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\ Read DHT22 (bitbang) \ TI MSP430G2553 Launchpad with noForth mv 2553 240101

(* To do: timeout

History V0065 - Temperature in tenths of a degree. mk 20250424 V0064 - Loops named with ( A ) … ( D ). Variants of loops B and D studied. This loop variation of B and D work well. Comments revised. mk 20250423 05:25 V0063 - Cleaned up the code. Data output reduced to the essentials. mk 20250421 02:04 V0062 - Works well, output rounded to whole digits. mk 20250419 21:51 Previous versions: Successive approximation to the solution.

Patch millisecond to 100 microseconds. See: config2553.f

00c7 10B2 rom!  
hex 10B2 DMP

After COLD this value is active.

addr acronym registername 020 P1IN Input 021 P1OUT Output 022 P1DIR Direction 023 P1IFG Interupt Flag 024 P1IES Interrupt Edge Select 025 P1IE Interrupt Enable 026 P1SEL Port Select 041 P1SEL2 Port Select2 027 P1REN Resistor Enable *)

asm\
hex

\ helper code cls ( – ) s0 # sp mov next end-code \ clear stack

code p1H #1 021 & .b bis next end-code \ set lines code p1L #1 021 & .b bic next end-code code p6H 40 # 021 & .b bis next end-code code p6L 40 # 021 & .b bic next end-code

\ Assign DHT22 data line to pin p1.0, controll pin to p1.6 : Pio ( – ) \ set I/O function

41 027 *bic \ p1ren off
41 025 *bic \ p1ie  disable interrupt
41 026 *bic \ P1SEL I/0
41 041 *bic \ P1SEL2 I/0 
41 022 *bis \ set out for P1.0, P1.6
;

: wakeup ( – ) \ notify sensor to prepare the data

pio p1H p6H 1 ms  p1L 10 ms  ( p6L ) p1H  ; \ 1 ms == 100┬Ás !

Code @data ( – sun moon hum tmp chk chksum ) \ read sensor data \ get response time

#1 022 & .b bic \ p1,0 IN
#0 sun      mov   
#1 024 & .b bis \ FALLING EDGE\__
#1 023 & .b bic  \ clear P1IFG

40 # 021 & .b bic \ p6L_ (for logic analyser) begin, ( A ) \ wait for edge #1 023 & .b bit \ test bit \ Z: Set if result is zero, reset otherwise \ C: Set if result is not zero, reset otherwise (.NOT. Zero) cc? while, #1 sun add repeat,
40 # 021 & .b bis \ _/p6H (for logic analyser)

tos sp -) mov   
sun tos   mov   ( -- sun )

\ get startpulse time

#0 moon     mov   
#1 024 & .b bic \ ___/ RISING EDGE
#1 023 & .b bic  \ clear P1IFG

40 # 021 & .b bic \ p6L_ (for logic analyser) begin, ( B ) \ wait for edge #1 023 & .b bit \ test bit \ Z: Set if result is zero, reset otherwise \ C: Set if result is not zero, reset otherwise (.NOT. Zero) cc? while, #1 moon add repeat,
40 # 021 & .b bis \ _/p6H (for logic analyser)

tos sp -)  mov   
moon tos   mov   ( -- moon )

\ read 40 bits to array

#0 xx mov  \ init array
#0 yy mov
#0 zz mov 
dm 40 # day mov
begin, ( C )
  #1 023 & .b bic \ clear P1IFG 
  begin,           \ wait for edge
    #1 023 & .b bit \ test IFG
    \ Z: Set if result is zero, reset otherwise
    \ C: Set if result is not zero, reset otherwise (.NOT. Zero)
  cs? until,
  \ wait to read bit
  moon w mov 
w w add     \  2*moon, Loop D is about twice as fast as loop B.

40 # 021 & .b bic \ p6L_ (for logic analyser) begin, ( D ) #1 w sub
0=? until, \ read bit 40 # 021 & .b bis \ /p6H (for logic analyser)

  020 & w .b mov  \ read data line: bit H or L
  #1 w       bia   \ get bit
    \ tos sp -) mov  
    \ w tos     mov  ( ... -- ... bit ) \ test
    \ #1 sr bic  \ clear carry bit
\ shift left all bits
  zz zz add   
  yy yy addc
  xx xx addc
  w  zz bix   \ = xor : write data bit
#1 day sub
0=? until, \ 40 bits are read
\ adjust bits
8 # day mov  \ lshift 40 bits up 8x -> xx=hum yy=tmp 
begin,
  zz zz add 
  yy yy addc
  xx xx addc
  #1 day sub
0=? until,
\ push data to stack
tos sp -)  mov   xx tos mov  ( -- xx ) 
tos sp -)  mov   yy tos mov  ( -- yy ) 
zz swpb  \ get upper byte
tos sp -)  mov   zz tos mov  ( -- zz.b ) 
\ calculate checksumme
#0 w mov
xx w .b add   xx swpb   xx w .b add
yy w .b add   yy swpb   yy w .b add
tos sp -)  mov  
w tos   mov

next end-code

\ display decimal : (dht22) ( – sun moon hum tmp chk chksum )

cls wakeup @data 
;

: decemit ( c – ) \ print c from DEC special character set

hx 1B emit  [char] ( emit  [char] 0 emit   emit 
hx 1B emit  [char] ( emit  [char] B emit   \ back to normal output
;

: .tmp ( tmp – )
10 /mod 3 .r [char] , emit .

[char] f decemit 
[char] C emit space
;  \ ja, geht.

: .hum ( hum – ) \ rounded to whole percent

10 / . ." %rel" space 
;

: dht22 ( – ) \ print temperatur and humidity

cr (dht22)   ( 2 + ) \ add 2 for 'else' part
= if ." chk  " else ." chksum error" cls exit then
.tmp space space  .hum space space
\ ( sun moon -- ) drop drop 
  ( sun moon -- )  . .      \ testing
;

( The DHT22 starts its next measurement AFTER the query and saves the values. These are output with the next query, so they are old. For up-to-date values, query twice. There must be more than 2 seconds between each query, otherwise the DHT22 will not respond again. )

: test ( n – )

>r
cr ." discard old values..." (dht22) cls 
cr ." reading current data:"
r> 0 do   
  dm 40000 ms  \ wait until the sensor is ready again.
  dht22  
loop
;

shield nn\ freeze ( finis)

**This is an old revision of the document!**

This is an old revision of the document!