I have found that the nRF52840 is not capable of being a USB host, it's peripheral only. I've concluded that from this devzone post and this infocenter entry.
You can use a microcontroller with USB host functionality and another communication protocol compatible with the nRF52840 or a USB bridge IC. I'm doing the same thing at the moment using an SPI to USB bridge.
guys do you have tried the Vinculum-II? I also want to connect a nRF5840 to a CDC Modem using AT commands a give it cellular functionality. at the moment no luck to make work the Vinculum II
I've been out of the project for over a year now, so don't have the specifics available anymore.
You indeed have to use the Nordic SPI to configure the MAX3421E. First set the SPI communication bits on the MAX. Then make sure you can read the revision number of you MAX to confirm SPI communication. After that you can set the HOST bit on the MAX. Specifics on how to program the chip can be found in the MAX3421E programming manual on the website of Maxim Integrated.
Back then I wrote my own code to use the MAX3421E, but after I was finished I found some open source code on github to do exactly that. You might be able to find it.
I have a nrf52840-DK and Arduino USB Host Shield combo. Setting communication bits is just fine, I also can read the revision number.
I've stuck over a problem though. In code examples you've specified there is a loop waiting for OSCOKIRQ for PLL/internal oscillator to stabilize. Same loop is in every code for MAX3421e I was able to find.
OSCOKIRQ is never set on for me. There is a thread at Electrical Engineering StackExchange claiming it is a bug in MAX3421e. I doubt this is the case, it certainly would be noticed, at least by felis/USB_Host_Shield_2.0.
I am running nrf52840-DK connected and powered via USB, nothing is connected to the shield, I can set communication bits and read revision number. So I guess it is enough power for PLL, right?
My question is - have you seen this problem in your project? Was waiting for OSCOKIRQ working for you? Or you've just skipped this stabilization part?
Sorry for bugging you, but I am really desperate right now. (
As I have mentioned before, I haven't worked on this project in a long time.
I do however remember something along the lines of OSCOKIRQ not being set, and actually read the same thread at stackexchange. I think the problem back then was a lack of power because the nRF52840DK cannot provide enough current to the MAX3421E-EVKIT.
Try looking up the power specification for you board and checking if you're providing enough. If not, use an external power source.
As I have mentioned before, I haven't worked on this project in a long time.
I do however remember something along the lines of OSCOKIRQ not being set, and actually read the same thread at stackexchange. I think the problem back then was a lack of power because the nRF52840DK cannot provide enough current to the MAX3421E-EVKIT.
Try looking up the power specification for you board and checking if you're providing enough. If not, use an external power source.
