S12 / MagniV Microcontrollers中的主题 Re: Bug in Freescale IIC (I2C) example code (AN2318)

Bug in Freescale IIC (I2C) example code (AN2318)

JonHart — Mon, 26 Jun 2006 19:29:37 GMT

FYI:

For anybody trying to get the freescale example AN2318 IIC code to work.

The code works fine if you tx or rx 2 bytes or more.

If you rx a single byte, however, the code fails to switch off master transmission acknowledgements ( by setting TXAK = 1). This is because it relies on the transmission of the "last but one" byte to switch TXAK off. Of course if you are only rx'ing one byte their is no "last but one" byte.

This problem occurred for me because the AD5242 digital pot I am using requires the reception of a single byte (after the slave address). The read worked for the majority of the time, but occasionally resulted in the failure of the device to deassert the SDA line. The failure occured on the next read/write when the bus was still busy.

Re: Bug in Freescale IIC (I2C) example code (AN2318)

JonHart — Mon, 26 Jun 2006 19:31:43 GMT

...oh and my solution!

Check the number of bytes. If it is only one, set TXAK when you send the IIC START signal.

Re: Bug in Freescale IIC (I2C) example code (AN2318)

DrSeuss — Tue, 27 Jun 2006 06:38:25 GMT

I think you are correct. I will try to get the AN updated.

Thank you.

Re: Bug in Freescale IIC (I2C) example code (AN2318)

Selea — Thu, 08 Aug 2013 12:46:12 GMT

to me it doesn't work anyway with 1 byte read... I have a 10th clk after the ack one, so it doesn't make the stop condition...