Dump memory contents of an I2C device

May 2008

I wanted to load my own macros into the NRLink-Nx sensor from mindsensors.com. The first challenge was to understand how to send and receive I2C messages. Then I had to understand the register layout on the NRLink. It turns out that it is pretty simple; if you send an I2C message to write to a particular location then you can update the macros stored in the NRLink EEPROM. The RobotC sendI2CMsg() function writes the bytes into the NRLink EEPROM.

As a test program I wanted to dump out the contents of the EEPROM, so I modified the sample code provided by mindsensors and created this EEPROM RAM dump utility. A couple of features:

•The NRLink is connected on Sensor 1 input.
•The NRLink registers are memory-mapped and so appear as 256 bytes that can be read written to using I2C messages.
•The SensorType must be set to sensorI2CCustom9V. If you set it to sensorI2CCustomFast9V then I got a lot of ERR_COMM_BUS_ERR (-35) errors. They seem to occur intermittently and it must be related to the device speed on the I2C bus.
•The program will read the full 256 bytes of addressable register space and then create a file on the NXT named testFile.dat. The bytes are written into the file sequentially. You can then upload this file in RobotC IDE to your PC and view it in a hex editor.
•I also wrote a function to display the register contents on the screen; you can display a range of addresses and also it will print both the hex value and ASCII character at the address.

The I2CMemoryDump.c is reproduced below, and tested in RobotC 1.22 beta with NXT firmware 7.35.

The function that dumps the I2C memory address space to a file is dumpNRLinkRAM(). It iterates through the I2C address space and writes the memory contents into a file on the NXT named testFile.dat.

//*!!Sensor, S1, NRLINK, sensorI2CCustomStd9V, , !!*//

//*!! !!*//

//*!!Start automatically generated configuration code. !!*//

const tSensors NRLINK = (tSensors) S1; //sensorI2CCustomStd9V //*!!!!*//

//*!!CLICK to edit 'wizard' created sensor & motor configuration. !!*//

* Dump the contents of the EEPROM in the mindsensors NRLINK

* sensor and record them to a data log file and print on the screen

* Use this program to debug writing macros into the NRLink-Nx device

* Modified by Mark Crosbie mark@mastincrosbie.com 1 April 2008

* To install macros that power both motors simultaneously

* For more information visit http://markclego.mastincrosbie.com

* Original code written by Dr. Nitin Patil

* Copyright (c) mindsensors.com 2006, 2007

* for more info visit www.mindsensors.com

//definations for NRLink

const ubyte NRLinkID = 0x02;

const ubyte NRLinkDataBytes = 0x40;

const ubyte NRLinkCommandReg = 0x41;

const ubyte NRLinkReadResult = 0x42;

const ubyte NRLinkWriteData = 0x42;

const tSensors NRLinkPort = NRLINK; // Connect NRLink sensor to this port!!

const ubyte NRLinkDefault = 0x44;

const ubyte NRLinkFlush = 0x46;

const ubyte NRLinkHighSpeed = 0x48;

const ubyte NRLinkLongRange = 0x4C;

const ubyte NRLinkShortRange = 0x53;

const ubyte NRLinkSetADPAON = 0x4E;

const ubyte NRLinkSETADPAOFF = 0x4F;

const ubyte NRLinkTxUnassembled = 0x55;

const ubyte NRLinkSelectPF = 0x50;

/////////////////////////////////////////////////////////////////////////////

// send Command to NrLink interface

/////////////////////////////////////////////////////////////////////////////

void NRLinkCommand(byte NRLinkCommand)

{

byte NRLinkMsg[5];

const byte MsgSize = 0;

const byte Address = 1;

const byte CommandAddress = 2;

const byte Command = 3;

// Build the I2C message

NRLinkMsg[MsgSize] = 3;

NRLinkMsg[Address] = NRLinkID;

NRLinkMsg[CommandAddress] = NRLinkCommandReg ;

NRLinkMsg[Command] = NRLinkCommand;

while (nI2CStatus[NRLinkPort] == STAT_COMM_PENDING)

{

// Wait for I2C bus to be ready

}

// when the I2C bus is ready, send the message you built

sendI2CMsg(NRLinkPort, NRLinkMsg[0], 0);

}

// Print the contents of the NRLink RAM starting and

// ending at the addresses given

// Each line is printed and the display wraps around

// every 8 lines

void readMacros(ubyte startAddr, ubyte endAddr) {

ubyte i, line;

ubyte addr;

const int kReplyLength = 1;

ubyte nReplyBytes[kReplyLength];

string s1, s2;

