I2C can not read more than 20 data in one time

[Xbiotec]

hi,
I'm working on I2c with I2C master with TTGO ESP32, I found that transaction read is working well with length (LengthToRead)<=20 if more than 20 not working.

I2C read.jpg (142.09 KiB) Viewed 7232 times

I2CRead.fcfx

(20.38 KiB) Downloaded 674 times

Thx for your prompt reply

[LeighM]

Hi Seb,
The size of the Data buffer needs increasing

Code: Select all

Data[20]

can only hold up to 20 bytes.
This needs to be Data[24] to accept a read of 24 bytes.

[Xbiotec]

Hi,
I put to 20 before to send you to make a test and forget to replace by 24 but even if you increase it to 24 the result will be NG.

[LeighM]

Ah, OK.
Yes, I've just checked the generated code and you are correct.
The I2C Master component is limiting the buffer size to 20 bytes, as passed to the I2C CAL component, and the CAL C then inhibits the transfer of 24 bytes into a 20 byte buffer.
A quick fix would be for you to directly use the I2C CAL component, rather than the I2C Master component (until it gets fixed).
Component Libraries -> Search

[Xbiotec]

ok thx, do you think this could be fixed next week ?

[medelec35]

Hi Seb, it's a balance between how many bytes and how much memory that's used.
If you let me know how many bytes you wish to read, I can increase the buffer size accordingly as a temp measure.

[mnfisher]

A possible easy fix...

In i2c_master:

Code: Select all

MX_UINT16 FCD_005f1_I2C_Master1__Transaction_Read(MX_UINT8 *FCL_BUFFER, MX_UINT16 FCLsz_BUFFER, MX_UINT16 FCL_LENGTH)
{
    //Local variable definitions
    MX_UINT16 FCR_RETVAL;


    // .Return = cal_i2c :: Transaction_Read(.Buffer, .Length)
    FCR_RETVAL = FC_CAL_I2C_Transaction_Read_1(FCL_BUFFER, 20, FCL_LENGTH);   // Change 20 to FCLsz_BUFFER

    return (FCR_RETVAL);
}

The call to i2c::TransactionRead has a size of 20 hardcoded in - this should be FCLsz_BUFFER. This shouldn't affect the memory usage of the library as the buffer is passed by reference - and the user controls how big the buffer is...
The cal_i2c_transaction read returns nothing if length > size of buffer so at present requesting anything >20 bytes will fail...

Martin

[Xbiotec]

Could tell me what should I do ?
I'm not sure to understand.

[mnfisher]

The fix needs to be applied to the component code - so is a fix for Matrix...

However, you can test it...

Try:

I2CReadTest.fcfx

(21.37 KiB) Downloaded 526 times

Note - the call to the macro Read instead of using the component's read..

Martin

[Xbiotec]

it work's thx