topic Re: I2C Monitor Mode on LPC4088 in LPC Microcontrollers

I2C Monitor Mode on LPC4088

alexanderplanit — Wed, 03 Aug 2016 12:34:07 GMT

Hi,

i want to use the lpc4088 (on the quickstartboard from mbed) as an i2c sniffer. The integrated i2c monitor mode of the lpc4088 would be perfect for my application, but sadly i didn't find a sufficient example to show me how to use this mode.

I read the headerfile i2c_17xx_40xx.h from the lpcopen package (v2.10), but i still couldn't figure out how i can use this.

Are there some examples available that i missed or instructions i could follow?

Thanks in advance for any advice and

BR,

Alex

Re: I2C Monitor Mode on LPC4088

Carlos_Mendoza — Thu, 11 Aug 2016 14:43:07 GMT

Hi Alexander,

We don't have that example but you could use the attached CMSIS example that includes a I2C monitor mode driver as base to create your project.

Hope it helps!

Best Regards,

Carlos Mendoza

Technical Support Engineer

Re: I2C Monitor Mode on LPC4088

alexanderplanit — Wed, 07 Dec 2016 10:24:47 GMT

Hi Carlos,

thanks for the help.

I got my I2C Monitor Mode now up and running, but i ran into another problem.

Apparently my Interface interprets all intercepted I2C-Packets (so everything between Start and Stop Condition) as Writing-Operations (as Slave-Receiver).

Meaning the State changes look like:

0x60 -> 0x80 -> 0x80 -> ... -> 0xA0

where the states indicate the following:

0x60: Own Slave Address + Write Bit received, ACK received

0x80: Addressed with own Slave Address, Data received, ACK returned

0xA0: Stop or Repeated Start received

However they should also be State changes like:

0xA8 -> 0xB8 -> 0xB8 -> ... -> 0xC8 -> 0xA0

where the states indicate the following:

0xA8: Own Slave Address +Read Bit has been received; ACK has been returned

0xB8: Data byte in I2DAT has been transmitted; ACK has been received

0xC8: Last data byte has been transmitted, ACK has been received

I verified the measured protocol with an Logic Analyzer and the Results indicate that the R/W-Bit was indeed transmitted correctly.

Here is the code i used to configure the I2C interface:

LPC_I2Cx(id)->ADR0 = (I2C_SLAVE_ADDR << 1); //Set own device address
LPC_I2Cx(id)->MASK[0] = (I2C_SLAVE_MSK << 1); //Set address mask
LPC_I2Cx(id)->MMCTRL |= I2C_I2MMCTRL_MM_ENA; //Enable I2C Monitor Mode
LPC_I2Cx(id)->CONSET = I2C_CON_I2EN | I2C_CON_AA;
LPC_I2Cx(id)->CONCLR = I2C_CON_STA | I2C_CON_STO | I2C_CON_SI; //Enable I2C Interface

BOTTOM LINE:

So that leaves the Question what causes this behavior?

Is it the I2C Interface itself that forces the R/W Bit to a '0' and interprets therefore a Writing Operation (+ jumping to the corresponding States)?

If YES, is there a way to bypass this Issue?

If NO, did I configure something wrong?

(Feedback/Suggestions/Experiences are much appreciated ;-) )

BR,

Alexander

Re: I2C Monitor Mode on LPC4088

Carlos_Mendoza — Fri, 10 Feb 2017 23:38:20 GMT

Hi Alexander,

Could this be related with the I2C errata?

http://www.nxp.com/documents/errata_sheet/ES_LPC407X_8X.pdf

Best Regards!
Carlos Mendoza
Technical Support Engineer

Re: I2C Monitor Mode on LPC4088

alexanderplanit — Mon, 13 Feb 2017 06:58:25 GMT

Hi Carlos,

I'm afraid not.

The errata sheet describes an issue where the data of an i2c transmission is corrupted, but my interface doesn't enter any i2c-transmitter states in the ISR in the first place.

And i verified with a logic analyser, that there are recieve and transmit operations happening on the Bus.

BR,

Alexander