LP-AM243: UART support for 2 M baud

Hi Dinesh,

The UART documentation mentions the driver is currently contrained to UART 16x mode (<= 115.2 Kbaud/s), please see: https://software-dl.ti.com/mcu-plus-sdk/esd/AM243X/08_01_00_36/exports/docs/api_guide_am243x/DRIVERS_UART_PAGE.html

Nevertheless, the Sysconfig parameters for the UART can be set for 2 Mbaud as follows:

• Set operational mode to 13x
• Set Baudrate to 2000000

The UART hardware supports three modes of operation, please see the AM64x/AM243x TRM (spruim2c.pdf), 12.1.5.2.1.3 UART Protocol and Data Format.

For 2 Mbaud, the mode must be set to 13x oversampling.

It should be possible to select a 192/96/64/48 MHz or 160 MHz UART functional clock (FCLK). Please see TRM:

• 5.1.1.3.1.5 Clock Muxing and Division Registers
• Table 5-651. CTRLMMR_USART0_CLK_CTRL Register Field Descriptions
• Table 5-665. CTRLMMR_USART0_CLKSEL Register Field Descriptions

FCLK is further divided by the UART Divisor (DLH:DLL registers).

The final baud rate will be FCLK/Divisor/13, which may not be exactly 2 Mbaud, i.e. there will be some error in the baud rate.

I'm able to change FCLK supplied to the UART by changing the Sysconfig setting for "Clock Freq", but the UART driver internal clock is fixed at 48 MHz. I need to review this with the software development team to see if I'm missing something. I'll keep you posted.

Regards,
Frank

Dinesh,

The UART driver documentation is incorrect ("UART 16x mode (<= 115.2 Kbaud/s)"), and 13x mode is supported.

Regards,
Frank