Wrong data on I2C 2 ?

[antonius]

Dear Members,

I got a wrong data on I2C 2 for LCD, the first time it was ok, after a while it becomes like in the photo, what do you think the cause of it ?

I have put a pull up resistor for it 10K, and the speed is 100KHz,

I2C1 for Accelerometer and temperature,

Is it because of power supply or something else ?

Thanks

[Tesla DeLorean]

As I recall you have an IO Extender, with 4-bit connectivity, I'd suppose the two halves aren't getting cleanly latched.

Perhaps review with a logic analyzer, and review setup/hold timing requirements of the display.

[antonius]

............. I'd suppose the two halves aren't getting cleanly latched....

do you mean between expander and the LCD ?

[antonius]

I reduced SCL to 50KHz, still got the same response, after GPS is on or accelerometer is on...

[Tesla DeLorean]

Ok, so you've established that the speed of the I2C interface isn't the issue. Now you need to review the performance of the signals to the display's micro-controller, and how the edges/transitions of those relate.

[antonius]

when I make time out =100ms

HAL_I2C_Master_Transmit (&hi2c2, 0x7E,(uint8_t *) data_t, 4, 100);

it's reducing the error, is it the cause or something else ..?

[Tesla DeLorean]

Do the functions return an error status? The timeout would need to be accommodative of the amount of data you plan to transmit, and the bus speeds you are clocking at.​

[antonius]

I reduced SCL to 40KHz, it's now stablizing,

 hi2c2.Init.ClockSpeed = 40000;

I keep posted, perhaps, I need to reduce the clock lower ....Iet's see...