EQMOD can't connect: Skywatcher EQ5 Synscan

[Serhii Solohub]

3 hours ago, malc-c said:

The wiring of an EQDIR connector is different from a standard USB to serial adaptor.  True RS232 also operates at +/- 12v rather than 0-5v TTL levels, so even if you do wire up the pins as per the EQMOD website you end up shoving 12v or more into the PIC microcontroller and it blows. That's why I gave you the manufactures part number from the FTDI website.

malc-c, thnx for the info ! Do I understand right: in the FTDI USB-TTL converter the voltage of RX and TX is 0V (as logical 0) and 5V (as logical 1), and in the cheap USB-TTL converter voltage of RX and TX is -12V (as logical 0) and +12V (as logical 1) ?
That sounds a little bit strange, and I just want to understand this fully... I see a lot of USB-TTL converters like i.e. https://aliexpress.ru/item/1875954176.html , so they may have -12V and +12V at RXD and TXD pins ?

You see, I have made my own mount controller based on Arduino, as so as my friend has built his own one. But his controller has no any control from PC except several Serial port commands to sync current RA/DEC position and a GOTO-command and ST-4 guiding. Mine has the same functionality + I have made a tiny ASCOM-driver for it, so ASCOM PulseGuiding is present too. Now he wants to create a new version of his controller with full EQMOD support (what means: a full support of Synta SynScan protocol). And I helps him with the understanding of that protocol.

Another my friend has bought EQDRIVE mount controller as a replacement of the stock SynScan mount controller (aka "motor board") because EQDRIVE has belt gear in stock. So I bought from him the unnecessary SynScan EQ5 mount controller (photos in attachment). It should be fully workable except of the connector that was moved to EQDRIVE to make it possible to connect EQDRIVE with motors using the stock wires. Does not matter, all I need of this is to connect it to the PC with EQMOD and see the COM port traffic to compare it with my Arduino SynScan "implementation" (such a load word 🙂 ) .

I have described this to make it clear why am I trying to understand the EQDirect's peculiar properties: that is not a problem to obtain FTDI cable (except the delivery time to Ukraine), but as a person who want to work with the SynScan protocol I really want to understand the details of how EQDirect works and why cannot I use a simple USB-TTL like the one that Arduino has on its board. And I don't know the better place to ask cause on Arduino forums nobody knows anything about SynScan motor boards. So sorry for sucj a lot of questions about all of that USB-TTL's... But I really want to understand.

 

[malc-c]

22 minutes ago, Serhii Solohub said:

malc-c, thnx for the info ! Do I understand right: in the FTDI USB-TTL converter the voltage of RX and TX is 0V (as logical 0) and 5V (as logical 1), and in the cheap USB-TTL converter voltage of RX and TX is -12V (as logical 0) and +12V (as logical 1) ?
That sounds a little bit strange, and I just want to understand this fully... I see a lot of USB-TTL converters like i.e. https://aliexpress.ru/item/1875954176.html , so they may have -12V and +12V at RXD and TXD pins ?

The clue is in the description 

Quote

TTL based USB to RS232 module provides the best and convenient way to connect RS232 TTL devices 

This is not the true definition, but RS232 is a protocol.  That means that how data is transmitted and received in terms of the 1's and 0s by pulse widths etc is the standard.  Initially when serial was used between two devices the data was sent over log distances and operated at +/- 12v due to the distances.  When it was required to interface to devices that ran at 5v and the TTL logic levels were established you had to use MAX232 chips and four capacitors as charge pumps to take the 5v TTL serial data and translate that to true RS232 +/- 12v levels  (and  vice-versa at the other end if the other device used 5v TTL chips).  Then along came USB.  A true "standard" USB to serial  converter does a similar thing.  They basically take the 5V TTL level USB serial protocol convert it to RS232 serial, and then raise the voltages in the same way as the MAX232 chips to output at true standard.   Then the RS232-5VTTL standard was developed and this done away with the voltage leveller, so now the chipset in the adapter simply took the USB protocol and converted it to RS232 protocol, but the voltages remains the same at 5v.  The only disadvantage was distance, but then most of these were for use over 2-3 metres so that wasn't a problem. 

Most devices these days are RS232-TTL convertors, but you can still get standard RS232 convertors - hence my comment.

Regards to the FTDI and other devices.  FTDI devices work well with Skywatcher mounts.  You'll notice that the supported operating systems listed in the webpage you linked to lists every operating system up to and including Windows 7.   In 2012 when Windows 10 was in development MS opted to completely rewrite the kernal, the core of windows, and as such a lot of legacy drivers would not work and new drivers needed to be written by 3rd party vendors.  Prolific had developed the PC230x series of USB to 232TTL chipset and didn't want to invest in news drivers so since 2012 has technically not been supported un windows 10.  (In fact that device doesn't even have windows 8 support, and requires a late build of windows 7 to work).  However in recent years legacy drivers have appeared for the 230x chipsets and whilst windows 7 drivers can be made to function on windows 10 it's often hit and miss.  If I had £1 for every post I see on forums and user groups where people are experience problems communicating to a SW mount using a prolific chipset I could retire tomorrow    - The strange thing is that in some of the recent  versions of handsets, and some mounts with USB ports, SW have used prolific chipsets in them, like a built in EQDIR cable ! 

