Maximum console uart baud rate in Iotdk board

[ericwu13]

Issue Summary

• Type: Question
• Category: Usability
• Priority: Urgent
• Release Version: Specified version such as 2016.05 or All

• BOARD IoTdk

  Question

  the default baudrate is 115200. However, I want a faster baudrate. I set it to 230400 up to 921600. But none of them work. But I can set it to 38400, and my computer serial works. Is it possible to use the console uart baudrate up to 1M? thanks.

PS: I set the baudrate in iotdk.h file like the below.

#define BOARD_CONSOLE_UART_BAUD         UART_BAUDRATE_921600

[ericwu13]

Hi, is there any comments about it? Thanks!

[IRISZZW]

baud rate = (serial clock frequency)/(16×divisor), and serial clock frequency is 16MHz in itodk board. so divisor = 10000000/baud rate. when baud rate is high, then divisor will be inaccuracy.

[ericwu13]

So, is it possible to configure a higher baud rate other than 115200 (e.g. 1M)? If I should change the divisor register in Iotdk, how should I do it? I want a faster serial transmission. Thanks!

[jelly99709]

I also encounter the baud rate problem. What should I do to change the divisor value in iotdk to have higher baud rate?

[ericwu13]

Hi, sorry for keeping asking. Is there really no methods to accelerate the baud rate to 1M? I'm using camera module and can generate images with extremely low fps on my laptop. Therefore, I really need a solution for it to have a higher fps for camera module, but I can't find any... There's little documentation talking about this board. Can you help us on this? Thanks.

[IRISZZW]

#define BOARD_CONSOLE_UART_BAUD 1500000 //(iotdk.h)

/** convert uart baudrate to subsystem divisor */
#define SS_UART_BAUD2DIV(perifreq, baud)        ((perifreq) / ((baud)*16) + 1)
Inline int32_t set_baud(SS_UART_DEV_CONTEXT *ctx, uint32_t baud)
{
    uint32_t param;
    DEV_UART_INFO *info = ctx->info;

    param = SS_UART_BAUD2DIV(ctx->bus_freq, baud); //param=1 when baud = 1500000
    io_uart_ioctl(ctx->dev_id, IO_UART_SET_DLx, &param);
    info->baudrate = baud;

    return E_OK;
}

when you set BOARD_CONSOLE_UART_BAUD = 1500000, you will get the 1000000 baudrate.

[ericwu13]

why there exists such a difference? Shouldn't we set the baud rate to 1M if we want 1M baud rate? I tried to calculate the divisor value when baud rate = 1.5M and 1M, which are 0.67 and 0.99 respectively. These are different divisor values though. Could you elaborate on how it works? Thanks

[IRISZZW]

the divisor values should be integer, we round up the divisor values. #define SS_UART_BAUD2DIV(perifreq, baud) ((perifreq) / ((baud)*16) + 1)

[ericwu13]

oh, so we need divisor = 1, so basically, we can also set baud rate to 1300000 with which we can get divisor value = 1?

[IRISZZW]

yes, because serial clock frequency is 16MHz, so the max baudrate is 1000000 when divisor = 1.

[ericwu13]

Thanks. It works!!! I finally understand how to control it. Really appreciate for your help. I'm closing this.