[ECOS] Correction of baudrate calculation for QUICC SMC uart

[ECOS] Correction of baudrate calculation for QUICC SMC uart

[Tord Andersson]

Hi,

When using higher baudrates in an MPC823e based system using eCos and
the SMC UART, I found that the baudrate was slightly wrong. I checked
the baudrate calculation and believe that it could be somewhat altered. 
The change has solved our problem. 
Below is the result of "diff -u -5 -b -p" between the original and the
patched file for review.
The file is located in
.../packages/devs/serial/powerpc/quicc/current/src

---------------------------------------

--- quicc_smc_serial.h	Thu Sep  4 08:50:14 2003
+++ patched_quicc_smc_serial.h	Thu Sep  4 09:04:26 2003
@@ -130,8 +130,8 @@
     0,      // 230400
 };
 
-#define UART_BITRATE(n)
(((CYGHWR_HAL_POWERPC_BOARD_SPEED*1000000)/16)/n)
-#define UART_SLOW_BITRATE(n)
((CYGHWR_HAL_POWERPC_BOARD_SPEED*1000000)/n))
+#define UART_BITRATE(n)
((((CYGHWR_HAL_POWERPC_BOARD_SPEED*1000000)/16)/n)-1)
+#define UART_SLOW_BITRATE(n)
(((CYGHWR_HAL_POWERPC_BOARD_SPEED*1000000)/n))-1)
 
 // Channel type select
 #define _SCC_CHAN 0

--------------------------------------

Kind regards,

Tord Andersson
Combitech Systems AB


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Re: [ECOS] Correction of baudrate calculation for QUICC SMC uart

[Gary Thomas]

On Mon, 2003-09-08 at 00:58, Tord Andersson wrote:
> Hi,
> 
> When using higher baudrates in an MPC823e based system using eCos and
> the SMC UART, I found that the baudrate was slightly wrong. I checked
> the baudrate calculation and believe that it could be somewhat altered. 
> The change has solved our problem. 
> Below is the result of "diff -u -5 -b -p" between the original and the
> patched file for review.
> The file is located in
> .../packages/devs/serial/powerpc/quicc/current/src
> 
> ---------------------------------------
> 
> --- quicc_smc_serial.h	Thu Sep  4 08:50:14 2003
> +++ patched_quicc_smc_serial.h	Thu Sep  4 09:04:26 2003
> @@ -130,8 +130,8 @@
>      0,      // 230400
>  };
>  
> -#define UART_BITRATE(n)
> (((CYGHWR_HAL_POWERPC_BOARD_SPEED*1000000)/16)/n)
> -#define UART_SLOW_BITRATE(n)
> ((CYGHWR_HAL_POWERPC_BOARD_SPEED*1000000)/n))
> +#define UART_BITRATE(n)
> ((((CYGHWR_HAL_POWERPC_BOARD_SPEED*1000000)/16)/n)-1)
> +#define UART_SLOW_BITRATE(n)
> (((CYGHWR_HAL_POWERPC_BOARD_SPEED*1000000)/n))-1)
>  
>  // Channel type select
>  #define _SCC_CHAN 0
> 
> --------------------------------------

Yes, it does look like you are correct.  I'll make these changes.

Thanks.

-- 
Gary Thomas <gary@mlbassoc.com>
MLB Associates


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