How to write a driver for sc16is752 - i2c dual uart

[Marshall]

Hi There

I didn't realise when chosing the nrf9160 that the peripherals were all shared, to a maximum of 4 serial type devices, (any combo of i2c, spi or uart to a max of 4 devices) 

I've used all the devices and need an additional serial port. I have a sc16is752 on the board, i2c -> dual uart expander. I'm struggling on how to get started to integrate this into zephyr as a driver so that I can use it as a normal serial port within zephyr. 

Are there any pointers that could be useful, I'm more than happy to contribute it back to the community when its done. 

Thanks 

Marshall

[Kenneth]

Hello,

Please check out the following github repo (with example project and video for adding a sensor):
https://github.com/teslabs/zds-2022-drivers-app 

In your case you will need add a bindings/serial instead of bindings/sensor (and drivers/serial instead of drivers/sensor etc), but conseptually it should be the same. In addition to study the example on github you can also look for instance at how usb, rtt or uart have implemented serial in the corresponding folders.

Best regards,
Kenneth

[Marshall]

Thanks, after a lot of effort, I've written it. it can now be used as a serial port in zephyr, complete with interrupts and callbacks etc. 

I used the "uart_ns16550.c" as an example as this has almost the same register mapping. 

If anyone wants to finish it off and add into the zephyr mainline I'm more than happy to share it. 

I'm not experienced in submitting pull requests to Zephyr, and don't have the resources to make it match any submission criteria. 

I'd be keen to see how the second serial port is implemented (I've done most of it) 

Regards

Marshall

[Rokk Research]

Hi Marshall, I'm interested as we are considering this device as well.  Is your driver hosted on GitHub?

[Marshall]

No it's not on Github

I'll email it to you and you can do it if you want. 

[Sashi]

this is great. I was just looking for something like this.  can you emai me it as well, or if you do post to github can you share the link. 

[Marshall]

I'll figure out how to post to Github, as emailing it to everyone is going to get messy really fast,

[Marshall]

Try this, 

marshallbrown123/sc16is7xx_zephyr_driver: Zephyr driver for the NXP I2C SC16IS7XX dual UART (github.com)

Rokk Research  if you can use this as well, it's probably cleaner. 

Regards

Marshall