Next up was an HTU-21D Temperature/Relative Humidity sensor
Device id &40
- IMG_5017.jpeg (35.78 KiB) Viewed 130 times
This was the first device I tried where information was being read back and it proved to be a difficult learning curve (see post
viewtopic.php?t=5402) and hair puller (not that I have that much now) so a big thanks to those who contributed
The main problem, having worked out the i2c_io syntax, was that Minerva Mk2 doesn't implement clock stretching so i2c_io didn't wait for the measurement to be made before trying to read the result. So it was necessary to split the measurement request and read request into separate i2c_io commands and pause in-between them
The test code
Code: Select all
100 c$=CHR$(164) & CHR$(HEX('FE')) & CHR$(255): REMark Soft Reset
110 r$=I2C_IO(c$,0,HEX('40'),1)
120 PAUSE 20 : REMark pause after reset?
130 r$=GetValue("T"): PRINT "Temperature: " & r$ & "c"
140 r$=GetValue("H"): PRINT "Relative Humidity: " & r$ & "%"
150 DEFine FuNction GetValue(V$)
160 LOCal e,v,c$,r$
170 SELect ON V$
180 ="H","h": e=HEX("E5") : REMark Relative Humidity
190 ="T","t": e=HEX("E3") : REMark Temperature
200 END SELect
210 c$=CHR$(164) & CHR$(e) & CHR$(255)
220 r$=I2C_IO(c$,0,HEX('40'),1)
230 PAUSE 200 : REMark WHAT PAUSE NEEDED???
240 c$=CHR$(2) & CHR$(188) & CHR$(255)
250 r$=I2C_IO(c$,3,HEX('40'),1)
300 v=CODE(r$(2 TO 2))
310 v=v&&253 : REMark strip status bits
320 v=v+(CODE(r$)*256)
330 SELect ON V$
340 ="H","h": v=-6+125*(v/65336)
350 ="T","t": v=-46.85+175.72*(v/65536)
360 END SELect
370 v=INT(v*10)/10
400 RETurn v
500 END DEFine
And the output
Because of the timing issues the super basic extension will have options to:
a) Measure/Wait/Read
b) Just Measure
c) Just Read
d) soft reset
