David, that scale have 4 types of protocol (Cause is weight only mode(WO)).
I recommend you to use Elpsa for WO mode. From the manual:
The spanish competitor Epelsa has developed a protocol for the communication between checkout scales [ only-weight scales ] and POS [ or PC ] which has become kind of standard in the spanish market for this type of connections, thereof our interest that our only-weight scales become compatible.
You may use 9600 Baud, 8 databits, stop bits 1, partity even. You can change this, but with default scale configuration those are the best. (If you want to use others, you should change the scale configuration)
To use this protocol use this box:
So to receive the weight you should send a '$' char