Possible new Hardware Version

[Kai Wolter]

Hi everybody.

The last days I worked on a new hardware version for the Mechaduino (no Tropical Labs official version). Since I am not an electrical engineer, it would be nice if someone were willing to look at the schematics. In addition, maybe some other people are interested in the newer/changed design.

 

The key features (compared to the current hardware):

   - SAMD51 processor running at 120 MHz (old version: SAMD21 running at 48 MHz)

   - Floating point unit (integrated in the SAMD51. I'm not sure how to use it with the Arduino IDE, or if it's even possible, but when it should speed up some parts of the code as well)

   - 2 x 12bit DAC running with 1 MS/s to control the Coil current

   - 1 thermistor input with low-pass filter to monitor the coil temperature

   - Level shift IC with 4 channels (simpler PCB layout)

   - removed extra pins (to keep the PCB simple. I do not know how much people are using the extra pins)

 

 

GITHUB link:

Schematics
Repository
 

When I finish the board, I will probably will manufacture some small amount of them in china. So please let me know if you are interested and if you want some other changes and thinks like that.

 

Sincerely

Kai

 

[Kai Wolter]

What I forgot to mention:

The SAMD51 is the new processor of the Adafruit Metro M4. Therefore, Adafruit handles the Support for the Arduino IDE. I coundn’t find the schematics of the board, but maybe someone else can find it.

[Kai Wolter]

I have uploaded new Eagle files with the current PCB design. I also changed to the SAMD51 with a TQFP64 footprint, since the Adafruit Metro M4 also uses this chip version.

The current Adafruit hardware support for the ATSAMD51 currently doesn't include the TC counter like the ATSAMD21 so I've posted a question in the Adafruit forum maybe they will include it in the next version. If so I think, I will order some PCBs.

[Kai Wolter]

Current PCB layout without the ground fill:

[Kai Wolter]

I have also found a forum topic with comparison in speed of the controllers and it seems that the ATSAMD51 is more than 3.3 times faster for integer operations and up to 91 times faster for floating point operations!

https://forums.adafruit.com/viewtopic.php?f=63&t=134765&p=668956&hilit=metro+m4#p668956

[Pablo Vila Ferrero]

Awsome work Kai. The two 12bits DACs are very tempting, although I'm just aiming for 1um resolution with 5mm pitch ballscrews, I will keep working on the high power version, I got it somewhat working the other day, but need to make more test. Bad thing I must change the mechaduino software to make it work.

[Kai Wolter]

I do not know much about the ESP but I thought it would work with the Arduino IDE :/

 

The two DAC with the high precision are more like a benefit. I was aiming for a fast microcontroller that works the same like the ATSAM21 and hast two DACs at all.

 

How much power do you need? You could try to use the A5965 which can handle up to 3.2 A.

 

I have finished the PCB design today and uploaded it to GITHUB and to a manufacturer. Let’s see how much 5 board will cost.

[Pablo Vila Ferrero]

Is not only about amps on stepper motors, voltaje is what limits your max torque at high speed. Now I'm aiming for 72V and 6A using IRF540, although it could be way more just by selecting other mosfets.

I bought my first boards at seeedstudio. They gave you a welcome discount of 5USD, so it was 15USD for 10 boards. The next ones where from JLCPCB, they had an offer of 10 boards (I only got 6) for 2USD with free shipping, but now is gone. If I had to select now I would go for seeedstudio, board quality was quite better.

[Kai Wolter]

Ok. You’re right. I didn’t thought about the voltage.


I’ve already ordered some other PCBs from PCBWay with pretty good quality. The Problem with this one is that I can’t solder the small components by myself. So I want to get assembled versions which is going to be much more expensive. I will post a Update when I get a quote from PCBWay.

[Kai Wolter]

I have uploaded a new version of the PCB with some changed components (changed to fit mostly seeed studio parts). The newer version has now all input pins level shifted (including I2C).

 

I also ordered some PCBs from Seeed. They are quite expensive because of the small quantity (about 50€ for one Board).

 

If everything works and is fine I may order more boards and sell them (if anybody is interested) this should make the board cheaper.