Hello all!
I'm trying with no success to use the RTS handshaking signal on a 232R
device
(http://www.ftdichip.com/Products/EvaluationKits/TTL-232R-3V3.htm)
My setup involves transmitting (with another PC and a similar USB-serial
adapter) at a fast pace random
characters to the RX pin of the above device, which is read every second
by my program reader.c (see attachment)
Under these circumstances I expect the hardware RX buffer of the chip to
quickly fill up, and
if the hardware handshaking signals work correctly, then the chip should
shout "hey my RX buffer is
full, don't send me any more data!" by toggling RTS to logic 0 aka 0
Volts (remember RTS# pin on FTDI
232R chips is active low)
However, RTS logic value measured with a multimeter sits constantly at
3.3V, no matter how long I wait.
Any ideas? Help/suggestions would be really appreciated as I tried to
debug this problem in many ways with no luck...
Cheers,
Luca
As an aside, I found a list of commands accepted by 232R chips
(http://yosemitefoothills.com/Electronics/FTDI_Chip_Commands.html)
and tried to modify libftdi (with no difference on the above described
RTS pin behavior) as follows
int ftdi_setflowctrl(struct ftdi_context *ftdi, int flowctrl)
{
////original
//if (usb_control_msg(ftdi->usb_dev, SIO_SET_FLOW_CTRL_REQUEST_TYPE,
//SIO_SET_FLOW_CTRL_REQUEST, 0, (flowctrl |
ftdi->index),
//NULL, 0, ftdi->usb_write_timeout) != 0)
// ftdi_error_return(-1, "set flow control failed");
//return 0;
////modified by me: see if it's a problem related to libftdi not
// properly activating handshaking signals on both RX and TX
// sections of 232R chips.....
if (usb_control_msg(ftdi->usb_dev, SIO_SET_FLOW_CTRL_REQUEST_TYPE,
SIO_SET_FLOW_CTRL_REQUEST, 0, (flowctrl |
ftdi->index),
NULL, 0, ftdi->usb_write_timeout) != 0)
ftdi_error_return(-1, "set flow control failed");
if (usb_control_msg(ftdi->usb_dev, SIO_SET_FLOW_CTRL_REQUEST_TYPE,
0x01, 0, 0x10 ,
NULL, 0, ftdi->usb_write_timeout) != 0)
ftdi_error_return(-1, "set flow control failed");
if (usb_control_msg(ftdi->usb_dev, SIO_SET_FLOW_CTRL_REQUEST_TYPE,
0x01, 0, 0x11 ,
NULL, 0, ftdi->usb_write_timeout) != 0)
ftdi_error_return(-1, "set flow control failed");
printf("\n\n Modified libFTDI\n\n");
return 0;
}
--
libftdi - see http://www.intra2net.com/en/developer/libftdi for details.
To unsubscribe send a mail to libftdi+unsubscribe@xxxxxxxxxxxxxxxxxxxxxxx //
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2 as
// published by the Free Software Foundation.
//
// readwrite.c Copyright (c) 2009 Luca Mannatrizio
<ltrizio@xxxxxxxxxxxxx>
//
//
//---------------------------------------------------------------------------------
//
// COMPILE ARGUMENTS
//
// compile with the following
// gcc -O receiver.c -o receiver /usr/local/lib/libftdi.a -W -Wall -Wformat
/usr/lib/libusb.a
//
//---------------------------------------------------------------------------------
//
// NOTES
//
// To avoid the need to be root to run the program just setup permissions for
your
// FTDI device in /etc/udev/rules.d
//
// Within file 40-permission.rules add the following line
//
// SYSFS{idVendor}=="0403", SYSFS{idProduct}=="6001" GROUP="whatever group
you are in"
//
// for example plugdev and then add yourself (if not already done) to the
plugdev group
//
// libftdi-0.15 does this already to allow any members of the plugdev group to
access FTDI devices
//
//---------------------------------------------------------------------------------
//
// PROBLEMS TO SOLVE
//
//
// 1. RTS hanshaking signal misbehaves after setting hardware flow control.
