB9 for a rj45... on the cable I already had...

This is the reply I got from the guy at Dew control...

Hi, you are correct, it's all down to the voltage levels of the signals. The HEQ5 and EQ8 require TTL voltages (5v), whereas the EQ6/NEQ6 seems to get away with 3.3v. So level shifters are required or a cable with TTL level outputs.

This is totally incorrect.
As I already stated in this thread EQ6 TTL voltage is 5V not 3.3V! I do own it and I do use it, really, with 5V TTL USB - serial converter. It's ! EQ8 uses 3.3V (you own it right? what cable/converter do you use? is it 5V?) BUT it accepts 5V on RX input. This means it DOES NOT transmit 5V TTL levels on TX output. No level shifters are required for any mount as far as you use proper FTDI converter /cable - 3.3V OR 5V. If you use a converter/cable which does not much your mount's TTL levels you HAVE TO use level shifters. But why would you use such a converter/cable?

Please let's keep it clear and transparent. Otherwise ppl will ruin their mounts with inaccurate information on voltages.

Hold on,
I am only Sharing the reply I got from the guy who runs Dew control, I am not stating this is fact, so please don’t say that I am giving wrong info....you asked, so I shared...it’s not my info but what was given to me ...right or wrong....

I've seen the discussion... and I was apologising for asking an obvious question!!! Perhaps it was a good job I asked. Anyway I've been away from the forum for a couple of days refurbishing some old 'scopes for the astro society.

There has been much said especially about voltage levels. I think though have managed to pick up that the HEQ5pro I have is a 5v system. So I will select the cable accordingly.

Thanks for an interesting couple of leads in the discussion as well.

Regards

I believe the HEQ5 is expecting 4V+ signals, so 5V will work. But I can also say I have a homemade bluetooth interface based on the HC-05 bluetooth serial adapter that worked fine at 3.3V without level shifting. Although as a precaution my final module did include a small level shifting circuit board.