This repository contains the EtherCAT devices I have designed, built and put in use in linuxcnc.
Everything should be here:
- Schematics, PCB layouts, and what is needed to build the boards.
- Software tools to create an ESI-file and program the ESC eeprom.
- Software tools to create the application running on a STM32F407VG.
- A big learning curve is hidden in here as well
I have (so far) used two different ESC ICs: LAN9252 and Ax58100. Both work, I can't really see a difference. The Ax58100 has a leg spacing of 0.4 mm, 0.5 mm for the LAN9252, if that matters. On paper the Ax58100 has more builtin functionality like stepper motor drivers, but the documentation is lacking. Or my understanding of the documentation is lacking. The Ax58100 supposedly has more efficient access to registers and data. The indirection scheme is the main objection to using LAN9252, I have read. The LAN9252 is the true and tested IC of the two. If you don't know, go for the LAN9252.
The EtherCAT cards, which I call EaserCAT cards, often use an EtherCAT chip and a normal MCU. I have used the STM32F407VGT6. The EaserCAT chip does the network talk and other EtherCAT things. The STM32 does the application things, like reading and setting pins high or low, reading encoder inputs, generate stepper motor pulses and other interesting applications one can think of. There is a narrow interface between the two: SPI and a couple of lines for synchronization. Any decent MCU can do that, it doesn't have to be a STM32F407VGT6. I have tested with a esp32 with success. Feel free to experiment with other processors.
I learned most of what I know about EtherCAT through a number of Youtube Videos I made. There are accompanying git branches. For example, for video 8 you can check out the Video8 branch to get the software tree in the state at the video. More info on the videos, which are now more of historical interest, but also a bit of learning by following this link
Here is the start of building instructions
This was the first card that got used in Linuxcnc. Follow link here I think I got it working pretty well in the end. There was, and still is, an issue with synchronization between the linuxcnc servo-loop and the ESC DC loop. I don't remember the status of it anymore, it was some time ago I worked with it. The main thing was that it lacked optocouplers and isolation for the external signals.
This card is an evolution of the EaserCAT 2000 and was intended to be used in my plasma cutter. It features four stepper driver outputs, input for a THCAD arc voltage card, an encoder, an analog output (for spindle +- 10V), eight digital inputs, four digital outputs, plus some 12 I/O for any possible extension. The IOs are isolated from the MCU.
However, I couldn't get this card to work, almost at all. The Ax58100 didn't even load the eeprom. Struggling with the documentation for the Ax58100, which formed my negative opinion about that, I gave up and let it sit for over half a year. It was first when someone came and asked questions around it I had another look. I built a new board, and it all started to work. At time of writing it all seems to work.
Faced with the problems with the EaserCAT 3000 board, and still wanting to use EtherCAT
in my upcoming plasma cutter, I made this board whos single purpose is to read
the PWM frequency from Mesa's THCAD board.
The THCAD board reads the voltage between
the plasma torch and the workpiece which is around 100V. Highly isolated, and with
a voltage to frequency converter it delivers a differential pwm signal.
The frequency of this signal can be related to the voltage.
That's what is needed for linuxcnc torch height control.
In the tests on the bench this can read at least up to 200 kHz, but its's better to be below 100 kHz.
The THCAD has a frequency divider one can set to make the frequency range nicely match this.
It seems to work fine so far.
Implementation is with interrupts.
A better option would have been to use TIM2's PWM_INPUT function, which can work with several MHz frequency.
I tried the PWM_INPUT method a lot but couldn't get it to work. The current method still works, though.
If time and interests are in phase with the moon, I might look at PWM_INPUT again.
This board is now relegated to history, replaced by the EaserCAT-6000.
A card just doing Digital Input and Digital Output. The intentions were to read limit switches and some other switches around the plasma torch. And to switch on the plasma torch. It's a single LAN9252, configured for local IO. Optocouplers are attached to IO pins for isolation. It has been tested on the bench, it works with TwinCAT.
HOWEVER, it doesn't work, and will not work, with linuxcnc. As I've learned, the IgH EtherCAT master needs a CoE client (CANopen over EtherCAT). The LAN9252 in DIO mode is only an EtherCAT client and can't be turned into a CoE client. And the IgH EtherCAT application interface for real-time communication can not be downgraded to work with a pure EtherCAT client, it requires a CoE client.
To add CoE functionality means to add number of objects at certain positions in the client and that can not be done to the LAN9252. It is what it is. In a setup with LAN9252 with MCU, those objects are created in the firmware, so there it works.
This board is now relegated to history, replaced by the EaserCAT-6000.
Finally, a card that's actually used in a real system. This card is used in my plasma cutter.
It has 12 digital inputs, 4 digital outputs and a frequency counter to get
the input from Mesa's THCAD (reader of voltage between plasma nozzle and workpiece).
All digital IOs are opto-isolated and the frequency input uses a RS-485 receiver.
In the plasma cutter, it does the job. There are three ECT60 stepper motor drivers.
And the EaserCAT-6000 card. It handles limit switches for X, Y and Z, floating switch,
break-away switch, and plasma Arc OK signal. There is room for e-stop and other switches.
The plasma torch is switched on using one of the digital outputs.
THCAD is an older model with full voltage input. Frequency divider is set to 1/32.
This board replaces EaserCAT-4000 and EaserCAT-5000.
A few weeks later and I've used this card in the plasma cutter for quite a bit of cutting and it hasn't missed a beat. Works so well. THC follows the sheet surface up and down. Awesome.
Don't violate the original licenses. No warranties. Use it any way you like.
Remember: It is a hobby project, not a product.