[Tinyos-help] Problem with I2CPacket.read(...) in Atm128I2CMasterC for Iris and Mica platforms

[Philip Levis]

On Jun 2, 2008, at 1:18 PM, Christopher Leung wrote:

> This is just a heads-up about the I2CPacket.read(i2c_flags_t flags,  
> uint16_t addr, uint8_t length, uint8_t* data) function in the  
> Atm128I2CMasterC component.
>
> To read n bytes from a slave, the parameter length must be set to (n 
> +1). In the returned function, async event void readDone(error_t  
> error, uint16_t addr, uint8_t length, uint8_t* data), the first  
> bytes read will be in data[1]; second byte in data[2] and so on. The  
> byte in data[0] will contain the slave address and the R/notW bit.
>
> I don't know if that was done on purpose as I couldn't find any of  
> that mentionned in the comments.
>
> If someone does want to fix this, the source of the problem is in  
> the Atm128I2CMasterPacketP component (I have version 1.7 2007/11/01  
> 18:10:36 fredjiang Exp). More specifically, in the  
> I2C.commandComplete() function. The problem is that the index value  
> is incremented before the first byte is read from the slave.  
> Therefore, at line 260 when the contents of the Two-Wire-Interface  
> buffer is read and stored, the function is actually storing the byte  
> it last sent. That is, it is reading the address and the R/notW bit  
> it just wrote onto the I2C bus.

Can you send a patch to the list?

Phil