view cp2102/decode_baudtab.c @ 67:742c41f44658

doc/FTDI-chip-ID: new article
author Mychaela Falconia <falcon@freecalypso.org>
date Wed, 13 Sep 2023 00:43:14 +0000
parents 672c7adc8bc9
children
line wrap: on
line source

/*
 * The function implemented in this module decodes the baud rate table
 * contained in the captured CP2102 EEPROM image.
 */

#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include "cp210x_defs.h"

extern u_char eeprom[SIZE_EEPROM];

void
decode_baud_table(outf)
	FILE *outf;
{
	unsigned entry;
	u_char *dp;
	unsigned baudrate, baudgen, timegen, prescaler, sparebyte;
	unsigned baud_div, calc_baud, time_us;

	dp = eeprom;
	for (entry = 0; entry < SIZE_BAUDRATES; entry++) {
		baudgen = (dp[0] << 8) | dp[1];
		timegen = (dp[2] << 8) | dp[3];
		prescaler = dp[4];
		sparebyte = dp[5];
		baudrate = dp[6] | (dp[7] << 8) | (dp[8] << 16) | (dp[9] << 24);
		dp += SIZE_BAUDRATE_CFG;
		fprintf(outf, "baud-entry %2u: %7u = %04X, %04X, %u, %u",
			entry, baudrate, baudgen, timegen, prescaler,
			sparebyte);
		if (prescaler) {
			baud_div = (0x10000 - baudgen) * prescaler;
			calc_baud = 24000000 / baud_div;
			fprintf(outf, "\t# %u baud, ", calc_baud);
			time_us = (0x10000 - timegen) * 2;
			if (time_us >= 1000)
				fprintf(outf, "%u.%03u ms", time_us / 1000,
					time_us % 1000);
			else
				fprintf(outf, "%u us", time_us);
		}
		putc('\n', outf);
	}
}