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How to Set Up a CAS Scale with the Sunmi POS

Connect a CAS scale to the Sunmi POS with a USB-to-serial cable, then set the scale to continuous mode so Cents can read weights.

Written by Euri

This guide covers connecting a CAS scale to your Sunmi POS with a USB-to-serial cable, then setting the scale to continuous mode so Cents can read the weight. The two short clips below show the cable connection, and the steps that follow walk through the scale settings.


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Watch: connect the cable

These two short clips show how the cables connect. There is no audio.

Part 1

Part 2

What you'll need

  • A CAS scale (for example, a CAS BW or PW model) with its existing serial cable, which ends in a grey connector.

  • A USB-to-serial (RS-232) cable with an FTDI chipset. One cable confirmed to work is the OIKWAN USB-to-RS232 DB9 (FTDI, 10 ft).

  • Your Sunmi POS.

Connect the CAS scale to the Sunmi

  1. Find the scale's existing serial cable. On a CAS scale it plugs into the special connector on the back of the scale and ends in a grey serial (DB9) connector.

  2. Join that grey serial connector to the matching end of the USB-to-serial cable. The two serial heads connect together.

  3. Plug the USB end of the cable into the USB port on the side of the Sunmi.

The two clips above show each connection.

Set the CAS scale to continuous mode

For Cents to read weights, the CAS scale needs to be in continuous send mode (U-Snd).

  1. Make sure the scale power is OFF. While holding the ZERO key, press the power key. The display shows "U Set".

  2. Press the ZERO key until you see one of these: "noSnd", "K-Send", "S-Send", "U-Snd", or "C-Send". Your current setting may be any of these.

  3. Press the TARE key until the display reads "U-Snd".

  4. Press the ZERO key to set the mode to "U-Snd".

  5. Press the ZERO key until the display returns to normal. Other settings appear along the way; just keep pressing ZERO, as they do not matter here.

  6. To confirm, place something on the scale. You should NOT hear a beep when the weight stabilizes. The "O" in the top left of the display shows when the weight is stable.

  7. If the scale beeps, turn it off and go through the steps again, following them carefully.

Troubleshooting

  • Cents isn't showing a weight? Recheck the cable: the grey serial connector fully seated into the USB-to-serial cable, and the USB end firmly in the Sunmi. Then confirm the scale is in U-Snd mode.

  • The scale beeps when the weight settles? It is not in continuous mode yet. Turn it off and redo the continuous-mode steps.

  • Not sure your cable is right? It must be a USB-to-serial (RS-232) cable with an FTDI chipset that connects to the scale's grey serial head.

Need assistance?

Feel free to text our Cents Support team at 888-302-8809.

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