From f15786e4a4fdb935f639e16ab69d717f3d29bd2b Mon Sep 17 00:00:00 2001 From: Uwe Bonnes Date: Tue, 12 Jul 2011 17:49:18 +0200 Subject: [PATCH] Rewrite the baudrate calculation, tested for 232R and 232H --- src/ftdi.c | 165 +++++++++++++++++++++++++++++++++++++++++++----------------- 1 files changed, 119 insertions(+), 46 deletions(-) diff --git a/src/ftdi.c b/src/ftdi.c index dca79e1..66c159e 100644 --- a/src/ftdi.c +++ b/src/ftdi.c @@ -964,34 +964,30 @@ int ftdi_usb_close(struct ftdi_context *ftdi) return rtn; } -/** - ftdi_convert_baudrate returns nearest supported baud rate to that requested. +/* ftdi_to_clkbits_AM For the AM device, convert a requested baudrate + to encoded divisor and the achievable baudrate Function is only used internally \internal + + See AN120 + clk/1 -> 0 + clk/1.5 -> 1 + clk/2 -> 2 + From /2, 0.125/ 0.25 and 0.5 steps may be taken + The fractional part has frac_code encoding */ -static int ftdi_convert_baudrate(int baudrate, struct ftdi_context *ftdi, - unsigned short *value, unsigned short *index) +static int ftdi_to_clkbits_AM(int baudrate, unsigned long *encoded_divisor) + { + static const char frac_code[8] = {0, 3, 2, 4, 1, 5, 6, 7}; static const char am_adjust_up[8] = {0, 0, 0, 1, 0, 3, 2, 1}; static const char am_adjust_dn[8] = {0, 0, 0, 1, 0, 1, 2, 3}; - static const char frac_code[8] = {0, 3, 2, 4, 1, 5, 6, 7}; int divisor, best_divisor, best_baud, best_baud_diff; - unsigned long encoded_divisor; - int i; - - if (baudrate <= 0) - { - // Return error - return -1; - } - divisor = 24000000 / baudrate; + int i; - if (ftdi->type == TYPE_AM) - { - // Round down to supported fraction (AM only) - divisor -= am_adjust_dn[divisor & 7]; - } + // Round down to supported fraction (AM only) + divisor -= am_adjust_dn[divisor & 7]; // Try this divisor and the one above it (because division rounds down) best_divisor = 0; @@ -1009,11 +1005,6 @@ static int ftdi_convert_baudrate(int baudrate, struct ftdi_context *ftdi, // Round up to minimum supported divisor try_divisor = 8; } - else if (ftdi->type != TYPE_AM && try_divisor < 12) - { - // BM doesn't support divisors 9 through 11 inclusive - try_divisor = 12; - } else if (divisor < 16) { // AM doesn't support divisors 9 through 15 inclusive @@ -1021,23 +1012,12 @@ static int ftdi_convert_baudrate(int baudrate, struct ftdi_context *ftdi, } else { - if (ftdi->type == TYPE_AM) + // Round up to supported fraction (AM only) + try_divisor += am_adjust_up[try_divisor & 7]; + if (try_divisor > 0x1FFF8) { - // Round up to supported fraction (AM only) - try_divisor += am_adjust_up[try_divisor & 7]; - if (try_divisor > 0x1FFF8) - { - // Round down to maximum supported divisor value (for AM) - try_divisor = 0x1FFF8; - } - } - else - { - if (try_divisor > 0x1FFFF) - { - // Round down to maximum supported divisor value (for BM) - try_divisor = 0x1FFFF; - } + // Round down to maximum supported divisor value (for AM) + try_divisor = 0x1FFF8; } } // Get estimated baud rate (to nearest integer) @@ -1065,19 +1045,112 @@ static int ftdi_convert_baudrate(int baudrate, struct ftdi_context *ftdi, } } // Encode the best divisor value - encoded_divisor = (best_divisor >> 3) | (frac_code[best_divisor & 7] << 14); + *encoded_divisor = (best_divisor >> 3) | (frac_code[best_divisor & 7] << 14); // Deal with special cases for encoded value - if (encoded_divisor == 