Electrical – Connect to a serial output device with 12V power input with 5V USB-TO-UART

cp2102ftdirs232sparkfunuart

I have

I need

to connect DG600F to PC by serial cable.

In the Support tips section (in the bottom) of the DG600F product page there is the following connection scheme:

Official DG600F connection scheme

So I've connected by the following scheme:

My connection

  • Red is 12V from power adapter. Connected straight to the device.
  • Orange is ground from power adapter. Connected to ground from CP2102.
  • Black is ground from CP2102. Connected to the device.
  • Yellow is RX from CP2102. Connected to the device.

The ground connection looks like this:
Connection of grounds

What do I expect?

I put an icon into DG600F. The red diode near RX line on CP2102 should light up. I should receive some bytes on my computer using a serial port terminal. (I use serialport-terminal from npm)

What happens

The RX diode lights up, when coin is inserted, but it lights up 5 times less brightly, then it should. It looks like it detects the signal, but it is too low. There is no input in the terminal at all.

What did I try?

  1. I've tried to touch RX line with my finger. There is some random input in the terminal. So CP2102 works correctly.
  2. In the original manual, they've used FDTI cable. So I've bought exactly the same, but the problem is the same: there is no input in the terminal. FDTI does not have any diodes, so I can not tell if it receives the signal.
  3. I've connected DG600F to some cheap Chinese board I have, which outputs 12V to DG600F and connects to the computer through USB as an HID. Through it everything works: coin insert is detected and the board sends the signal to PC. So I can tell, that the device itself works correctly. But I need to work with DG600F directly from the PC, because I have another payment device, which requires the same installation scheme.
  4. I've checked the output from 12V and ground on all connections with a multimeter. The device gets 12.26-12.27V.
  5. I have tried to connect RX with TX on CP2102 connectors and send a signal from terminal. It returned back. This way I can know, that the chip itself is still working.

Any ideas?

I am a software developer, not a specialist in electronics. So what I want to understand: what can be done wrong in this simple scheme:

Official DG600F connection scheme

And why I get the signal, but the diode is very dim?

Best Answer

I understood that this is not an issue with the connection scheme, but the problem with DG600F itself.

It is just a fault device. Found another DG600F for a test and it is working great with the same settings.

And I finally managed to connect to NV10 USB+ device using the same connection with CP2102 (but with an addition of TX channel). And I've used SSP protocol, which works through a serial port.

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