I2C Reading frequency

Question

I am currently working on a project that use the ftdi MPSSE (FT232H) with an I2C sensor.

I did manage to connect and read the value, I want to read them faster.

Currently I read that at nearly 10hz, and it is very slow. I know fore sure that I can read them faster because I used to work on other I2C sensor and I could read them till 3KHz.

I don't know where the problem is.

I try to use different "option" acknowledge, start bit, stop bit etc, but I can't find any solution.

The weird thing is : if I use an Arduino board I can read them much much faster (1khz).

But for purpose I am block with this ftdi chip.

Code is here.

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>

/* OS specific libraries */

#include<windows.h>


#include "ftd2xx.h"
#include "libMPSSE_i2c.h"
#define I2C_DEVICE_BUFFER_SIZE          256
static uint8 buffer[I2C_DEVICE_BUFFER_SIZE] = { 0 };


int main(int argc, char* argv[])
{
    uint32 adresse = 0x54;
    uint8  data[7];
    uint32 datatoread = 7;
    uint32 datatoread2 = 7;
    uint8  data2[7];
    uint32 numberofbytesread = 0;
    int i = 0;

    Init_libMPSSE();

    FT_STATUS status;
    FT_DEVICE_LIST_INFO_NODE channelInfo;
    FT_HANDLE handle;
    uint32 channelCount = 0;
    uint32 datashort = 0;
    //buffer[datatoread];

    status = I2C_GetNumChannels(&channelCount);
    if (status != FT_OK)
        printf("Error while checking the number of mpsse channel");
    else if (channelCount < 1)
        printf("erro no MPSE channels are available");

    printf("there are %u channel available \n\n", channelCount);

    // Print out details of each mpsse channel 

    for (uint8 i = 0; i < channelCount; i++) {
        status = I2C_GetChannelInfo(i, &channelInfo);
        if (status != FT_OK)
            printf("Error while checking the number of mpsse channel");

        printf("Channel number : %d\n", i);
        printf("description : %s\n", channelInfo.Description);
        printf("Serial number : %s\n", channelInfo.SerialNumber);
    }
    //ask the user to select a channel
    uint32 channel = 0;
    printf("\nenter a channel to use : ");
    scanf_s("%d", &channel);

    // open the I2C channel 

    status = I2C_OpenChannel(channel, &handle);
    if (status != FT_OK)
        printf("error while oppening the mpsse channel");

    //init the channel

    ChannelConfig I2C_ChannelConfig;
    I2C_ChannelConfig.ClockRate = I2C_CLOCK_FAST_MODE;
    I2C_ChannelConfig.LatencyTimer = 1; // 1mS latency timer
    I2C_ChannelConfig.Options = 0;
    //uint32 mode = I2C_TRANSFER_OPTIONS_START_BIT | I2C_TRANSFER_OPTIONS_STOP_BIT;
    
    
    status = I2C_InitChannel(handle, &I2C_ChannelConfig);
    if (status != FT_OK)
        printf("error while oppening the mpsse channel");

       while (1) {
        //i++;
        
        status = I2C_DeviceRead(handle, adresse, datatoread, data, &numberofbytesread, I2C_TRANSFER_OPTIONS_START_BIT | I2C_TRANSFER_OPTIONS_NACK_LAST_BYTE);
        //printf("\n%d",i);
        datashort = (data[3] << 8) + data[2];
        printf("\nForce is  : %u DaN", datashort);
        //Sleep(1);
        //getchar();
    }

    I2C_CloseChannel(handle);
    Cleanup_libMPSSE();
    //getchar();
    return 0;
}

Thanks.

Use your oscilloscope to watch the I²C communication, and then edit your question and add your findings. — the busybee
– the busybee, Commented Jun 22, 2022 at 14:21
printf() is useful for debugging, but does add latency when wanting to do something in a fast loop. Once you have the O'scope connected, consider removing the printfs — ryyker
– ryyker, Commented Jun 22, 2022 at 14:24
I'm using a FTDI converter as well, the model is UM232H. But I am not being able to get to the I2C sensor which in this case is an accelerometer. How did you manage to get data? — Escris
– Escris, Commented May 4, 2023 at 8:25
in wich environment do you work ? For your information, they released new libraries but there is currently a problem with them. So you should use the 0.6 and not the 0.3 — Harith 75
– Harith 75, Commented May 5, 2023 at 9:02

mgmussi · Accepted Answer · 2022-06-22 14:23:15Z

1

You are configuring your I2C_ChannelConfig.ClockRate to I2C_CLOCK_FAST_MODE (400kb/sec), but you can use I2C_CLOCK_FAST_MODE_PLUS (1000kb/sec) or I2C_CLOCK_HIGH_SPEED_MODE (3.4Mb/sec).

answered Jun 22, 2022 at 14:23

mgmussi

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3 Comments

Harith 75 Over a year ago

Hi thank for you answer l already try it but it does not change the speed. I think the problem come from the reading part. Because when I change the argument option, it does change the result of the speed but for example when I set the option with just a START bit the result as return is 65535. It's pretty weird. I2C_DeviceRead(FT_HANDLE handle, uint32 deviceAddress, uint32 sizeToTransfer, uint8 *buffer, uint32 *sizeTransferred, uint32 options). I guess l'll have to check that with a scope

mgmussi Over a year ago

Maybe try adding I2C_TRANSFER_OPTIONS_FAST_TRANSFER to your options and see if it helps (I2C_TRANSFER_OPTIONS_START_BIT | I2C_TRANSFER_OPTIONS_NACK_LAST_BYTE | I2C_TRANSFER_OPTIONS_FAST_TRANSFER).

Harith 75 Over a year ago

it says "if I2C_TRANSFER_OPTION_FAST_TRANSFER is set then setting this bit would mean that the address field should be ignored. The address is either a part of the data or this is a special I2C frame that doesn't require an address*/" I do need my adress. I sent a message to the technical support of ftdi. Thanks

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