stm32H503RB Determination of I3C IBI payload size

[Hexu]

Hi,

I am using the nucleo-H503RB I3C (Controller mode) with this example to connect to an I3C standard chip. The sensor transmits IBI with 5 bits of payload but I noticed that the STM32 receives only 4 bits, and then it stops receiving the fifth bit.

Is there any method I can define the receive IBI payload size on the controller side? Any kind of help is appreciated. 🙂

[Foued_KH]

Hello @Hexu , 

The maximum (static) payload data size is given by IBIP[2:0] in the I3C_MAXRLR register. it can be 1, 2, 3 or 4 bytes.

Br,
Foued

[Hexu]

Hi @Foued_KH 

Thanks for your kind reply, please forgive me that I am a beginner using the STM series. Just want to ask a dumb question: How can I modify I3C_MAXRLR register? I tried to modify those definitions and I still received 4 bytes of IBI payload.

[Foued_KH · Accepted solution]

The maximum IBI payload data is 4 bytes.

I3C maximum read length register (I3C_MAXRLR) : 
IBIP[2:0]: IBI payload data maximum size, in bytes (when I3C acts as target)
000: null payload data size (only allowed when BCR2 = 0 in the IC3_BCR register)
001: 1 byte (mandatory data byte MDB[7:0]
010: 2 bytes (including first MDB[7:0])
011: 3 bytes (including first MDB[7:0])
100: 4 bytes (including first MDB[7:0])
others: same as 100

Foued