How to get right digree? Nrf52811 direction finding

[miaojb12]

This is the config fun followed。

one sample every 125ns,one ant get 12us =96 samples.

and first 2+32 samples is ignored。

********************************************************************

// 1st ant 96 data of phase
0: -67 -55 -43 -31 -19 -7 6 18
8: 29 42 53 66 77 89 102 113
16: 125 137 149 161 173 186 198 -190
24: -179 -167 -156 -145 -134 -122 -111 -98
32: -86 -74 -61 -49 -36 -24 -12 2
40: 15 27 39 51 62 73 83 93
48: 103 114 124 134 145 157 169 180
56: 191 -198 -186 -174 -162 -149 -137 -124
64: -111 -99 -86 -74 -62 -50 -39 -28
72: -17 -5 8 20 31 42 54 66
80: 78 89 101 113 123 131 137 141
88: 143 141 78 -33 -35 -34 -28 -21

// 2nd ant 96 data of phase

96: -10 7 24 39 49 57 63 72
104: 82 95 110 124 137 150 162 173
112: 185 196 -194 -183 -171 -159 -148 -137
120: -127 -116 -104 -93 -81 -68 -57 -45
128: -34 -22 -10 4 15 27 39 51
136: 64 76 88 100 112 123 136 148
144: 160 172 184 195 -194 -183 -172 -160
152: -149 -137 -125 -111 -99 -87 -76 -65
160: -54 -43 -32 -20 -8 5 17 28
168: 40 52 65 77 89 100 112 124
176: 137 149 161 174 186 198 -192 -181
184: -171 -161 -150 -141 -131 -122 -113 -103

// 3rd ant 96 data of phase

192: -94 -84 -73 -61 -47 -35 -21 -8
200: 7 21 35 48 62 74 86 99
208: 111 122 134 147 158 171 181 193
216: -197 -187 -176 -165 -153 -140 -128 -117
224: -106 -94 -82 -71 -58 -46 -34 -23
232: -12 2 14 26 39 51 63 75
240: 88 100 112 124 136 148 159 172
248: 183 196 -193 -181 -169 -158 -147 -135
256: -124 -113 -101 -89 -77 -65 -54 -43
264: -32 -21 -11 2 14 25 38 51
272: 63 76 88 99 109 117 120 117
280: 109 97 84 75 71 71 76 86

// 4th ant 96 data of phase

288: 99 114 128 140 150 159 169 180
296: 192 -196 -183 -171 -159 -148 -136 -124
304: -112 -100 -87 -75 -62 -49 -36 -24
312: -13 -2 10 20 31 42 54 65
320: 78 90 102 114 125 137 148 161
328: 173 184 197 -193 -182 -170 -159 -147
336: -136 -125 -114 -102 -90 -78 -66 -54
344: -41 -28 -16 -4 10 21 34 46
352: 58 70 81 93 104 115 126 138
360: 150 162 174 186 198 -191 -181 -169
368: -158 -146 -133 -121 -108 -94 -78 -58
376: -35 -14 6 19 31 41 52 63

// 5th ant 96 data of phase

384: 76 89 103 116 126 136 146 155
392: 165 175 184 194 -196 -186 -175 -164
400: -153 -142 -130 -119 -108 -96 -85 -73
408: -61 -48 -35 -22 -9 4 16 28
416: 40 52 64 75 87 99 111 122
424: 134 146 158 170 181 193 -197 -185
432: -174 -163 -152 -140 -128 -117 -105 -92
440: -80 -68 -56 -44 -31 -19 -8 6
448: 18 30 42 54 67 78 90 103
456: 115 126 138 150 163 175 186 198
464: -190 -179 -166 -154 -141 -129 -117 -106
472: -94 -82 -71 -59 -48 -36 -25 -13

********************************************************************
void or_cfg()
{
NRF_RADIO->DFEMODE = RADIO_DFEMODE_DFEOPMODE_AoA;
NRF_RADIO->DFECTRL1 = 1<<RADIO_DFECTRL1_SAMPLETYPE_Pos| // 1:MagPhase 0:IQ
//--time 10*8 us
10 << RADIO_DFECTRL1_NUMBEROF8US_Pos |
//--crc behind
1 << RADIO_DFECTRL1_DFEINEXTENSION_Pos |
//--1:4us 2:2us 3:1us --> one sample len
2 << RADIO_DFECTRL1_TSWITCHSPACING_Pos |
1 << RADIO_DFECTRL1_TSAMPLESPACINGREF_Pos |
6 << RADIO_DFECTRL1_TSAMPLESPACING_Pos ;

//NRF_RADIO->DFECTRL2 = ((-32<<16)&0xfff0000)| //sample
// 0<<0; //switch

NRF_RADIO->CTEINLINECONF = 1 << RADIO_CTEINLINECONF_CTEERRORHANDLING_Pos |
0 << RADIO_CTEINLINECONF_CTEINFOINS1_Pos;

