SDHC + MSP430F1611

[Michael (Gast)]

Hello,
Is the MSP430F1611 good enough to work with a SD HC card and to write on 
it. It has lot of RAM (10KB) which sounds great but is the 8Mhz 
frequency enough to write on the memory card and convert analog signals 
(3 channels, 12-bit @ 20kHz) at the same time?

Thank you!
Michael

[Obelix (Gast)]

3 channels, 12 bit, 20KHz ->
3  2Byte  20000 -> 120kByte/s -> 960kBit/s + overhead

[Christian R. (supachris)]

You shoud use a newer MSP430 with 16 MIPS speed and DMA. The ammount of 
RAM isn´t the critical in your application. With proper use of the three 
DMA-Channels and the timers I think, you can reach your sample rate. But 
before you should figure out, which data rate is possible with the SD 
Card in SPI connection.

[Michael (Gast)]

OK thank you for all these informations.

I'm choosing the MSP430F2617 with DMA and 8KB RAM.
SD card writing speed through the SPI is in theory 25MB/s max. so the 
input clock would be 25Mhz. In our case, the input clock would be 16Mhz. 
It will now depend on the software which has to be optimized to reach 
120kByte/s

[holger (Gast)]

>It will now depend on the software which has to be optimized to reach
>120kByte/s

It depends on the software AND THE CARD to reach 120kByte/s !

[Christian R. (supachris)]

Especially the busy time after writing a data block should be carefully 
evaluated....from manufacturer to manufacturer this time may very 
different...

[holger (Gast)]

>Especially the busy time after writing a data block should be carefully
>evaluated....from manufacturer to manufacturer this time may very
>different...

And this time may vary from block to block !

[Michael (Gast)]

Yes and they don't provide the numbers so easily in the datasheet...

Otherwise, any solution(s) on how to use the SD card bus mode (4-pins) 
which is theoretically 4x faster ?

Or would a uCtrl with a 25Mhz clock be better?

Thanks!

[Christian R. (supachris)]

Michael wrote:
> Yes and they don't provide the numbers so easily in the datasheet...
>
> Otherwise, any solution(s) on how to use the SD card bus mode (4-pins)
> which is theoretically 4x faster ?

If you find the information? This is theoretically closed souce, I 
think.

> Or would a uCtrl with a 25Mhz clock be better?

No, we use a DSP with max. 75MHz SPI clock and have the most of time 
wait for end of busy....