//
//
// FTDI documentation reports the following:
//
// *. RTS# and CTS# are by factory setting active low (hence the reason for
character #) unless eeprom of
// FTDI chip has been set to the contrary. I checked my FTDI device is
configured with factory settings.
//
// *. RTS# is an output from FTDI device that controls flow of data into FTDI
RX pin
// 0: whatever device attached to FDTI device can transmit
// 1: whatever device attached to FDTI device should stop transmitting
//
// *. CTS# is an input to FTDI device that controls the flow of data out of
FTDI TX pin
// 0: FTDI device can send data
// 1: FTDI device cannot send data
//
//
// The RX pin of the device which this program runs upon is driven externally
and filled with random data
// at a pace faster than this program polls the device.
// As a result I expect the hardware RX buffer of the chip which this program
runs upon to quickly fill up
// If the hardware handshaking signals work correctly, then the chip should
shout "hey my RX buffer is full, don't send me any more data!"
// by toggling RTS to logic 0 aka 0 Volts (remember RTS# pin on FTDI chips is
active low)
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/unistd.h>
#include <pthread.h>
#include <getopt.h>
#include "ftdi.h"
#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
struct ftdi_context ctx;
static void Error(const char *where,int rv,struct ftdi_context *ctx,int doclose)
{
if(rv)
{
fprintf(stderr,"%s: rv=%d, error=%s, errno=%s (%d)\n",
where,rv,ctx->error_str,strerror(errno),errno);
if(doclose)
{
rv=ftdi_usb_close(ctx);
fprintf(stderr,"close: rv=%d, error=%s, errno=%s
(%d)\n",
rv,ctx->error_str,strerror(errno),errno);
}
ftdi_deinit(ctx);
exit(1);
}
else
fprintf(stderr,"%s: OK\n",where);
}
////////////////////////////////////////////////////////////
//
// Main
//
int main() {
int i;
int rv;
int vendor = 0x0403;
int device = 0x6001;
const int bufsize = 16;
unsigned char buf[bufsize];
// Initialize
rv=ftdi_init(&ctx);
Error("init",rv,&ctx,0);
// Open FTDI device by its serial
rv=ftdi_usb_open_desc(&ctx, vendor, device, NULL , "FTCY0SGG");
// Open first FTDI device encountered
//rv=ftdi_usb_open_desc(&ctx, vendor, device, NULL , NULL);
Error("open",rv,&ctx,0);
// Reset
rv=ftdi_usb_reset(&ctx);
Error("reset",rv,&ctx,1);
// Disable bitbang
rv=ftdi_disable_bitbang(&ctx);
Error("bitbang is OFF",rv,&ctx,1);
//rv=ftdi_enable_bitbang(&ctx, 1<<0x02);
//Error("bitbang is ON",rv,&ctx,1);
// Set baudrate to 115200
rv=ftdi_set_baudrate(&ctx,115200);
Error("set baudrate to 115200",rv,&ctx,1);
// Set hardware flow control
rv=ftdi_setflowctrl(&ctx,SIO_RTS_CTS_HS);
Error("set hardware flow control",rv,&ctx,1);
// Set software flow control
//rv=ftdi_setflowctrl(&ctx,SIO_XON_XOFF_HS);
//Error("set software flow control",rv,&ctx,1);
printf("\n\n\nReading (in main with no threads) from device FTCY0SGG");
while ( 1 )
{
rv=ftdi_read_data(&ctx,buf,bufsize);
if(rv<0) Error("read",rv,&ctx,1);
else
{
printf("%3d: ",rv);
for(i=0; i<rv; i++)
printf("%02x%s",buf[i],i%8==7 ? i%16==15 ? "\n " : " " : " ");
}
printf("\n"); fflush(stdout);
sleep(1);
}
}
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