R ArcaneNibble

WCH QingKe RISC-V XW extension opcode encoding

This has been reverse engineered from the toolchain only and has not been tested on hardware.

The c.lbu, c.lhu, c.sb, and c.sh opcodes replace some standard opcodes (that the QingKe cores do not implement, as the replaced opcodes require the D extension), and they also appear to be compatible with "Huawei" extensions mentioned here.

The c.lbusp, c.lhusp, c.sbsp, and c.shsp opcodes exist in a "reserved" opcode block.

001 uimm[0] uimm[4:3] rs1` uimm[2:1] rd`  00			c.lbu		(replacing c.fld)

JLCPCB Color Silkscreen Crypto

JLCPCB color silkscreen files are encrypted using AES-128-GCM and RSA-2048 with OAEP padding with SHA-256 as the hash function. Unfortunately, this means that, although it is possible for tools other than EasyEDA to create files, only JLCPCB can decrypt the resulting files.

File structure

The structure of an encrypted file is as follows:

256 bytes RSA-encrypted AES key
256 bytes RSA-encrypted GCM nonce

Notes on compiling Python + Rust (PyO3) for wasm32-wasip1

Critical metadata

Date written: 2024-10-30
Python version: 3.12.7
Rust version: 1.82.0
PyO3 version: 0.22.5
zlib version: 1.3.1

	#include <stdint.h>
	#include <string.h>

	#include "CH579SFR.h"

	void write_str(const char *s) {
	for (uint32_t i = 0; i < strlen(s); i++) {
	while (!(R8_UART1_LSR & RB_LSR_TX_FIFO_EMP)) {}
	R8_UART1_THR = s[i];
	}

	def gf2_mult_intermed(a, b, m):
	result = 0
	for biti in range(m):
	if a & (1 << biti):
	result ^= (b << biti)
	return result

	def gf2_reduce(c, p, m):
	# polynomial has an implicit, unspecified x^m term
	c_bits = 2*m-1

	# https://deutsch.ucsd.edu/psychology/pages.php?i=201

	import numpy as np
	import scipy.io.wavfile
	import scipy.special

	f_s = 44100
	duration = 10

	note1 = 392

	/**
	* \file spi.c
	*
	* \brief This is a sample application file which invokes some APIs
	* from the SPI device abstraction layer to perform configuration,
	* transmission and reception operations.
	*
	*/

	/*

	mcpy r_end, r_sta(rt), r_dst

	00000 00 00000 00000 11100000 0001111
	r_dst r_sta r_end MISC-MEM