TI2CStatus err;

typedef struct{

byte nMsgSize;

byte nDeviceAddress;

byte nLocationPtr;

} TI2C_Output;

TI2C_Output sOutput;

sOutput.nMsgSize = 2;

sOutput.nDeviceAddress = 0x02;

sOutput.nLocationPtr = 0;

eraseDisplay();

line=0;

addr = startAddr;

for(i=(int)startAddr; i < (int)endAddr; i++) {

nI2CBytesReady[NRLinkPort]=0;

err = NO_ERR;

do {

err = nI2CStatus[NRLinkPort];

wait1Msec(2);

}while(err == STAT_COMM_PENDING);

sOutput.nLocationPtr = addr;

addr++;

sendI2CMsg(NRLinkPort, sOutput.nMsgSize, kReplyLength);

err = NO_ERR;

do {

err = nI2CStatus[NRLinkPort];

wait1Msec(2);

}while(err == STAT_COMM_PENDING);

err = nI2CStatus[NRLinkPort];

if (err == NO_ERR){

readI2CReply(NRLinkPort, nReplyBytes[0], kReplyLength);

StringFormat(s1, "%x: %d", i, nReplyBytes[0]);

//StringFormat(s2, "%2x %2x", nReplyBytes[1], nReplyBytes[2]);

s2 = "";

s2 += nReplyBytes[0];

nxtDisplayTextLine(line%8, "%s %s", s1, s2);

wait10Msec(100);

} else {

nxtDisplayTextLine(line%8, "%2x: err %d", i, err);

wait10Msec(100);

}

line++;

}

// Write the contents of the NRLink RAM into a file on the NXT that

// can be downloaded from the RobotC IDE onto your PC

// File is named testFile.dat

void dumpNRLinkRAM() {

int i;

byte addr;

const int kReplyLength = 1;

ubyte nReplyBytes[kReplyLength];

const string sFileName = "testFile.dat";

TFileIOResult nIoResult;

TFileHandle hFileHandle;

int nFileSize = 256;

TI2CStatus err;

typedef struct{

byte nMsgSize;

byte nDeviceAddress;

byte nLocationPtr;

} TI2C_Output;

TI2C_Output sOutput;

sOutput.nMsgSize = 2;

sOutput.nDeviceAddress = 0x02;

sOutput.nLocationPtr = 0;

Delete(sFileName, nIoResult);

hFileHandle = 0;

OpenWrite(hFileHandle, nIoResult, sFileName, nFileSize);

nxtDisplayTextLine(2, "Dumping NRLink");

addr = 0;

for(i=0x00; i <= 0xff; i++) {

nI2CBytesReady[NRLinkPort]=0;

err = NO_ERR;

do {

err = nI2CStatus[NRLinkPort];

wait1Msec(2);

}while(err == STAT_COMM_PENDING);

sOutput.nLocationPtr = addr;

addr++;

sendI2CMsg(NRLinkPort, sOutput.nMsgSize, kReplyLength);

err = NO_ERR;

do {

err = nI2CStatus[NRLinkPort];

wait1Msec(2);

}while(err == STAT_COMM_PENDING);

err = nI2CStatus[NRLinkPort];

if (err == NO_ERR){

readI2CReply(NRLinkPort, nReplyBytes[0], kReplyLength);

WriteByte(hFileHandle, nIoResult, nReplyBytes[0]);

} else {

WriteByte(hFileHandle, nIoResult, 0xff);

}

Close(hFileHandle, nIoResult);

nxtDisplayTextLine(3, "Done");

}

/////////////////////////////////////////////////////////////////////////////

// Run some commands and macro to control PF Motors using NRLink.

/////////////////////////////////////////////////////////////////////////////

task main()

{

nI2CBytesReady[NRLinkPort] = 0;

SensorType[NRLinkPort] = sensorI2CCustom9V; // Note, use this, NOT CustomFast9V!!

NRLinkCommand(NRLinkFlush);

NRLinkCommand(NRLinkDefault);

// NRLinkCommand(NRLinkLongRange);

NRLinkCommand(NRLinkSelectPF);

eraseDisplay();

dumpNRLinkRAM();

wait10Msec(100);

// print the contents of the NRlink RAM starting and ending at these addresses

readMacros(0x0, 0x17);

wait10Msec(1000);

}

Last updated 23 May, 2008

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