# Repurpose SPI on J10 for SLPI use

Source: https://forum.modalai.com/topic/2720/repurpose-spi-on-j10-for-slpi-use
Category: VOXL 2 and VOXL 2 Mini (https://forum.modalai.com/category/26/voxl-2-and-voxl-2-mini)
Tags: voxl-2
Posted: 2023-10-05 00:23:43 UTC by AndriiHlyvko
Replies: 3 · Views: 943

## AndriiHlyvko · 2023-10-05 00:23:43 UTC

Hi, I would like to recompile the kernel so that the px4 on SLPI can use the SPI bus that's on J10. I looked at the kernel files and I think I understand how each Serial Engine is loaded up with a protocol that it uses. What I dont understand yet is what defines how each processor is able to access that QUP. Can someone help me with this? Maybe point me to some qualcomm documentation? I saw @modaltb configured a lot of the kernel files. Would you be willing to help with this?

Thanks.
Best, Andrii Hlyvko.

## Reply by Vinny (ModalAI staff) · 2023-10-05 17:05:48 UTC

Hi @AndriiHlyvko 
This is not possible.
J10 is hardware set for APPs proc QUP, not SLPI.
![f2288c5d-9139-4b73-801d-476e81d80029-image.png](https://forum.modalai.com/assets/uploads/files/1696525541553-f2288c5d-9139-4b73-801d-476e81d80029-image.png) 

Thanks!

## Reply by AndriiHlyvko · 2023-10-05 18:07:45 UTC (in reply to Vinny)

@Vinny what exactly do you mean by "hardware set"? In the docs it says that 20 QUPs are configured for app processor and 8 for DSP. Cant I reconfigure which QUPs go to which pins in the kernel tree?

## Reply by Vinny (ModalAI staff) · 2023-10-18 21:38:30 UTC (in reply to AndriiHlyvko)

Hi @AndriiHlyvko 
The chip is not infinity flexible. Many things are fixed/set in hardware meaning either the silicon device or the PCB. There is no internal cross-bar in the QRB5165 that allows for 100% remapping like on FPGAs.

Please see these pages:
https://docs.modalai.com/expansion-design-guide/#qups-the-key-io-groups-for-expansion
https://docs.modalai.com/voxl2-qups/

Hope that helps explain things a little.