Join Scott as he continues his quest to get TinyUSB running on the Raspberry Pi 4 and answers questions folks have. Support Adafruit, and by extension me, by purchasing hardware from https://adafruit.com

Chat with me and lot of others on the Adafruit Discord at https://adafru.it/discord.

No stream next week!

Latest code is here: https://github.com/tannewt/tinyusb/tree/rpi

0:00 Getting started

0:01:30 audio debrief from last week

0:03:28 housekeeping

0:08:00 First time watching your live stream. What are we learning today?

0:09:10 Cortex A / MMU

0:10:20 ​If you learn original python on a pc, is it then easy to go from there to circuit python?

0:11:10 qemu further progress

0:13:40 board init()

0:15:30 unaligned access

0:17:30 What model of Pi will this run on? And will it be ARM32 or 64?

0:19:10 if you run CP on metal RPI4, is there the need for 32 bits?

0:21:15 local setup on desk

0:22:30 OSH Park Pi Development v1 project to eliminate all the wires above

0:25:00 https://github.com/chickadee-tech/pi-developer

0:25:45 catch the exceptions in boot.s

0:27:40 load VBAR_EL1 with virtual vector table address

0:29:00 arm stub switches from EL3? to EL2

0:29:40 4-way split terminal tinyusb, serial, gdb

0:32:22 cortex-a.py (in gdb)

0:32:47 ARM Cortex-A Programmers Guide for ARMv8-A pdf (MMU overview)

0:34:15 TTBR0_EL0 (EL2)

0:35:10 Arm architecture reference DDIO487G_b_armv8_arm.pdf

0:35:51 ESR_EL2 register

0:38:42 cortex-a.py - decode exception code

0:40:15 Python pattern matching in python 3.10 (match switch)

0:41:45 What other information can we extract from the exception

0:42:25 FAR ( fault address register? ) / extend the decoding

0:50:45 ashw.io/blog/arm64-pgtable-tool - and youtube video

0:54:00 decoding virtual address ( from BruceS )

0:56:20 pi4 address map from bcm2711-peripherals(1).pdf

0:58:00 setup_mmu_flat_map() in mmu.c

1:00:10 Level 1 access flag fault

1:02:00 Translation fault level 1

1:03:30 access flag fault level 1

1:06:20 Long-descriptor level 1 and level 2 descriptor formats

1:10:00 github ashwio/arm64-pgtable-tool python code

1:14:10 “The Access flag” , ok, add the MM_DESCRIPTOR_ACCESS_FLAG

1:17:10 got a little further - maybe try it out on the hardware (instead of qemu)

1:22:30 decode the Data Abort further - translation fault level 1

1:27:50 we have uart output!

1:29:00 summary - flags in translation table needed to get access flag set to 1

1:39:00 dcd_init()

1:39:58 What side projects are you looking forward to diving deeper into in the coming weeks?

1:42:00 Did you ever ask adafruit to manufacture your old board?

1:44:04 UPS truck arrived - (new iPhone? ) Be right back

1:45:58 back - unboxing

1:51:45 recap - MMU / fixed table lookup / added access flag / used python to decode information about access fault / uart output

1:53:00 next steps

1:53:54 wrap up

1:55:50 - see you in two week

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