Inspired by Wildebus

[Fisherman]

Cheaper at http://onboardenergydirect.co.uk/shop/ with the Motorhome discount code as found on
https://motorhomer.com/discounts/
If you want to buy new @Fisherman

RAW, I don't even know what its for, its all gobbledygook to me, just trying to be helpful.

 

[RAW]

Personally think all this is better off on the MHB site TBH and all resources can be in one place
Not sure if Phil @Geeky Philip could find a way to sort that out ?

 

[wildebus]

I've just done a little search on Amazon for a USB Cable and I noticed quite a few were labelled with wording like "USB to TTL 3.3V" for example. I wonder if within the USB plug there is some kind of componentry that is more suitable to using with a mismatched voltage requirement? When I tried briefly in the past to make up my own cable, I just used a standard lead I had lying around - a USB-A (The plug that goes into a computer or charger) to USB-micro (phone end) data lead, which has just end to end straight wires, and chopped the end off. Might need "something" else besides?

 

[st3v3]

I'll go with it being the 3.3v isolation

 

[alwaysared]

I did all this myself and never got my MPPT 100/30 and Raspberry Pi 3 to link up with the homemade cable scenario. Pretty sure I tried all the pin-out options at the time and concluded it was likely down to whatever extra components Victron use in their own USB cables
View attachment 81547
So just to confirm you have this working on a raspberry pi (if so which one?) using a homemade cable UART to USB connected to an MPPT controller OR connected to a BMV ? TBH I never tried it on the BMV I have so hoemmade USB to UART may work with the BMV's but not the MPPT controllers ? Thanks @alwaysared , would also be interested in your arduino set-up if you have details of that anywhere.

The answer is yes to everything, I've used a Raspberry Pi 3 Model B+ with a Sandisk Ultra 16Gb micro SD and the cables are homemade, it wasn't about cost (although I made two for less than a tenner) it was more to prove they can work and that the Pi is usable and so far they have and it is

Regards,
Del

 

[alwaysared]

I just used a standard lead I had lying around - a USB-A (The plug that goes into a computer or charger) to USB-micro (phone end) data lead, which has just end to end straight wires, and chopped the end off. Might need "something" else besides?

The cables need to be "USB to UART" which converts the USB to a Comm port because the MPPT and BMV712 are a serial connection not USB.

Regards,
Del

 

[SquirrellCook]

If you wanted the TTL level 5 volts to 3.3 volts couldn't you just divide the voltage with a couple of resistors?

 

[SquirrellCook]

Electrickery involved.

USB to UART circuit

Now a days computers are uses USB ports to interface external peripherals. If we wish to connect a microcontroller with computer or laptop means, we need to convert UART signal…

www.theorycircuit.com

 

[alwaysared]

If you wanted the TTL level 5 volts to 3.3 volts couldn't you just divide the voltage with a couple of resistors?

There's not much use in worrying about the voltages, it's not needed or connected

Regards,
Del

 

[st3v3]

There's not much use in worrying about the voltages, it's not needed or connected

Regards,
Del

What about the voltages on the RX/TX signal lines?

 

[campervanannie]

Del, you lost me at VE Direct but I'm well impressed anyway

I can beat that as soon as he mentioned raspberries I went to the fridge

 

[alwaysared]

What about the voltages on the RX/TX signal lines?

I would assume they are standard serial port connections, which are usually between 0v and 3.3v (but can be 5v) when transmitting/receiving but I believe that the device transmitting data ie. the Victron MPPT will decide on the voltage not the device receiving data ie the Pi. All I know is that they work
I think the confusion is that the USB to UART and standard USB cables have a 5v wire (red) but this is not needed for a serial port and is usually used to power or charge USB devices when needed I've used USB to UART cables for programming security alarms and telephone systems which all need a serial connection and non of them have ever needed the 5v from the USB to UART cable to be connected. if you plug one into a Windows PC or laptop it shows up as a Comm port.
If using homemade leads is a worry then just buy the Victron ones, they're hardly going to break the bank and it's still costs less than a Colour GX Controller

Regards,
Del

 

[wildebus]

Something that might be worth knowing if you haven't tried already ... You can use the connections via a standard USB Hub if you need more connections than the 4 the Pi has (this is also useful if you use the genuine Victron Dongles as those block adjacent USB ports on the RPi, so without a Hub, you are limited to 2 Victron Dongles only).
Also, distance does not seem to be a factor ... the VE.Direct cables come in upto 20 metre lengths, and you can certainly use a USB extension lead if you need to extend (I used a Logitech USB Mouse extension to connect the BMV at the front of the van to the RPi at the rear until I changed from an RPi to a Venus GX).

 

[SquirrellCook]

The only down side of this is that I've just seen on the news that there has been a flock of motorhomes on the road heading to shops. It seems they are running out of pastry and raspberries!

 

[alwaysared]

Something that might be worth knowing if you haven't tried already ... You can use the connections via a standard USB Hub if you need more connections than the 4 the Pi has (this is also useful if you use the genuine Victron Dongles as those block adjacent USB ports on the RPi, so without a Hub, you are limited to 2 Victron Dongles only).
Also, distance does not seem to be a factor ... the VE.Direct cables come in upto 20 metre lengths, and you can certainly use a USB extension lead if you need to extend (I used a Logitech USB Mouse extension to connect the BMV at the front of the van to the RPi at the rear until I changed from an RPi to a Venus GX).

Yes I had to use a couple of extension leads, they do need to be good quality ones though, one from Poundland didn't work but a Ugreen one was fine
Maximum Serial Cable Length I have some USB over Cat5 adapters, I wonder if these would increase the length if needed?

Kind regards,
Del

 

[st3v3]

While we are on the subject of Victron cables, I needed to extend the Pi to MPPT cable. Cut and soldered in a bit of cat5 cable, works fine

 

[st3v3]

I'm just hoping for someone to write the code in to the Pi so that you can hook temperature sensors up to it and have it graphed in VRM...

 

[alwaysared]

I'm just hoping for someone to write the code in to the Pi so that you can hook temperature sensors up to it and have it graphed in VRM...

Yes that would be nice

Regards,
Del

 

[wildebus]

I'm just hoping for someone to write the code in to the Pi so that you can hook temperature sensors up to it and have it graphed in VRM...

I cannot deny ... this is one of the reasons I decided to change to a Venus GX ...

And you can set an alarm if a temp goes above or below a chosen temp (so warning you if say the room temp dropped to a level you could have water freezing for example)

 

[Okta]

I have to say I am impressed by this discussion and the various skills of others. I do not have such skills but I do like to be able to monitor things remotely. I have a Victron BMV 700 battery monitor with a bluetooth dongle which allows me to monitor it when I am near by. Does anyone know of a method that an electronics numpty could use to monitor this device remotely using the mobile phone network? Obviously this would be more expensive than the clever diy solutions but during this lockdown I have realised being able to keep an eye on what my toys are doing would be useful.
Any ideas?