Hi everyone,
I’m trying to interface a Schneider Electric / L&T DLMS Category C3 bi-directional energy meter using its RS232 port, which is exposed using an RJ11 4-pin connector. I’m stuck at a few points and would really appreciate guidance.
1. RJ11 RS232 Pinout (4-pin) for L&T / Schneider meter
The meter manual is not clear on the RS232 pinout.
Does anyone know the exact mapping for:
Pin 1 – ?
Pin 2 – ?
Pin 3 – ? (ground?)
Pin 4 – ?
A confirmed TX, RX, GND assignment would help a lot.
2. No voltage on pins?
When I check the RJ11 pins using a multimeter, I don’t see any voltage on any lines.
Is this normal for RS232 ports on DLMS meters until a request frame is sent?
3. Using a RAW MAX3232 IC (14-pin)
I have a bare MAX3232 IC (14-pin DIP), not the breakout module.
Questions:
Which pins do I connect to the RJ11 TX/RX/GND lines?
Which pins go to the ESP32’s UART GPIO?
Where exactly do the charge-pump capacitors (0.1 µF or 1 µF) go?
(C1+, C1–, C2+, C2–, V+ and V– pins confuse me.)
Should MAX3232 be powered from 3.3V or 5V in this setup?
4. Connecting to ESP32
Once the MAX3232 is wired, I plan to connect RS232 → MAX3232 → ESP32 UART.
Any recommended GPIO pins for UART?
Is this the correct UART setting for DLMS meters?
9600 baud, 8E1?
5. Reading DLMS data
If someone has successfully read data from this meter:
Do I need IEC-62056 handshake (/?!) before DLMS?
Do these meters respond directly with DLMS HDLC frames?
Any sample Arduino/ESP32 code would be extremely helpful.
Hi, 1. I can say that you’ll…
Hi,
1. I can say that you’ll save a lot of time if you buy the ready-made cable.
2. You can't measure voltage levels from RS-232 with a multimeter. You need an oscilloscope for that.
4. UART settings depend from the meter and how it's configured.
5. IEC-62056 handshake is needed only when connecting with the optical probe.
Check this:
https://github.com/Gurux/GuruxDLMS.c/tree/master/Arduino_IDE/client
BR,
Mikko