| Electronics > Projects, Designs, and Technical Stuff |
| USB to serial converter termination |
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| drummerdimitri:
I just received this USB to Serial converter cable: https://www.aliexpress.com/item/4000570382636.html?spm=a2g0s.12269583.0.0.390f2b8bk7eW2b which is plug and play so windows automatically downloads the driver for it but when I try to plug it into my Meanwell TN-1500 inverter via a RJ11 connection and make sure the hardware and software are using the same COM port and BAUD rate, I get a "Inverter not found" error message. I cut the end off the cable thinking the original cables pin configuration may be wrong for my inverter and there are three conductors inside (black white and green) but since I don't have the pin-out, I cannot follow the manual (see attached manual, page 3) to crimp a new RJ11 connector with the correct wire arrangement. Does anyone have a clue what conductors correspond to the correct pins from 1-6 on an RJ11? |
| MarkF:
Paragraph #2 in your linked document gives you the pinout. You may need to swap TXD and RXD? With a meter you can find what color is ground and guess at the other two colors. |
| Ian.M:
Diagram A in the manual you attached shows the relationship between the RJ11 pinout and the standard DE-9 PC COM port pinout. To identify the wires: The ground wire should have continuity back to ground on the USB connector, and if you plug the cable into a PC and open the port in a terminal program, with no data being sent, one of the remaining wires will be a floating input (RxD) which will measure close to 0V and the other (TxD) will output a voltage: +5v or +3.3V if its a logic level (aka: 'TTL') USB serial adapter, and negative -5V to -25V (but unlikely to be more than -9V) for a true RS-232 levels USB serial adapter. See http://tldp.org/HOWTO/Serial-HOWTO-19.html The two types of adapter aren't compatible, your inverter expects true RS-232 levels and, as its only got three wires, almost certainly doesn't provide USB Vbus so you cant use a MAX3232 serial level converter chip, so if you measure a positive voltage with the port open, you'll need to get a different adapter (preferably one with a DE-9 plug as they almost invariably use RS-232 levels). |
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