Support for new board coming up: Tang Nano 20k

[Peter-van-Tol]

I'm happy to announce that LiteX-CNC will support the Tang Nano 20k in the near future. Sipeed was kind enough to send a sample to be used as test-bed. A HAT for using the Tang Nano with a RapsberryPi has been drafted. This HAT will provide:

• 7 extended PMOD connectors, each providing 4 GPIO, power and the ENA-signal from the watchdog;
• 1 RS489 connection for connecting a VFD.

This HAT will provide with 28 GPIO, which can be used for a config with:

• ESTOP in;
• 4 stepgen (8 GPIO in total)
• 4 home switches (4 GPIO)
• 3 inputs (ALARM, toolsetter, probe)
• connection for MPG (with handwheel, axis selection, speed selection, start, stop and E-Stop) - 11 GPIO in total

Advantage of using the Tang Nano is that you don't need to replace buffers and the inputs are 5V tolerant from the factory. When 28 GPIO is sufficient, then this board looks promising.

[Peter-van-Tol]

Design is 95% finished. Last things to do are:

• adding poly-fuses to the 5V rail of each connector
• adding LED indicating the enable status

This final features of this board:

• 7 extended PMOD connectors, each providing 4 GPIO, power and buffered ENA-signal from the watchdog;
• 1 RS489 connection for example for connecting a VFD;
• 3-wire SPI-connection (bi-directional mode);
• conforms to HAT+ design specification, with EEPROM storing information on the overlays.
• all components are placed on the bottom of the board, so it can be assembled for a reasonable price. The hand-soldering is limited to the through-hole components (connectors and Tang Nano) and adding the three LEDs on the front of the board.

The price of the board is around 6 Euro, based on 5 boards. This includes all parts, except for the Tang Nano 20K. When increasing the number of boards to 10, the price drops to 5 Euros.

[Nserega90]

This is very cool!!!!

[Peter-van-Tol]

Today I've received my test-board ❤️ .

Also started to draft the first firmware for the board, which compiled successfully. Some minor hick-ups along the path:

• there is a small bug in litex_boards, pin 75 is missing from the connector. This means all pins are shifted. PR will be send to LiteX to fix this;
• the frequency of the FPGA is fixed to 27 MHz. In the logs I also saw 12 MHz passing along. Have to check what the actual clock-speed is of the board. The frequency of 27 MHz also excludes the use of ethernet as this requires 125 MHz. As an alternative a module as W5500 can be used (no support planned yet). The focus is to get this board working with a RPi, thus SPI is enough for now. Please send a feature request when support for W5500 is requested.

The toolchain used is apicula, which is open-source. The package oss-cad-suite, which can be installed using litexcnc install_toolchain already contains this toolchain! So it works more-or-less out of the box.

Tomorrow I'm going to flash the board.

[Peter-van-Tol]

[Peter-van-Tol]

Today celebrated a success. The first communication between the Tang Nano 20K and LinuxCNC (halrun):

Note: Using POSIX non-realtime
halcmd: loadrt litexcnc connections="spidev:/dev/spidev0.0"
litexcnc: Loading Litex CNC driver version 1.3.1
litexcnc: Loading and registering default modules:
litexcnc: Registered module gpio
litexcnc: Registered module pwm
litexcnc: Registered module encoder
litexcnc: Registered module step
litexcnc: Setting up board drivers: 
litexcnc: Registered driver spidev
litexcnc: Setting up modules...
litexcnc:  - Watchdog
litexcnc:  - Wallclock
litexcnc: Creating read and write buffers...
litexcnc: Base addresses: init: 00000000, reset: 00000024, config: 00000028, write: 00000028, read: 0000002C 
litexcnc:  - Write buffer: 4 bytes
litexcnc:  - Read buffer: 12 bytes
litexcnc: Exporting functions...

At this moment LiteX-CNC can build the bit-stream for this board. However, I didn't manage to flash the board using openFPGALoader. For flashing the board the Gowin Programmer is required, which is Windows only. I'll add a jumper on the board to isolate the FPGA temporarily when flashing the board from an external PC.

Hopefully this issue will be resolved soon: https://github.com/trabucayre/openFPGALoader/issues

In the mean-time: this gives me enough confidence that the board will work. Going to continue on designing the HAT. I want to make the inputs 5V tolerant by adding 4 buffers, but space is very limited....

[Nserega90]

Hi Peter! I started following your projects quite recently! I really like what you do! It's really, really cool! Of course, special thanks to Romanetz! Why did I start taking an interest? I recently bought myself an old 1M61 lathe. I was looking for a control board for LinuxCNC for a long time that would suit my budget. Mesa is an expensive board for me. And I started searching. And here I am!!!!))) I am very grateful for the work you have done! Now I want to order a 5A-75E board, but suddenly I saw your new project))))). Now I need to decide on the number of inputs/outputs to choose a board))) I don't understand Linux well, maybe I will contact you for help! thank you!

[Peter-van-Tol]

Your welcome!

When you have questions, feel free to post them in the Discussions. To prevent clutter, please open a new topic for your machine.

The best way to make the decision which board is best for your machine, is to list all the functions you have:

• how many stepper motors / axis. Each axis requires at least 2 outputs for your step and direction;
• how many encoders do you have (don't forget your spindle). Each encoder at least uses 2 inputs for A/B. When you spindle has an encoder, it will most likely has a Z-index and thus requires an extra input. Also the cheap rotary encoders for a user panel are in this category.
• how many inputs do you need? Home inputs, E-stops and the ALARM of the stepper drivers should be connected directly to the GPIO of the FPGA.
• port expansion (NOTE: feature under development): Using 4 GPIO of the FPGA, you can add basically unlimited GPIO out or GPIO in using shift registers such as the 74HC595 for GPIO out and the 74HC164 for GPIO in.

The Tang Nano 20K board offers in total 28 GPIO out. If your configuration can stay below this amount of GPIO, you should think of using the Tang Nano 20K. Otherwise, the 5A-75B will be a better choice. With the 5A-75B you have to modify the buffers!

[Peter-van-Tol]

For example, the config for my CNC mill would require:

• 4 stepgen: 8 GPIO;
• 4 home switches: 4 GPIO
• E-stop: 1 GPIO;
• stepgen ALARM: 1 GPIO;
• MPG:
  • handwheel: 2 GPIO;
  • axis selector, speed selector, run program buttons: using shift_in, this requires 4 GPIO;

Total GPIO used 20 GPIO! This leaves me with room to spare for future additions, such as shift_out for controlling coolant, shop-vacuum, etc.

[Peter-van-Tol]

Another example for my lathe would be:

• 4 stepgen (X, Z, spindle, toolchanger): 4 GPIO;
• 2 home switches: 2 GPIO + 1 for toolchanger;
• spindle encoder: 3 GPIO (including Z-index);
• E-stop: 1 GPIO;
• stepgen ALARM: 1GPIO;
• user panel:
  • LED's: 4 GPIO using shift_out
  • buttons and selectors: 4 GPIO using shift_in
  • encoders for feed, speed and spindle override: 6 GPIO.

In this case I require 26 GPIO (I'm still surprised that this is it!), so it still fits on Tang Nano, with room to spare...

[Nserega90]

Thank you very much for the detailed answer! Yes, I will sit down in my free time in a few days and count how much I will have! And of course I will make a small reserve for expansion in the future! Thanks again, I will not clutter this thread! In the future I will create a new discussion! See you!