//DFE pin config
NRF_RADIO->PSEL.DFEGPIO[0] = ANTE;
NRF_RADIO->PSEL.DFEGPIO[1] = ANTS;
NRF_RADIO->PSEL.DFEGPIO[2] = ANTW;
NRF_RADIO->PSEL.DFEGPIO[3] = ANTN;

NRF_RADIO->SWITCHPATTERN = 1;//--for data recv
NRF_RADIO->SWITCHPATTERN = 1;//--for ref
NRF_RADIO->SWITCHPATTERN = 1;//--4us temp about 32 samples

NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;//5
NRF_RADIO->SWITCHPATTERN = 1;

NRF_RADIO->SWITCHPATTERN = 2;
NRF_RADIO->SWITCHPATTERN = 2;
NRF_RADIO->SWITCHPATTERN = 2;
NRF_RADIO->SWITCHPATTERN = 2;
NRF_RADIO->SWITCHPATTERN = 2;//5
NRF_RADIO->SWITCHPATTERN = 2;/**/

NRF_RADIO->SWITCHPATTERN = 4;
NRF_RADIO->SWITCHPATTERN = 4;
NRF_RADIO->SWITCHPATTERN = 4;
NRF_RADIO->SWITCHPATTERN = 4;
NRF_RADIO->SWITCHPATTERN = 4;//5
NRF_RADIO->SWITCHPATTERN = 4;

NRF_RADIO->SWITCHPATTERN = 8;
NRF_RADIO->SWITCHPATTERN = 8;
NRF_RADIO->SWITCHPATTERN = 8;
NRF_RADIO->SWITCHPATTERN = 8;
NRF_RADIO->SWITCHPATTERN = 8;//5
NRF_RADIO->SWITCHPATTERN = 8;
//-------------------------------------
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;//5
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;
NRF_RADIO->SWITCHPATTERN = 1;

NRF_RADIO->DFEPACKET.PTR = (u32)df_buf;
NRF_RADIO->DFEPACKET.MAXCNT = O_sizeof(df_buf);
}

[miaojb12]

sorry,changed < first 2+16 samples is ignored。>

[Dmitry]

Hi,

could you visualize your data as a plot or at least put CSV here? It's really hard to parse tons of digits in the head 

From your config - all 96 samples falls under the first antenna - we won't see any phase change.

IMHO switch pattern is too complex and outstretched, you should use as short switching slot as your antenna switching IC allows, ideally not longer than 2 usec (longer slot -> more crystal jitter influence -> lower accuracy). That's why reference period is separated - you have enough time on a single antenna to calculate frequency offset, and you have no chance to do that with two samples (4us sample spacing) - at least 8 samples are needed.

[miaojb12]

thanks for your reply.

our antenna switching ic is "SKY13322-375LF",whitch's switching time is 60ns.
We got 96 data for each ant.

1-16 ignored(may be changed with the switch)
17-80 used for compute average phase
81-96 ignored(may be changed with the switch)

//-----------------------------------------------------------------------------------------------

How we compute phase
1:we have 4 ants all;
2:we get 1st ant and 5th ant the same one
3:comput frequency offset beteen receiver and transmitter with 1sth and 5th ant(whitch is same ant)
(longer slot -> more crystal jitter influence -> lower accuracy) may resoved?
frequency offset <0.2%wave change,like 11.373,11.372,11.374,11.370
If frequency offset is 0, we will get num like, 12.500 beteen each data.
4:use 17-80 datas of each ant compute average phase
5:compute phase back to the time of first ant.
//--------------------
example
1th average phase:221
5th average phase:166
will get the change beteen each data is 11.373(frequency offset=22.54kHz )

2nd average phase:296 --> 9(phase of 2nd at 1st ant time)
(296-(11.373*96))=-795
-795+402*2 = 9

3rd average phase:249 -->76(phase of 3rd at 1st ant time)
4th average phase:271 -->-190(phase of 4th at 1st ant time)

//-------------------------------------------------------------

Is there any mistake?

[Dmitry]

miaojb12 said:

our antenna switching ic is "SKY13322-375LF",whitch's switching time is 60ns.

good.

miaojb12 said:

1-16 ignored(may be changed with the switch)
17-80 used for compute average phase
81-96 ignored(may be changed with the switch)

it's better to look at the plot, hard to say exactly where slots are changed. In theory you have two samples for reference period then continuous set of 0.125us samples after 1us gap.

miaojb12 said:

3:comput frequency offset beteen receiver and transmitter with 1sth and 5th ant(whitch is same ant)

as a variant, but

miaojb12 said:

(longer slot -> more crystal jitter influence -> lower accuracy) may resoved?

what I mean - the distance between points that you compare should be as short as possible, a jitter is really noticeable. You have 12us slots, it's too long. Of course you can average between multiple periods, but I see no reason for adding jitter error if you can work with shorter slots.

miaojb12 said:

4:use 17-80 datas of each ant compute average phase

Maybe I didn't understand clearly, but you should apply frequency offset correction to each sample before calculating average phase.

[miaojb12]

I draw a pic, wish you can understand what i mean.