Evaluate Retired Melzi Board for XY Stage

In an effort to put a salvaged industrial XY table back to work, the Arduino AccelStepper was used as a quick test to see if the motors and controllers still respond to input signals. Things moved, which is a good sign, but the high precision of the Parker ZETA4 controller demanded step pulses at a far higher frequency than what AccelStepper could deliver.

The search then moved on to something that could generate the pulses required. I’m confident the hardware is capable of more, as AccelStepper topped out at less than 5 kHz signal on a 8 MHz chip. Pulsing a pin isn’t a task that requires over 1,000 instruction cycles. Given familiarity with the 3D printer world, I started looking at Marlin which runs on Arduino hardware.

The problem with running Marlin on my Arduino Nano is that I would have none of the associated accessories. No control panel, no SD reader, etc. However, I do have a full control board retired from one of my 3D printers. This board called itself a Melzi Ardentissimo and a search led to the Melzi page of RepRap wiki. Thanks to the open nature of this design, I could trace through its PCB layout. Much to my disappointment, the step and direction signals connected straight from the tiny pin on the main processor to the motor driver without surfacing in an easily tapped fashion. The intent of this board is integration and it’ll be quite some work to defeat that intent in order to decouple the processor from its integrated stepper driver.

Fortunately, I’m not limited to the world of AVR ATmega chips, nor Marlin software. There’s another very capable processor on hand waiting for such project… an ESP32 running Grbl software.

2 thoughts on “Evaluate Retired Melzi Board for XY Stage

  1. I’m going to put a pin in the feasibility of the melzi board running those steppers as I’m a little skeptical that the a4988 drivers can deliver the current needed but that’s not the biggest issue. By the sounds of it you’re looking to tie your nano into the melzi board and then run marlin on it for some reason. This is not feasible. You will need to bootload your board using an ISP or arduino as ISP then install marlin. There is currently no port of grbl for the melzi to my knowledge. I think you should gain a bit of electronics and embedded knowlege if you can.

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    1. It sounds like you have misunderstood my post and got things backwards. The intent is not to drive A4988 with Arduino Uno of the previous experiment, this investigation is to try driving Parker ZETA4 with the ATMEGA MCU on board the Melzi board already running Marlin. But I could not easily tap the pulse & direction output pins from the ATMEGA so I moved on to investigating other ideas.

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