NANO100: MCU Sine wave generator - using MCU DAC(Look up table with adjustable amplitude)

1.Generate sample point use octave.

	x = 0 : pi/64 : 2*pi;
	y = 0.5*(sin(x)+1);
	plot(y);

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2.Create look up table.use const to store look up table in ROM for less latency.

	#define SINE_LUT_SIZE (127)
	const float sine_lut[SINE_LUT_SIZE] =
	{
	0.500, 0.524, 0.549, 0.573, 0.597, 0.621, 0.645 ,0.664 ,0.694 ,0.718 ,0.730 ,0.755 ,0.779 ,0.795 ,0.810,
	0.835, 0.853, 0.870 ,0.881 ,0.900, 0.915, 0.928, 0.940, 0.951, 0.961, 0.970, 0.978, 0.985, 0.990, 0.994,
	0.997, 0.999, 1.000, 0.999, 0.997, 0.994, 0.990, 0.985, 0.978, 0.970, 0.961, 0.951, 0.940, 0.928, 0.915,
	0.901, 0.886, 0.870, 0.853, 0.835, 0.817, 0.797, 0.777, 0.757, 0.735, 0.713, 0.691, 0.668, 0.645, 0.621,
	0.597, 0.573, 0.549, 0.524, 0.500, 0.475, 0.450, 0.426, 0.402, 0.378, 0.354, 0.331, 0.308, 0.286, 0.264,
	0.242, 0.222, 0.202, 0.182, 0.164, 0.146, 0.129, 0.113, 0.098, 0.084, 0.071, 0.059, 0.048, 0.038, 0.029,
	0.021, 0.014, 0.009, 0.005, 0.002, 0.000, 0.000, 0.000, 0.002, 0.005, 0.009, 0.014, 0.021, 0.029, 0.038,
	0.048, 0.059, 0.071, 0.084, 0.098, 0.113, 0.129, 0.146, 0.164, 0.182, 0.202, 0.222, 0.242, 0.264, 0.286,
	0.308, 0.331, 0.354, 0.378, 0.402, 0.426, 0.450
	};

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3.Scale to real data function (for 12 bits DAC the max value is 4096)

	#define AMPLITUDE (4000.0)
	#define SINE_SCALE(x) (AMPLITUDE*(x))
	uint32_t index0 = 0;
	DAC_WRITE_DATA(DAC, 0, SINE_SCALE(sine_lut[index0]));

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nrf52 : Add CMSIS_DSP package in Keil 5

1.Open Manage Run-Time Environment and check the DSP

2.Include arm_math.h
  and  path in your project:Keil_v5\ARM\PACK\ARM\CMSIS\5.0.1\CMSIS\Include

3.Add symbol ARM_MATH_CM4 since nrf52832 use Cortex M4F

4.Simple matrix multiplication code

	const q31_t A[9] =
	{
	3, 3, 3,
	3, 3, 3,
	3, 3, 3
	};
	const q31_t X[9] =
	{
	1, 0, 0,
	0, 1, 0,
	0, 0, 1,
	};
	const q31_t Y[9] =
	{
	0, 0, 0,
	0, 0, 0,
	0, 0, 0,
	};
	int main(void)
	{
	arm_matrix_instance_q31 A_F;
	arm_matrix_instance_q31 X_F;
	arm_matrix_instance_q31 Y_F;
	arm_status status;
	uint32_t srcRows = 3,srcColumns = 3;
	arm_mat_init_q31(&A_F, srcRows, srcColumns, (q31_t *)A);
	arm_mat_init_q31(&X_F, srcRows, srcColumns, (q31_t *)X);
	arm_mat_init_q31(&Y_F, srcRows, srcColumns, (q31_t *)Y);
	status = arm_mat_mult_q31(&A_F, &X_F, &Y_F);
	while(status != ARM_MATH_SUCCESS);
	}

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Ref:
    1. CMSIS DSP Software Library