Category:Mesa Interface

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Card selection

The cards selected for this wiki are the combination of a 5i25 + 7i77. The 7i77 was chosen because it provides analog output - that is compatible with the Argon servo drive used, encoder input (controller will receive the encoder feedback) and several IO, that are enough for the total project. Its price is also low. The 5i25 was chosen because the PC motherboard have a PCI slot and it provides two outputs for DB25 type of cards, that includes the 7i77. We also used a 7i75 attached to the second port available on the 5i25 because it can drive a step direction servo (not analog) that will be used for a non critical axis that provides secondary operations. This set up is not covered on this wiki, but with a simple 5i25 we can directly use a 7i77 (six analog servos, with several IOs) and another DB25 card, in this case a 7i75.


5i25 firmware.JPG

Since 7i77 daughter board will be used, the 5i25 FPGA board will need the correct firmware. In this case, 7i77 firmware. The firmware of this board can be changed if needed using the mesa flash utility, please see page 12 of manual . The different firmwares can be found on mesa 5i25 support software

Download the firmware folder from mesa 5i25 support software, extract it and go to the folder where the *.bit and *.pin files are located (../Downloads/5i25/configs/hostmot2).

Now verify it the board have the desired firmware. In this case we need the 5i25+5i77+7i78 firmware.

run the following command:


The firmware on the mesa 5i25 isn't the wanted, so we will flash witb the correct one by runing the command:


Now the new firmware is flashed. It can be checked running "--verify":


Jumper Selection

Before power the mesa cards for the fist time, its crucial a proper setting of the jumpers on the boards. Bad jumper selections can damage the mesa cards.

It will be an external 5VDC power supply, so the option to supply 5V power from the host computer to the breakout board will be disabled.



  • W1 - down
  • W2 - down

These 2 jumpers on the down position disable the supply of 5VDC from Mesa 5i25 to the dougther boards on the tow ports (W1 for port P2 and W2 for port P3)



  • W1 - left
  • W5 - right

The isolated field I/O on the 7I77 runs from a switching power supply that can be powered by field power or a separate supply (VIN) with ground common with field power. W1 on the left hand position jumper determines that comes from the field power (typical situation )

W5 on the right determines that the logic power comes from an external 5VDC power supply instead of the 5i25 FPGA board.



  • W1 - down

W1 on the down position determines that the logic power comes from an external 5VDC power supply instead of the 5i25 FPGA board.


Logic Power

Why external 5VDC power supply

A external 5VDC power supply was chosen as Mesa daughter cards share his logic power with external devices. For example analog output, encoder, and RS-422 interface like Mesa on 7i77. Some encoder models can use a considerable amount of current, so to keep the PCI bus of mesa 5i25 without any kind of heavy load and to not make any compromise in the future due lack of power, an external 5VDC power supply is desirable.


7i77 logic power.JPG

As described on the Mesa 7i77 manual, the logic power supply is made by the TB1 connector.


7i75 logic power.JPG

Its the same for the 7i75 board, please see the Mesa 7i75 manual.

Field Power


7i77 field power.JPG

The 7I77 has a 32 input, 16 output isolated field I/O system to support a wide range of input and output devices. The isolated I/O is intended for low voltage DC control systems (commonly 24VDC). Inputs are sinking type. That is they sense positive input voltages relative to field ground. Output are sourcing type, that is they supply field power to field ground referred loads. [1]

Its need to provide a power source to the TB2 connector on the Mesa 7i77 board. TB2 pinout can be found in the Mesa 7i77 manual


After a correct jumper selection and provide field and logic power to the daugther boards its time to connect them to the Mesa 5i25 FPGA board, using the DB25M IEEE 1284 compliant parallel port cable. the P2 port of the 5i25 is used to connect 7i77 board and the P3 port for the 7i75 board.

7i75 overview.JPG

7i77 overview.JPG

After turn on the power:

7i75 7i77 overview powered.JPG

Mesa 7i77 connections

For the propose of a minimal configuration for one axis, this is the scheme of this board:

Mesa7i77 connections.jpeg


  • Encoder A+ B+ channels
  • Emergency stop button
  • X- limit switch
  • X+ limit switch
  • Drive ready status
  • Drive fault status


  • Analog setpoint
  • Drive enable
  • Drive clear fault


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