1) + if (*encoded_divisor == 1) + { + *encoded_divisor = 0; // 3000000 baud + } + else if (*encoded_divisor == 0x4001) + { + *encoded_divisor = 1; // 2000000 baud (BM only) + } + return best_baud; +} + +/* ftdi_to_clkbits Convert a requested baudrate for a given system clock and predivisor + to encoded divisor and the achievable baudrate + Function is only used internally + \internal + + See AN120 + clk/1 -> 0 + clk/1.5 -> 1 + clk/2 -> 2 + From /2, 0.125 steps may be taken. + The fractional part has frac_code encoding +*/ +static int ftdi_to_clkbits(int baudrate, unsigned int clk, int clk_div, unsigned long *encoded_divisor) +{ + static const char frac_code[8] = {0, 3, 2, 4, 1, 5, 6, 7}; + int best_baud = 0; + int divisor, best_divisor; + if (baudrate >= clk/clk_div) + { + *encoded_divisor = 0; + best_baud = clk/clk_div; + } + else if (baudrate >= clk/(clk_div + clk_div/2)) + { + *encoded_divisor = 1; + best_baud = clk/(clk_div + clk_div/2); + } + else if (baudrate >= clk/(2*clk_div)) + { + *encoded_divisor = 2; + best_baud = clk/(2*clk_div); + } + else + { + /* We divide by 16 to have 3 fractional bits and one bit for rounding */ + divisor = clk*16/clk_div / baudrate; + if (divisor & 1) /* Decide if to round up or down*/ + best_divisor = divisor /2 +1; + else + best_divisor = divisor/2; + if(best_divisor > 0x20000) + best_divisor = 0x1ffff; + best_baud = clk*8/clk_div/best_divisor; + *encoded_divisor = (best_divisor >> 3) | (frac_code[best_divisor & 0x7] << 14); + } + return best_baud; +} +/** + ftdi_convert_baudrate returns nearest supported baud rate to that requested. + Function is only used internally + \internal +*/ +static int ftdi_convert_baudrate(int baudrate, struct ftdi_context *ftdi, + unsigned short *value, unsigned short *index) +{ + int best_baud; + unsigned long encoded_divisor; + + if (baudrate <= 0) { - encoded_divisor = 0; // 3000000 baud + // Return error + return -1; } - else if (encoded_divisor == 0x4001) + +#define H_CLK 120000000 +#define C_CLK 48000000 + if ((ftdi->type == TYPE_2232H) || (ftdi->type == TYPE_4232H) || (ftdi->type == TYPE_232H )) + { + if(baudrate*10 > H_CLK /0x3fff) + { + /* On H Devices, use 12 000 000 Baudrate when possible + We have a 14 bit divisor, a 1 bit divisor switch (10 or 16) + three fractional bits and a 120 MHz clock + Assume AN_120 "Sub-integer divisors between 0 and 2 are not allowed" holds for + DIV/10 CLK too, so /1, /1.5 and /2 can be handled the same*/ + best_baud = ftdi_to_clkbits(baudrate, H_CLK, 10, &encoded_divisor); + encoded_divisor |= 0x20000; /* switch on CLK/10*/ + } + else + best_baud = ftdi_to_clkbits(baudrate, C_CLK, 16, &encoded_divisor); + } + else if ((ftdi->type == TYPE_BM) || (ftdi->type == TYPE_2232C) || (ftdi->type == TYPE_R )) + { + best_baud = ftdi_to_clkbits(baudrate, C_CLK, 16, &encoded_divisor); + } + else { - encoded_divisor = 1; // 2000000 baud (BM only) + best_baud = ftdi_to_clkbits_AM(baudrate, &encoded_divisor); } // Split into "value" and "index" values *value = (unsigned short)(encoded_divisor & 0xFFFF); - if (ftdi->type == TYPE_2232C || ftdi->type == TYPE_2232H || ftdi->type == TYPE_4232H || ftdi->type == TYPE_232H ) + if (ftdi->type == TYPE_2232C || ftdi->type == TYPE_2232H || + ftdi->type == TYPE_4232H || ftdi->type == TYPE_232H ) { *index = (unsigned short)(encoded_divisor >> 8); *index &= 0xFF00; -- 1.7.1