hi chris, you're in fairly tricky territory here.
yes, you need to switch bus modes; see any application or driver (hint: the sd driver does!) that uses spi to understand how to wire in usartcontrol to do what you want.
you're on the right track, but there are a couple of really important things that you should note first. since the msp430 shares one pin that conducts traffic in i2c (sda) and spi modes (simo), and the clock pin, you'll need to disable the card itself, or it will think that you're talking to it when you ask the magnetometer for data.
if you follow the calls inside the fatfs module to their implementations (diskio layer) you'll find what you need to bring the card up and down while you pull data from the magnetometer. so, you can use the calls that the filesystem uses. you might also try just doing the lowest-level things in the card disable/enable functions.
you'll also need to consider the timing; writing one disk block takes about 14 ms, so if you're reading the magnetometer at 10hz, then you'll have to slip the (relatively infrequent) disk writes in during the 72 ms that it's idle between samples. sounds easy, but notice that the driver has to pause during start-up for a power cycle (longer than sd spec, but we found that not all cards meet that spec).
i hope that this helps. have fun, steve On 06/14/2011 03:02 PM, Chris B wrote:
Deal all, I am trying to enable SD card logging of timestamp, accelerometer, gyro and magnetometer data on the Shimmer2r + Kinematics board. I'm getting a bit stuck on enabling SD logging of the magnetometer data. To start with, I have essentially extended the Shimmer HostTimeLogging app. I am aware that the Magnetometer and SD card access utilise the same bus USART0, thus i need to switch USART0 between the Magnetometer (I2C mode) and the SD card access (SPI mode) in a timely manner. This seems straightforward for the Magnetometer, i just use calls to Magnetometer.enableBus() or Magnetometer.disableBus(). However, I can't figure out which commands I should be using for the SD card access. I'm not sure whether those within the FatFs interface such as FatFs.mount() and FatFs.unmount() are the correct calls to make in this instance, looking at the lower-level code, they seem to do more than just set up the bus mode. I think i should be using calls such as Usart.setModeSpi(config) but am unsure how to expose these function in the top level code in a safe manner alongside FatFs. Any help on this would be appreciated. regards Chris _______________________________________________ Shimmer-users mailing list [email protected] https://lists.eecs.harvard.edu/mailman/listinfo/shimmer-users
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