TS-7180 Quadrature: Difference between revisions

From embeddedTS Manuals
mNo edit summary
No edit summary
 
(One intermediate revision by the same user not shown)
Line 1: Line 1:
== Quadrature Counters ==
'''Quadrature Counters'''


The TS-7180 provides three independent quadrature counters.  The associated inputs are shown in the table below.
The TS-7180 provides three independent quadrature counters.  The associated inputs are shown in the table below.
Line 63: Line 63:




== Edge-Counters, Period-counters ==
'''Edge-Counters, Period-counters'''




For each input pin, there is an edge-counter, and a period-counter.  The former counts the positive edges on an input pin, while the latter may be used to measure the elapsed time between N positive-edges.
For each input pin, there is an edge-counter, and a period-counter.  The former counts the positive edges on an input pin, while the latter may be used to measure the elapsed time between N positive-edges.
Edge-counters are 16-bits wide, and their addresses are shown in the table below.
{| class="wikitable"
|-
|+ Edge Counters
! Input
! MSB
! LSB
! MSB Alias
|-
| DIG_IN_1
| 105
| 106
| 107
|-
| DIG_IN_2
| 108
| 109
| 110
|-
| DIG_IN_3
| 111
| 112
| 113
|-
| DIG_IN_4
| 114
| 115
| 116
|-
| DIO_6_IN
| 117
| 118
| 119
|-
| DIO_7_IN
| 120
| 121
| 122
|}
Period counters are 32-bits wide, and their addresses are shown in the table below.
{| class="wikitable"
|-
|+ Period Counters
! Input
! Byte 3
! Byte 2
! Byte 1
! Byte 0
|-
| DIG_IN_1
| 131
| 132
| 133
| 134
|-
| DIG_IN_2
| 135
| 136
| 137
| 138
|-
| DIG_IN_3
| 139
| 140
| 141
| 142
|-
| DIG_IN_4
| 143
| 144
| 145
| 146
|-
| DIO_6_IN
| 147
| 148
| 149
| 150
|-
| DIO_7_IN
| 151
| 152
| 153
| 154
|}
To use the period counters, it is first necessary to write N (for the number of edges to count) to address 155.  This may be done like so: 
<source lang=bash>
tshwctl -a 155 -w N
</source>
As soon as address 155 is written, counting begins, clocked at 63MHz.  After N edges have been detected, the period registers may be read.  The frequency of the input may be calculated from the period, as shown here:
<source lang=bash>
frequency = (N * 63000000) / period
</source>
Technologic Systems has provided a simple test program for accessing and displaying the values from the quadrature and edge-counters.  Download the source tarball here: [[File:Test-edges.tar.gz]]

Latest revision as of 12:19, 19 December 2018

Quadrature Counters

The TS-7180 provides three independent quadrature counters. The associated inputs are shown in the table below.

Quadrature
Quad # INPUTS
Quad0 DIG_IN_1 + DIG_IN_2
Quad1 DIG_IN_3 + DIG_IN_4
Quad2 DIO_6_IN + DIO_7_IN


Each of the quadrature counters (which are in the FPGA) is 16-bits wide, and are accessed via i2c. The addresses are shown below.


Quad # MSB LSB MSB Alias
Quad0 96 97 98
Quad1 99 100 101
Quad2 102 103 104


For example, to read the MSB for Quad1: 

tshwctl -r -a 99


The MSB aliases are used to detect 16-bit rollover. If the first reading of the MSB is not equal to the second, overflow/underflow was detected during the read.


Edge-Counters, Period-counters


For each input pin, there is an edge-counter, and a period-counter. The former counts the positive edges on an input pin, while the latter may be used to measure the elapsed time between N positive-edges.

Edge-counters are 16-bits wide, and their addresses are shown in the table below.

Edge Counters
Input MSB LSB MSB Alias
DIG_IN_1 105 106 107
DIG_IN_2 108 109 110
DIG_IN_3 111 112 113
DIG_IN_4 114 115 116
DIO_6_IN 117 118 119
DIO_7_IN 120 121 122


Period counters are 32-bits wide, and their addresses are shown in the table below.

Period Counters
Input Byte 3 Byte 2 Byte 1 Byte 0
DIG_IN_1 131 132 133 134
DIG_IN_2 135 136 137 138
DIG_IN_3 139 140 141 142
DIG_IN_4 143 144 145 146
DIO_6_IN 147 148 149 150
DIO_7_IN 151 152 153 154

To use the period counters, it is first necessary to write N (for the number of edges to count) to address 155. This may be done like so: 

tshwctl -a 155 -w N

As soon as address 155 is written, counting begins, clocked at 63MHz. After N edges have been detected, the period registers may be read. The frequency of the input may be calculated from the period, as shown here: 

frequency = (N * 63000000) / period


Technologic Systems has provided a simple test program for accessing and displaying the values from the quadrature and edge-counters. Download the source tarball here: File:Test-edges.tar.gz

Retrieved from "http://docs.embeddedTS.com/index.php?title=TS-7180_Quadrature&oldid=10194"