How to configure the UART work in 384K bits/s Baudrate on AM335x

Yaoming Qin

Hi Champ,

My customer needs the UART work in 384K bits/s Baudrate on AM335x, which is the requirement from one sensor communication.

According to the TRM, 19.3.8 Protocol Formatting, UART 16x mode (≤230.4 Kbits/s), UART16x ≤460Kbits/s if MDR3[1] is set.

According to the description for MOD3, when MOD3[1] is set, the FREQ_SEL is necessary to do the configuration as well.

For the FREQ_SEL, it is configured for the sample per bit, but I didn't find any description for the "sample per bit" here.

So could you help to supply on what is the sample here?

Yaoming

Thanks!

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Yaoming,

The UART baud rate is calculated from the formula:

Baud Rate = Input Clock Frequency / (Divisor * Oversampling), or 384kHz = 48MHz / (Divisor * (16 or 13))

So your divisor value will be either 7.81 for 16x Oversampling or 9,62 for 13x Oversampling. As divisor values cannot be fractional numbers, you will have to choose either 8 for 16x Oversampling or 10 for 13x Oversampling. This will give a bit error of 2.4% for divisor value of 8 at 16x Oversampling, or 3.9% for divisor value of 10 at 13x Oversampling.

0 Yaoming Qin over 12 years ago in reply to Biser Gatchev-XID

TI__Expert 3280 points

Hi Gatchev,

Thanks for your detailed reply!

How about the FREQ_SEL? According to the description for MOD3, when MOD3[1] is set, the FREQ_SEL is necessary to do the configuration as well.

Regards!

yaoming

0 Biser Gatchev-XID over 12 years ago in reply to Yaoming Qin

TI__Guru**** 393215 points

Hi Yaoming,

All the necessary configuration for UART mode is described in TRM section 19.3.8.1. I think what you are looking at is used for other modes. In UART mode there are only 16 or 13 samples per bit.

0 Yaoming Qin over 12 years ago in reply to Biser Gatchev-XID

TI__Expert 3280 points

Hi Gatchev,

Thanks for your comment!

BR,

Yaoming

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How to configure the UART work in 384K bits/s Baudrate on AM335x