Content originally posted in LPCWare by nidalpres on Fri Apr 03 19:46:58 MST 2015 I have a C++ project which has a cpp file with a function that goes like this:
void I2C_Init()
{
/* Initialize I2C
* - enable I2C clock via SYSAHBCLKCTRL
* - resets I2C peripheral via clocking I2C pin in PRESETCTRL
*/
Chip_I2CM_Init(LPC_I2C);
/*
* Sets SCLH and SCLL based on PCLK (which is same as core clock)
* and given speed
*/
Chip_I2CM_SetBusSpeed(LPC_I2C, SPEED_100KHZ);
/*
* Clears SI, STO, STA and AA bits
* via CONCLR
*/
Chip_I2CM_ResetControl(LPC_I2C);
/*
* clears I2EN bit via CONCLR
* Chip_I2CM_SendStart() will set I2EN bit
*/
Chip_I2CM_Disable(LPC_I2C);
}
It works like a charm, I2C initializes and I can communicate with my I2C device.
If I change it to this (note how instead passing LPC_I2C to functions I pass a variable with that value):
all I get after calling Chip_I2CM_XferBlocking() (or anything else for that matter) is xfer.status == I2CM_STATUS_BUS_ERROR.
Also, weird, in second case (when using variable), LPCXpresso IDE reports connection error when uploading code to target (via debug in LPCXpresso IDE). I have to disconnect LPCXpresso 1347 board from USB, connect it back again and uploading code now works.
Also, weird, in second case (when using variable), if I set breakpoint on my call to Chip_I2CM_XferBlocking() and then just press F8 (continue run) when execution hits the breakpoint, suddenly there are no more I2CM_STATUS_BUS_ERRORs and I get readouts from the sensor connected to LPCXpresso 1347 board.
Remove variable lpcI2C and pass LPC_I2C value directly to those calls in I2C_Init(), and all works fantastically from the start, no need to reset board by reconnecting it, code upload works right away, code reads data from sensor from the start.
My question: W. T. F. ???
Excuse my french, I just spent like 3 hours figuring out what is going on and at the end narrowed it down to what I described in here. Now I'm just puzzled, amazed and bewildered.
Content originally posted in LPCWare by nidalpres on Fri Apr 03 19:49:34 MST 2015 Btw. those code samples are not code samples, both of those I2C_Init() functions are literally the way I pasted them in that post.
