New ARM Controller Board
Posted by JustAnotherOne
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Re: New ARM Controller Board June 21, 2015 06:22PM |
I'm one of those people who was planning on making an STM32F4 board, and talked to a lot of people getting feedback. I had to drop it, unfortunately, because life got too busy, and linuxCNC-based systems appeared to be gaining ground, which I think have a lot of potential for the high end. I'd be surprised to see someone take the cpu from the beaglebone and put it on a dedicated printer driver board, but it might make for some serious cost savings at scale. But that's another animal 
This looks pretty good, overall. A lot like what I was going to do. Glad to see someone else going for it! A few questions/comments:
If you moved upfrom the 405 to the 407, which has a budgetary cost of about $0.50 more, you'd have the ability to add ethernet at a later time. The LAN8710A or 8720A PHY is pretty cheap, and I'm sure there's chinese equivalents for even less. All you need after that is a magjack and you're good to go. Since a lot of people have previously expressed interest in not needing an rpi or whatever and just plugging in, it might be worth keeping in mind. That said, those ESP8266 wifi modules might be cheaper and more convenient for a lot of people.
I'm very glad to see higher-voltage steppers - faster movement and less heat. The chip you found looks awesome. Is there a reason for having the steppers be modules rather than integrated into the same PCB? Heat? Ability to use less beefy stepper drivers if desired?
If the stepper modules are going to stick out perpendicular to the main board (which can be nice for heat flow), you might want to consider a card edge connector. Some of them are really cheap, like the FCI 10018784-10200TLF, which is only [email protected], compared to the one you picked out which is almost twice as much. That one is rated for lower current, but it has nearly twice as many pins in roughly the same space, and your stepper board wouldn't need a separate connector, saving parts and assembly cost for each stepper board, especially if there's no through-hole parts.
How do you plan to talk to those stepper chips via SPI? It seems like if a module is plugged in, you can't talk to any later ones, which rules out reading the current in use on anything but stepper 0.
Thermocouple: looks like you picked the J-type chip, but the K-type connectors. I'd choose K, because they're cheaper and better suited to the temperature ranges we're looking at. Also, are you planning to always populate the thermocouple circuitry, or just have it there as an option (like my ethernet suggestion above)? I ask because that chip alone seems to be around $3-4 at quantity, and a proper thermocouple connector isn't insignificant either. The expansion port has SPI2 on it, and I get the impression most printers don't use thermocouples, so a thermocouple board could be an add-on. People who use two heads and thermocouples would need to add a second thermocouple anyways, so it would be good to think about that use case. Thermistor circuitry is cheap and tiny, so it makes sense to have a lot of channels available, like you do.
Maybe it's just because they're cool and under $0.10/ea at quantity, but you could consider the WS2812B in place of the red, green, and blue leds on PE10,12,15. It'd free up two pins which might make the routing easier. That said, there's something nice about dedicated indicators with silkscreen labels like "POWER."
I did end up making a design for an L6474-based stepper module, as a drop-in replacement for the standard pololu. Never got around to getting it made. Would it be helpful if I ordered some to verify, and share the design?
This looks pretty good, overall. A lot like what I was going to do. Glad to see someone else going for it! A few questions/comments:
If you moved upfrom the 405 to the 407, which has a budgetary cost of about $0.50 more, you'd have the ability to add ethernet at a later time. The LAN8710A or 8720A PHY is pretty cheap, and I'm sure there's chinese equivalents for even less. All you need after that is a magjack and you're good to go. Since a lot of people have previously expressed interest in not needing an rpi or whatever and just plugging in, it might be worth keeping in mind. That said, those ESP8266 wifi modules might be cheaper and more convenient for a lot of people.
I'm very glad to see higher-voltage steppers - faster movement and less heat. The chip you found looks awesome. Is there a reason for having the steppers be modules rather than integrated into the same PCB? Heat? Ability to use less beefy stepper drivers if desired?
If the stepper modules are going to stick out perpendicular to the main board (which can be nice for heat flow), you might want to consider a card edge connector. Some of them are really cheap, like the FCI 10018784-10200TLF, which is only [email protected], compared to the one you picked out which is almost twice as much. That one is rated for lower current, but it has nearly twice as many pins in roughly the same space, and your stepper board wouldn't need a separate connector, saving parts and assembly cost for each stepper board, especially if there's no through-hole parts.
How do you plan to talk to those stepper chips via SPI? It seems like if a module is plugged in, you can't talk to any later ones, which rules out reading the current in use on anything but stepper 0.
Thermocouple: looks like you picked the J-type chip, but the K-type connectors. I'd choose K, because they're cheaper and better suited to the temperature ranges we're looking at. Also, are you planning to always populate the thermocouple circuitry, or just have it there as an option (like my ethernet suggestion above)? I ask because that chip alone seems to be around $3-4 at quantity, and a proper thermocouple connector isn't insignificant either. The expansion port has SPI2 on it, and I get the impression most printers don't use thermocouples, so a thermocouple board could be an add-on. People who use two heads and thermocouples would need to add a second thermocouple anyways, so it would be good to think about that use case. Thermistor circuitry is cheap and tiny, so it makes sense to have a lot of channels available, like you do.
Maybe it's just because they're cool and under $0.10/ea at quantity, but you could consider the WS2812B in place of the red, green, and blue leds on PE10,12,15. It'd free up two pins which might make the routing easier. That said, there's something nice about dedicated indicators with silkscreen labels like "POWER."
I did end up making a design for an L6474-based stepper module, as a drop-in replacement for the standard pololu. Never got around to getting it made. Would it be helpful if I ordered some to verify, and share the design?
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Re: New ARM Controller Board December 22, 2015 07:44PM |
the complete package then looks like this:
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Re: New ARM Controller Board December 23, 2015 11:45AM |
Hey ambrop7,
The more software that runs on the board the better!
The 405 and 407 share the same data sheet. Supporting it should be just a matter of configuration. I did not find the place where I could do that in your firmware. The Pin Out should be clear from the schematic.
Does your firmware support the Trinamic TMC262 chips? I thought there should be something for them here.
I would like t help you more with your Firmware, but I fear I might fall into "average C hacker" group.
If I can do anything else to help you get the board supported just let me know.
Cheers,
Lars
PS: The Ethernet Interface of the Board is directly between the Power Input and the 4 USB Ports.
The more software that runs on the board the better!
The 405 and 407 share the same data sheet. Supporting it should be just a matter of configuration. I did not find the place where I could do that in your firmware. The Pin Out should be clear from the schematic.
Does your firmware support the Trinamic TMC262 chips? I thought there should be something for them here.
I would like t help you more with your Firmware, but I fear I might fall into "average C hacker" group.
If I can do anything else to help you get the board supported just let me know.
Cheers,
Lars
PS: The Ethernet Interface of the Board is directly between the Power Input and the 4 USB Ports.
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