For the past 10 years I've had a home made EQDIR cable which is basically a 2m FTDI- 2325V ready made cable with an RJ45 connector crimped in to the RX/TX and GND wires as per the  diagram on EQMOD's website - It's worked without issue for the whole time.  Yes it costs a little more initially, but it last and it works.  FTDI produce up-to-date drivers, and they are windows 10 compliant.

Hope that helps....

[Serhii Solohub]

5 hours ago, malc-c said:

The clue is in the description 

This is not the true definition, but RS232 is a protocol.  That means that how data is transmitted and received in terms of the 1's and 0s by pulse widths etc is the standard.  Initially when serial was used between two devices the data was sent over log distances and operated at +/- 12v due to the distances.  When it was required to interface to devices that ran at 5v and the TTL logic levels were established you had to use MAX232 chips and four capacitors as charge pumps to take the 5v TTL serial data and translate that to true RS232 +/- 12v levels  (and  vice-versa at the other end if the other device used 5v TTL chips).  Then along came USB.  A true "standard" USB to serial  converter does a similar thing.  They basically take the 5V TTL level USB serial protocol convert it to RS232 serial, and then raise the voltages in the same way as the MAX232 chips to output at true standard.   Then the RS232-5VTTL standard was developed and this done away with the voltage leveller, so now the chipset in the adapter simply took the USB protocol and converted it to RS232 protocol, but the voltages remains the same at 5v.  The only disadvantage was distance, but then most of these were for use over 2-3 metres so that wasn't a problem. 

Most devices these days are RS232-TTL convertors, but you can still get standard RS232 convertors - hence my comment.

Regards to the FTDI and other devices.  FTDI devices work well with Skywatcher mounts.  You'll notice that the supported operating systems listed in the webpage you linked to lists every operating system up to and including Windows 7.   In 2012 when Windows 10 was in development MS opted to completely rewrite the kernal, the core of windows, and as such a lot of legacy drivers would not work and new drivers needed to be written by 3rd party vendors.  Prolific had developed the PC230x series of USB to 232TTL chipset and didn't want to invest in news drivers so since 2012 has technically not been supported un windows 10.  (In fact that device doesn't even have windows 8 support, and requires a late build of windows 7 to work).  However in recent years legacy drivers have appeared for the 230x chipsets and whilst windows 7 drivers can be made to function on windows 10 it's often hit and miss.  If I had £1 for every post I see on forums and user groups where people are experience problems communicating to a SW mount using a prolific chipset I could retire tomorrow    - The strange thing is that in some of the recent  versions of handsets, and some mounts with USB ports, SW have used prolific chipsets in them, like a built in EQDIR cable ! 

For the past 10 years I've had a home made EQDIR cable which is basically a 2m FTDI- 2325V ready made cable with an RJ45 connector crimped in to the RX/TX and GND wires as per the  diagram on EQMOD's website - It's worked without issue for the whole time.  Yes it costs a little more initially, but it last and it works.  FTDI produce up-to-date drivers, and they are windows 10 compliant.

Hope that helps....

Thnx Malcolm ! So, as I understand, the USB-TTL converter I mentioned above SHOULD not harm the motor board, but it's possible to have troubles in communications between the PC and the motor controller when I use this cheap chip 🙂 . Also, I may experience a troubles in Windows 10 due to lack of official drivers. I think I will measure the voltage of RXD and TXD pins and, if it it near the 5V, I [maybe] will try cause I have this converter at home. But I think I will order the FTDI EQDirect cable. Anyway, later I'm going either to use that board controller with the second mount or to sell it to someone with the good, 100% worlable cable in pair 🙂 .

[malc-c]

Yes, basically that adapter should be compatible with the TTL 5v logic levels that the motorboard is expecting, but officially there is no driver support for Windows 8 or 10, and whilst drivers form Prolific and other 3rd party sites are available there is no guarantee that they won't play up.  Nearly every post on the EQMOD user group about missing comports, or EQMOD timing out are related to people using Prolific 230x based cables.  Personally, I would just order an EQDIR cable from FLO and then you don't have to worry about things...

[Geoff_L]

On 29/04/2021 at 17:10, Serhii Solohub said:

Hello. So, do you need to use the handset control as intermediate dedice between PC with EQMOD and SynScan EQ5 mount controller device ?

I'm responding here just for clarity as others have given much better info than I can. Back in 2017, I'd only just acquired my EQ5 Pro mount and didn't understand that there are two types of 'direct' cable. The one I have is a serial cable that plugs into the dedicated port at the bottom of the handset. However, there is another type (that I haven't tried) that plugs into the control box in place of the handset.  So richyrich_one and I were actually talking about two, different cables.