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?

  • 2
    \$\begingroup\$ Why are you not asking this question in the customer support section for the DG600F on sparkfun. It would seem the most appropriate place to ask. \$\endgroup\$
    – Andy aka
    Oct 3, 2019 at 11:26
  • \$\begingroup\$ Because it does not seems like a problem with the device itself (the device works and sends the signal if used with a special board), but the problem with 12V - 5V FDTI connection to the PC, which can be interesting for other enthusiasts in the future. \$\endgroup\$
    – goooseman
    Oct 3, 2019 at 11:53
  • \$\begingroup\$ And I have the same problem with NV10+ USB from Innovative Technology \$\endgroup\$
    – goooseman
    Oct 3, 2019 at 13:29
  • \$\begingroup\$ Perhaps it is outputting RS232 levels and not logic levels. Your bare USB adapter may now be damaged, and even if not the signal sense is inverted. If so you probably want to buy a USB serial product with a nine pin D connector (modern RS232 tradition) instead. This is why having and reading the specification is key. \$\endgroup\$ Oct 3, 2019 at 13:48
  • \$\begingroup\$ Well the datasheet talks about RS232 which implies positive AND negative signals with levels up to -15V and +15V but the pictures actually show 5V TTL or CMOS signals. So the output signal is NOT RS232 standard. What about the switch configuration? Did you read the datasheet (aka RTFM)? \$\endgroup\$ Oct 3, 2019 at 19:02

1 Answer 1


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.

  • \$\begingroup\$ This is not a meaningful answer. That one device with a 12 power supply was connectable in this way does not in any way mean that another device would be, because what the signal output is may be entirely different between the devices. There are many devices meeting your description which would destroy the CP2102 if connected in the way you propose. Your device might not be one of them - but their existence makes your claim here nonsense. \$\endgroup\$ Oct 4, 2019 at 14:38
  • \$\begingroup\$ Ok, didn't think about this. \$\endgroup\$
    – goooseman
    Oct 7, 2019 at 3:09
  • \$\begingroup\$ By the way the original problem was just a fault device. Found another DG600F for a test and it is working great with the same settings. \$\endgroup\$
    – goooseman
    Oct 7, 2019 at 3:10
  • \$\begingroup\$ Removed the original conclusion from the answer \$\endgroup\$
    – goooseman
    Oct 7, 2019 at 3:11

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