74HC165 confusion!
eagletalontim
Posts: 1,399
Good evening all! I am tinkering with a 74HC165 and using the code posted below. When viewing the serial terminal, the output is either all 1's or all 0's.
I am attempting to read 7 switches that output 12V +. I have voltage divider circuits on each input pin that drops the voltage to 2.99V per input pin. The 165 is being powered from the 3.3V rail. The only time I am getting a reading is when I either ground or bring high the 8th input or input "H". According to the datasheet, "Unused inputs must always be tied to an appropriate logic voltage level (e.g., either GND or VCC)." I am using the 3 pin connection method to the Prop : Load, Clock, and Pin 9 on the 165 as the data.
What I am trying to accomplish is to get which pin is high, then run a "CASE" using the select case method according to what pin is high. If more info is needed, please feel free to ask.
_CLKMODE = XTAL1 + PLL16X
_XINFREQ = 5_000_000
CLOCK = 17 ' Connected to pin 2 of 74HC165
LOAD = 16 ' Connected to pin 1 of 74HC165
DATA = 18 ' Connected to pin 9 of 74HC165 (for inverted data use pin 7)
' The data pin should be connected to the Propeller with
' a 4.7K Ω series resistor.
BITS_IN = 8
DEBUG_BAUD = 9_600
DEBUG_HEADING_X = 2 ' Output formatting data
DEBUG_HEADING_Y = 2
DEBUG_DYNAMIC_X = DEBUG_HEADING_X + 8
DEBUG_DYNAMIC_Y = DEBUG_HEADING_Y + 2
VAR
long xInputs
OBJ
Pst : "Parallax Serial Terminal"
PUB Setup
Pst.Start(DEBUG_BAUD)
waitcnt(clkfreq * 3 + cnt) ' time to open serial terminal
dira[CLOCK] := 1
outa[LOAD] := 1
dira[LOAD] := 1
Pst.Clear
Pst.Position(DEBUG_HEADING_X, DEBUG_HEADING_Y)
Pst.Str(string("xInputs FEDCBA9876543210", 13))
Pst.PositionX(DEBUG_HEADING_X)
Pst.Str(string("------- ----------------", 13))
Pst.PositionX(DEBUG_HEADING_X)
Pst.Str(string("Status ................"))
MainLoop
PUB MainLoop
repeat
xInputs := 0 ' clear variable to hold input states
outa[LOAD] := 0
outa[LOAD] := 1
repeat BITS_IN
xInputs <<= 1
xInputs += ina[DATA]
outa[CLOCK] := 1
outa[CLOCK] := 0
Pst.Position(DEBUG_DYNAMIC_X, DEBUG_DYNAMIC_Y)
Pst.Bin(xInputs, BITS_IN)
I am attempting to read 7 switches that output 12V +. I have voltage divider circuits on each input pin that drops the voltage to 2.99V per input pin. The 165 is being powered from the 3.3V rail. The only time I am getting a reading is when I either ground or bring high the 8th input or input "H". According to the datasheet, "Unused inputs must always be tied to an appropriate logic voltage level (e.g., either GND or VCC)." I am using the 3 pin connection method to the Prop : Load, Clock, and Pin 9 on the 165 as the data.
What I am trying to accomplish is to get which pin is high, then run a "CASE" using the select case method according to what pin is high. If more info is needed, please feel free to ask.
Comments
pub x165_in(bits, shiftmode) | work '' Input value from 74x165(s) '' -- takes about 91us @ 80MHz outa[LD_165] := 0 ' load inputs outa[LD_165] := 1 work := 0 ' clear workspace bits := 1 #> bits <# 32 ' limit to legal value repeat bits ' read n bits work := (work << 1) | ina[DO_165] ' get new bit outa[CLK_165] := 1 ' blip clock outa[CLK_165] := 0 if (shiftmode == LSBFIRST) ' LSBFIRST result? work ><= bits ' reverse bits return work