Trying to make very simple code to read 74HC165
AGCB
Posts: 327
in Propeller 1
Trying and trying but no good yet.
Thanks
Aaron
CON
_clkmode = xtal1 + pll16x ' use crystal x 16
_xinfreq = 5_000_000 ' 5 MHz cyrstal (sys clockP = 80 MHz)
'Simple code to read in data from 74HC165 with DIP switch
clockP = 19 'clock pin (low to high edge triggered)
loadP = 18 'parallel load Pin (active low)
dataP = 16 'data pin Receives data from 165
obj
TV : "TV_text"
VAR
byte winput
long data_in
PUB main
tv.start(0)
waitcnt(clkfreq +cnt)
outa[loadP]~~ 'preset load pin high
dira[loadP]~~ ' make load pin output
dira[clockP]~~ ' make clock pin output
repeat
winput:=get_data
tv.bin(winput,8)
waitcnt(clkfreq*6+cnt) 'time to change switches
tv.cr
PUB get_data
data_in:=0
' pull clock low and single strobe to clear all
outa[CLOCKP] := 0
'##strobe low to latch inputs on 165
outa[loadP] := 0 'load pin low to load data from 8 inputs
wait
outa[loadP] := 1 ' Must go high here
wait
'##loop through all inputs and stick into data_in
'MSBPRE
repeat 8
'data_in := (data_in << 1) | ina[dataP]
data_in :=(data_in << 1) + ina[dataP]
wait
PostClock(clockP)
return data_in
PUB wait
waitcnt(clkfreq/100+cnt)
PUB PostClock(_clockP)
!outa[clockP]
wait
!outa[clockP]
Can you tell me what's wrong. I don't want to use complicated objects and can't find anything much for 74HC165. This will be for a wind direction sensor with 8 magnetsThanks
Aaron
Comments
pub rd_165(bits) outa[LD_165] := 0 ' blip Shift/Load line outa[LD_165] := 1 repeat bits result := (result << 1) | ina[DO_165] ' get bit outa[CLK_165] := 1 ' blip clock outa[CLK_165] := 0FWIW, I think the post set (~~) ad post clear (~) operators are confusing, and in tests I have found they're not as fast as simply setting things directly. I've attached my IO object as I use it to initialize the SPI pins to the '165.Another note: You don't need to slow down the process by putting the delay in the clock; in Spin you'll never outrun that chip. In my HC-8+ projects I use this unrolled code to read 17 digital inputs. It's more code, but faster without the loop overhead.
pri scan_ttl_ins : tempin ' call only from background() '' Scan TTL and DMX address inputs outa[LD_165] := 0 ' blip Shift/Load line outa[LD_165] := 1 tempin := ina[DMX_A8] ' bit16 ' unrolled for best speed tempin := (tempin << 1) | ina[DO_165] ' bit15 outa[CLK_165] := 1 ' blip clock outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] ' bit7 outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] outa[CLK_165] := 1 outa[CLK_165] := 0 tempin := (tempin << 1) | ina[DO_165] ' bit0 ttlpins := tempin.byte[0] ' update global vars dmxaddr := tempin >> 8So it may be a hardware problem. Have you connected the 'clock inhibit' pin (15) to ground?
Andy
and still got all 1s in the output.
As @ARIBA said " may be a hardware problem", I checked all connections and I found that for some reason I had a 10k pull up on the Q7 output pin. Removing that solved the problem!
Thank you all much!
Aaron
Edit: I should have read the last post more carefully. It looks like your code works fine. It looked fine when I read it as well.