The Atan2LookupFP function finds the arctangent of y/x. It returns
the angle made by the vector 
with respect to origin. The
angle returned by atan2 will also contain the quadrant information.
Atan2LookupFP is a fixed point version of the standard atan2
function. This function implements the atan2 using a lookup table
approach. The values in the look up table are represented in Q4.12
format and so the values returned by this function are in Q4.12. A
maximum error of 0.2 degrees is present in the range of 89 to 90 degrees
when compared to the standard atan2 function available in glibc. For the
other angles (0 to 89) the maximum error is in the order of 10-3. This
function returns 0 when both xs and ys are zeroes.
API Syntax
short Atan2LookupFP(short xs, short ys, int M1,int N1,int M2, int N2)
Parameter Descriptions
The following table describes the template and the function parameters.
| Parameter | Description |
|---|---|
| xs | 16-bit signed value x in fixed point format of QM1.N1 |
| ys | 16-bit signed value y in fixed point format of QM2.N2 |
| M1 | Number of bits to represent integer part of x. |
| N1 | Number of bits to represent fractional part of y. Must be equal to 16-M1. |
| M2 | Number of bits to represent integer part of y. |
| N2 | Number of bits to represent fractional part of y. Must be equal to 16-N1. |
| Return | Return value is in radians. Its range varies from -pi to +pi in fixed point format of Q4.12 |
..rubric:: Resource Utilization
The following table summarizes the resource utilization of the
Atan2LookupFP function , generated using Vivado HLS 2019.1 tool for
the Xilinx Xczu9eg-ffvb1156-1-i-es1 FPGA.
Operating Frequency (MHz) |
Utilization Estimate | ||||
|---|---|---|---|---|---|
| BRAM_18K | DSP_48Es | FF | LUT | CLB | |
| 300 | 4 | 2 | 275 | 75 | 139 |
Performance Estimate
The following table summarizes the performance in different configurations, as generated using Vivado HLS 2019.1 tool for the Xilinx Xczu9eg-ffvb1156-1-i-es1 FPGA.
Operating Frequency (MHz) |
Latency Estimate | |
|---|---|---|
| Min (cycles) | Max (cycles) | |
| 300 | 1 | 15 |