Trouble interfacing LPC2148 and Hitachi H48C accelerometer

[aforadi]

Hi People
The H48C has only one DIO pin. I cant figure out how to perform SPI comm. b/w LPC2148 and H48C since the LPC has MOSI and MISO.

I have tried connecting the MISO and DIO , CS of both and coded up.
But no help with that. I keep getting a mode fault with that. Any idea where I am going wrong?

 

[alexan_e]

You have to use simple I/O pins not the SPI.

The internal schematic of your accelerometer is this
View attachment 3 Axis Accelerometer_B Schematic.pdf

You can see that internally a MCP3204 ADC is used
**broken link removed**

You can figure the correct I/O timing from the diagrams of the ADC.

Alex

 

[aforadi]

This is what I understand
1. Select the accelerometer through CS.
2. Through a GPIO collect the output from the DIO

Then,
What signal do I give the clock? Is it decided my the sampling rate I desire(obviously less than equal to the acelerometers sampling rate)
Also, How do I extract the data which is coming in?

 

[alexan_e]

If you check page 15 of the MCP3204 datasheet there is a complete description for the serial communication of the ADC,
you have to study that to find the proper way to read it.
The clock will be pulsed manually from a pin H-L-H-L and for each change you will send/receive your data bit by bit.
I don't have a ready solution since i haven't used this before.

Alex

 

[aforadi]

OK..So now what I am doing is shorting the MOSI and MISO wires and connecting them to the DIO of the accelerometer.Here is the code I am using

#define SPIF (1<<7)
#define LED_MSK 0x00FF0000

void Initialize()
{
/* Configure Pin Connect Block */
PINSEL0=0x5500;
/* Set pclk to same as cclk */
VPBDIV=0x1;
/* Set to highest speed for SPI at 12 MHz- > 1.5 MHz */
S0SPCCR=0x8;
/* Device selected as master */
S0SPCR=0xC24; //12 bits at a time
IOSET0 |= 0x80;
}

int main (void) {
int a;
IODIR1 = LED_MSK; /* LED's defined as Outputs */

Initialize();
while (1)
{

IOSET0 |= 0x80;
IOCLR0 |= 0x80;

S0SPDR = 0x060;
while(!(S0SPSR & SPIF))
{
IOPIN1 = (IOPIN1 & ~LED_MSK) | (1 << 16) ;
}
a = S0SPDR;
while(!(S0SPSR & SPIF))
{
IOPIN1 = (IOPIN1 & ~LED_MSK) | (2 << 16) ;
}
IOSET0 |= 0x80;
} /* Loop forever */
}

Could someone please point out my error?

---------- Post added at 17:42 ---------- Previous post was at 17:40 ----------

With that code I am still getting a mode fault and the code gets stuck at the 2nd SPIF check and the 2nd LED stays bright due to that

 

[alexan_e]

You are still using the SPI, this will not work, you have to define 3 pins and use then as CLOCK,DATA and CS.
then you will manually change the pin states to send each bit and the clock pulses.

I have found the following code in another forum, i think it was intended for arduino, you can change it for ARM, you should be able to understand the code.

for example this is a part of the code below, i have added comments

  pinMode(DIO_pin, OUTPUT);  	// set DIO_pin as output
  digitalWrite(CS_pin, LOW);        // set CS_pin to 0
  digitalWrite(CLK_pin, LOW);       // set CLK_pin to 0
  delayMicroseconds(1);             // delay
  digitalWrite(DIO_pin, HIGH);      // set DIO_pin to 1
  digitalWrite(CLK_pin, HIGH);      // set CLK_pin to 1
  delayMicroseconds(1);             // delay

This is the complete code

//// VARS
int CS_pin = 9;
int DIO_pin = 10;
int CLK_pin = 11;

byte tempLSB = 0;
byte tempMSB = 0;

int aX = 0;
int aY = 0;
int aZ = 0;

//// FUNCTIONS
void StartMassurement() {
  pinMode(DIO_pin, OUTPUT);
  digitalWrite(CS_pin, LOW);
  digitalWrite(CLK_pin, LOW);
  delayMicroseconds(1);
  digitalWrite(DIO_pin, HIGH);
  digitalWrite(CLK_pin, HIGH);
  delayMicroseconds(1);

  }

void ShiftOutNibble(byte DataOutNibble) {
  for(int i = 3; i >= 0; i--) { // i = 3 ... 2 ... 1 ... 0
    digitalWrite(CLK_pin, LOW);
    // set DIO first
    if ((DataOutNibble & (1 << i)) == (1 << i)) {  // DataOutNibble AND 1 x 2^i Equals 1 x 2^i ?
	digitalWrite(DIO_pin, HIGH);

	}
    else {
	digitalWrite(DIO_pin, LOW);

	}
    // with CLK rising edge the chip reads the DIO from arduino in
    digitalWrite(CLK_pin, HIGH);
    // data rate is f_clk 2.0 Mhz --> 0,5 micro seeconds
    delayMicroseconds(1); // :-) just nothing
  }

}

void SampleIt() {
  digitalWrite(CLK_pin, LOW);
  delayMicroseconds(1);
  digitalWrite(CLK_pin, HIGH);
  delayMicroseconds(1);

  pinMode(DIO_pin, INPUT);
  digitalWrite(CLK_pin, LOW);
  delayMicroseconds(1);
  digitalWrite(CLK_pin, HIGH);
  if (digitalRead(DIO_pin)== LOW) {
    // Blink LED because ok
    }
}

byte ShiftInNibble() {
  byte resultNibble;
  resultNibble = 0;

    for(int i = 3 ; i >= 0; i--) {
	// The chip Shift out results on falling CLK
	digitalWrite(CLK_pin, LOW);
	delayMicroseconds(1); // :-) just nothing
	if( digitalRead(DIO_pin) == HIGH) {
	  resultNibble += 1 << i;
	}
	else {
	  resultNibble += 0 << i;
	}
	digitalWrite(CLK_pin, HIGH);
    }
return resultNibble;
}

void EndMessurement() {
  digitalWrite(CS_pin, HIGH);
  digitalWrite(CLK_pin, HIGH);
}

int GetValue(byte Axis) { // x = B1000, y = 1001, z = B1010
  int Result = 0;
  StartMassurement();
  ShiftOutNibble(Axis);
  SampleIt();
  Result =  (ShiftInNibble() << 8) + (ShiftInNibble() << 4) + ShiftInNibble();
  EndMessurement();

  return Result;
  }

//// SETUP
void setup() {
  Serial.begin(57600);
  pinMode(CS_pin, OUTPUT);
  pinMode(CLK_pin, OUTPUT);
  pinMode(DIO_pin, OUTPUT);
  // initialize device & reset
  digitalWrite(CS_pin,LOW);
  digitalWrite(CLK_pin,LOW);
  delayMicroseconds(1);
  digitalWrite(CS_pin, HIGH);
  digitalWrite(CLK_pin,HIGH);
}


//// LOOP
void loop() {
  Serial.print(2048 - GetValue(B1000));
  Serial.print(" ");
  Serial.print(2048 - GetValue(B1001));
  Serial.print(" ");
  Serial.print(2048 - GetValue(B1010));


  Serial.println("");
}

This is where i found the code
**broken link removed**

Alex