Serial Cable for Modela MDX-20

Making a serial cable for Modela MDX-20 Mini Mill

You might find yourself in a fab lab somewhere with a modela mini mill and a computer - but no out-of-the-box cable which seems to work. This tutorial then is written for you. The modela has a 25 pin female serial output connection, which in this case is output to a 9 pin female connector, which in turn is connected to a Star Tech USB to RS232 Serial Adapter Cable. The Star Tech cable contains a chip which is recognized as a port on a host computer when plugged in to one of the USB slots.

Even though serial printer cables may look alike, they are not created equal - refer to the following links to view the various pinouts available:

This tutorial was developed at Fab Lab Addis. We happened to have a cable with 6 wires which didn't work. It had been cut in half and rewired a couple of times, so was somewhat suspect. Instead of hoping to make it work as it was, we decided to modify according to the following link, which recommends an 8 wire connection:

1, 8 -------- 20
2 --------- 2
3 -------- 3
4 --------- 5, 8
5 -------- 7 GROUND
6 -------- 4
7 -------- 6

The column on the left refers to the pinout for the 9 pin connector, and the column on the right for the 25 pin connector.

Note below that the 9 pin socket is numbered for the female connector, and the 25 pin socket for the male connector. The pinouts are shown below:

We then stripped down the existing cables to reuse the connectors, and then cut a length of 9 wire ribbon cable from the fab lab inventory to make the connections as described above:

We then soldered the wires to the 25 pin connector - note the orange jumper between pins 5 and 8:

We then soldered to the 9 pin connector, which was plugged into the Star Tech USB to Serial connector:

BTW, Don't forget to solder a jumper wire to ground pin 5 on the 9 pin connector, and pin 7 on the 25 pin connector. Ground these pins to the shell housing

We are now ready to configure the modela with a host computer running the fab modules. In this case, we chose a machine running a recent version of Ubuntu. We open a terminal, and enter the following command as "sudo" at the prompt before plugging in the modela cable:

sudo ls dev/tty*

We then plug in the modela cable, and re-enter the above command:

sudo ls dev/tty*

With any luck, you should see a new port appear in the display, which in our case was ttyUSB0. It may be different for you, depending upon what you have plugged into your computer . Assuming you have soldered everything correctly (without any shorts!), you now have a cable which will communicate via the fab modules with your Roland Modela Mini Mill

We now hand you off to an excellent tutorial which describes how to take the port determined above, and configure the fab modules so you can start milling circuit boards:

One note, there have been some additions to the Ubuntu install dependencies since the above tutorial was written. You may see those additions at the following link:

which is just one additional line:

sudo pip install PyOpenGL PyOpenGL_accelerate numpy

Also, as of this writing, the current module dated 7/6/13 has a commit issue that screws up the path - you may use an older version dated 8/16/12 untill that problem is resolved. If I can figure out how to upload a .zip file in D7, I will place it here. Here is a tutorial that might help me when I have some time to kill:

Here are a few more links of interest: (windows configuration) (using Eagle)

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