4-20mA Comunications

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MaxHeadRoom

Joined Jul 18, 2013
23,639
They are NOT 4-20 mA loop interface.
It sounds 'similar' to Modbus protocol. You must get the full data communication protocol from Gilbarco if you want to interface to some yet as unknown microcontroller.
+1, sounds like Modbus style me also, 4-20ma does not contain digital data, it is a linear/analogue signal communication.
Max.
 
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kubeek

Joined Sep 20, 2005
5,758
Wow, one of the most horrid schematics I have ever seen.
Seriously though, if you got the end devices why not take one apart and trace the communication path to find out what exactly it is and how it works, and then do it similarly? Like the others, I doubt that it is using 4-20mA signals to do digital communication.
 

faley

Joined Aug 30, 2014
88
Sorry Diego. I didn't realize the thread stalled. We really need the pump model number to give you the best info. Basically, Gilbarco uses a proprietary module (PAM- "Pump Access Module") to convert the signal to a RS-232 or RS-485 protocol (I believe there is also a 422a protocol as well). The module interfaces the pumps with a POS ("Point of Sale") system- that's probably your micro-controller. Without the module nothing will work, nothing legal anyway. Hope this helps.
 
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faley

Joined Aug 30, 2014
88
Sorry Diego, regarding the scope, I think you have me confused with BR-549. Per your posting of the manual's info, the pump transmits a digital pulse train. You would need the "key" to decode it- which is proprietary. I've attached a Veeder-Root/Gilbarco system that will give you an idea of what you're "up against" so to speak. (Page 2 has a typical layout.) I take it you have the PAM (site controller)? Do you have all the required components?
 

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Diego Bonilla

Joined Sep 18, 2014
35
Hi Faley

that's what I want to replace(PAM) because it is too expensive, I have the decoding key(The Protocol, every byte and bitword and speeds), my question is how I connect to the dispenser, the need to capture the pulse train hardware.
 

faley

Joined Aug 30, 2014
88
Unfortunately, you need the PAM. I know. It's expensive. The "key" I mentioned was a reference to the hardware and firmware configuration. I really can't help you get around it. I've signed far too many confidentiality (proprietary) agreements to successfully plead ignorance in a courtroom. I do wish you much luck. e-Bay?
 

cmartinez

Joined Jan 17, 2007
7,420
Hi Diego, this seems like my area of expertise.

What you're talking about is clearly a serial protocol. I doubt it's MODBUS from what I've seen so far in this thread, but then again, it could be.
What's the UART signal level? is it TTL or RS232? Or can you configure it for both?
You mentioned that it was 11 bits long, what else does the manual say about that? Start bit, stop bit, etc? Can you provide us with a link to the manual?
Maybe it's as simple as connecting it to your computer's serial port and using the terminal found in every Windows OS to communicate with it... But I'd have to take a look at the manual first.
 

Thread Starter

Diego Bonilla

Joined Sep 18, 2014
35
Hi Diego, this seems like my area of expertise.

What you're talking about is clearly a serial protocol. I doubt it's MODBUS from what I've seen so far in this thread, but then again, it could be.
What's the UART signal level? is it TTL or RS232? Or can you configure it for both?
You mentioned that it was 11 bits long, what else does the manual say about that? Start bit, stop bit, etc? Can you provide us with a link to the manual?
Maybe it's as simple as connecting it to your computer's serial port and using the terminal found in every Windows OS to communicate with it... But I'd have to take a look at the manual first.
 

Thread Starter

Diego Bonilla

Joined Sep 18, 2014
35
Hola cmartinez

como veo hablas mi idioma

si lo que dice alli esta en el manual

lastimosamente solo tengo el manual del protocolo, o sea de como interpretar la señal, pero no se que hardware utilizar, e visto algunos circuitos fisicamente que usan optoacopladores para interfazar y unos inversores, pero aun no estoy claro, ademas creo que la opcion de usar optoacopladores es algo tediosa ya que por la corriente se pueden estar quemando. Lei por ahi en otro foro algo de redes de proteccion, pero creeme que no se mucho de eso.

dame tu correo yo te envio la parte del manual donde habla de la comunicacion.
 

mivan

Joined Aug 5, 2015
1
Hello Diego;

I know its been a while of this post; do you think its possible to have a copy of the protocol document?
Have a software simulator to program and that would be a great help.

Thank you
 
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