Scott recaps work on the Raspberry Pi running CircuitPython and then continues working on SD card support.

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0:00 Getting Started

09:32 Housekeeping

13:00 Raspberry Pi Zero 2 W discussion

19:50 raspberry pi .org vs. .com

20:51 Dune and DOS

21:49 USB Host and Tiny USB

23:07 Edit code on a Pi over BLE

23:38 working on Pi 400 steps to figure out

24:14 Pi-DOS project mention

26:00 Glasses come off / glasses setup

27:00 Pi Zero - epic for CP with .5 GB RAM

29:00 Zero 2 is the ultimate board for CP!!!

29:50 Review last week’s status -

30:00 Now Tac has High Speed working

31:08 Last week - HDMI was very slow - investigate caches off/on

31:38 Not caching “enough”

32:48 Scrolling demo, much faster than last week, caching on for everything

33:42 Tweek resolution

34:00 “what is CP”

35:15 Still Broadcom chip

36:14 Flash speed vs. run from RAM

37:37 once I get the SD card working, there will be some re-organization for all the boards

38:20 experiment with screen resolutions, to demo refresh performance

40:17 640x480 REPL - pretty quick

42:00 1080p seems blurry

43:10 Are there any plans to make this a simpler process, eg moving it to a Java IDE?

Suggested https://codewith.mu/

45:10 check out visual studion circuitpython plugin

47:11 Python 3.10 has deprecated “distutils”. Spent my day on that for Yocto Project. It’s nice to not need to worry with CP

48:00 rebooted to ‘lower’ resolution

48:30 flash wear discussion Nand flash, Nor flash, flash protocol

49:36 Should you have some knowledge of Python before learning Circuit Python?

50:00 Pi4 is ARM64....so theoretically you could port CPY to the M1 chip

50:32 core of CP is just like Python

50:57 SD Cards technical proprietary, but …

51:27 Why use bare-metal CP over blinka ( ease of setup, just does one thing )

52:20 Implementation

53:11 adafruit_sdcard.py - SPI 1, 4 or 8 bits at a time

54:15 here is a lot of IO stuff that you couldn't do under a Linux kernel like bitbanging is quite hard/limited in a non realtime OS

55:16 raspi3-tutorial / 0B_readsector / sd.c

56:39 habits that lead to more reusable code :-)

57:04 declaring 5 global variables on one line with no comments

57:37 SBD generated structs vs.

58:05 multiple things on one line - suggest using curly braces freely

59:00 initializing some but not all variables ( on one line )

59:26 ‘weird’ globals

59:39 q:is there a native async library in circuitpython? I found a library called "asynccp" it works for me now but it would be better to use the native way.

1:01:04 use single letter variables sparingly

1:02:06 perhaps run it through a formatter

1:02:18 “I still don’t know what this code does” :-)

1:02:55 consider naming style for global variables

1:03:15 ‘circle’ reference gighub rsta2/circle - well commented

1:04:10 check out the license

1:06:04 sdcard.org PDFs

1:06:44 Scott’s Pi Zero arrives on Monday!

1:08:11 640x480 HDMI raspberry pi bare metal REPL demo - last piece is SD card reading in CP - connect to USB mass storage

1:09:40 goal: read SD card over USB

1:10:29 Exception levels - switch from EL2 to EL1 ( os exception level ) CP is running EL1

1:12:00 Waiting for high speed to be merged into tiny USB

1:12:40 HDMI output used for display IO

1:14:40 Looking at board.c in CP ports/broadcom/boards/PI4

1:15:15 sdioio API

1:15:35 “with this big chonky font, CP needs to implement CBM ASCII to get cool map-building "letters"”

1:15:42 detour - fantasy console - mimic but modernize

1:16:34 nerd fonts project (nerdfonts.com)

1:18:00 Does circuitpython use Unicode strings?

1:18:14 Twitter emojis opensourced twitter/twemoji

1:19:44 displayio doesn't display it yet - though emoji variable names do

1:24:30 in cpython you can only use unicode characters in variable names if the belong to the "letter" class, so you can do accented characters, or Chinese, or Hebrew, but not emoji

1:25:37 back to sdioio/SDCard.c

1:27:54 second argument to SD send command - refer to adafruit_sdcard.py

1:30:50 SD Specs - commands , and back to adafruit_sdcard.py

1:39:03 bztsrc/raspi3-tutorial 0B_readsector/sd.c sd_cmd() / 32-bit commands vs BCM2835 ARM Peripherals.docx

1:41:21 Q: been experimenting with the sdcard module on circuitpython but it stops the code if there is no card in the reader

1:42:36 consider the response type ( number of bits )

1:43:54 sdioio/SDCard.h

1:45:03 sdcard.org Part1_Physical_Layer_Simplified_Specification_Ver800.pdf r2 response codes

1:48:57 autogenerated SVD generated file bcm2711_ipa.h

1:52:45 sdcard.org Design Guide « Whitepaper » is a pretty cool resource. https://www.sdcard.org/cms/wp-content/uploads/2020/11/SD_Express_Design_Guide.pdf

2:04:00 CM4 Appendix B - ordering codes ( wireless, eMMC, RAM )

2:06:15 Wrap up - next week Pi Zero on Friday

2:09:35 have a great weekend