How stable would this be as a no hardware distance sensor?
Jorge P
Posts: 385
I was writing and testing some code for a project I have in Customer Projects, when I noticed that each time I placed my hand within 1.5 to 2 inches it would be detected by a hanging wire connected to a propeller pin. I have I2C code running on the pin next to it so I am curious if it is creating capacitance...
Here is the code I was working on
I have never noticed this with the Propeller before.
Can an anomaly like this be relied upon to work all the time?
Here is a video showing it:
Here is the code I was working on
{{
HC-SR04 Trigger Driver
8x HC-SR04 are used
All Trig pins are connected to the MCP23017 on seperate lines
All echo pins are tied together and connected to the Propeller
Only one HC-SR04 is read at a time clockwise from Left of the
robot device
License: MIT
Copyright (c) 2011-2018 Jorge Joaquin Pareja
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject
to the following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE
}}
CON
_clkmode = xtal1 + pll16x 'Standard clock mode * crystal frequency = 80 MHz
_xinfreq = 5_000_000
' Connect up to 16 trigger pins to the MCP23017
' Connect all echo pins together and connect them to a free Propeller pin and define that pin as ECHO below
SDA = 0 ' Prop pin 0
SCL = 1 ' Prop pin 1
ECHO = 2
'Hardware addressable pins 15, 16, and 17
'|||
MCPADDR = %0100_000 ' leave off the R/W bit, Address is shifted right to put the bit in by the driver
INPUT_BIT = %1
OUTPUT_BIT = %0
ALLOUTPUT = %0000_0000
ALLINPUT = %1111_1111
ALLOFF = %0000_0000
TRIG_0 = %0000_0001 ' Left Center GPA0
TRIG_1 = %0000_0010 ' Left Front GPA1
TRIG_2 = %0000_0100 ' Front Center GPA2
TRIG_3 = %0000_1000 ' Right Front GPA3
TRIG_4 = %0001_0000 ' Right Center GPA4
TRIG_5 = %0010_0000 ' Right Rear GPA5
TRIG_6 = %0100_0000 ' Rear Center GPA6
TRIG_7 = %1000_0000 ' Left Rear GPA7
TRIG_8 = %0000_0001 ' spare
TRIG_9 = %0000_0010 ' spare
TRIG_10 = %0000_0100 ' spare
TRIG_11 = %0000_1000 ' spare
TRIG_12 = %0001_0000 ' spare
TRIG_13 = %0010_0000 ' spare
TRIG_14 = %0100_0000 ' spare
TRIG_15 = %1000_0000 ' spare
' MCP CONFIG Registers ICON.BANK = 0
IODIRA = $00
IODIRB = $01
IPOLA = $02
IPOLB = $03
GPINTENA = $04
GPINTENB = $05
DEFVALA = $06
DEFVALB = $07
INTCONA = $08
INTCONB = $09
IOCON = $0A
GPPUA = $0C
GPPUB = $0D
INTFA = $0E
INTFB = $0F
INTCAPA = $10
INTCAPB = $11
GPIOA = $12
GPIOB = $13
OLATA = $14
OLATB = $15
' from Timing.spin
_10us = 1_000_000 / 10 ' Divisor for 10 us
_1ms = 1_000_000 / 1_000 ' Divisor for 1 ms
_1s = 1_000_000 / 1_000_000 ' Divisor for 1 s
DEBUG = 1
VAR
LONG clkcycles '
OBJ
mcp : "i2cDriver.spin"
pst : "Parallax Serial Terminal.spin" ' only use for debugging or it slows us down
PUB MAIN | tmp, pass
' init pst
pst.Start(115200)
mcp.Init(SCL, SDA)
MCP_Config
pass := 1
tmp := 0
REPEAT
USS_Read(tmp)
tmp++
IF tmp == 16
tmp := 0
pst.Clear
pst.Str(STRING("Pass: "))
pst.Dec(pass)
pst.NewLine
pass++
PUB MCP_Config
' set all pins to output
MCP_Write(IODIRA, ALLOUTPUT)
MCP_Write(IODIRB, ALLOUTPUT)
MCP_Write(GPIOA, %0000_0000)
MCP_Write(GPIOB, %0000_0000)
PUB USS_Read(device) | cnt1, cnt2, Microseconds, Distance
CASE device
0:
MCP_PinGPB(ALLOFF)
MCP_PinGPA(TRIG_0)
WaitUsec10
MCP_PinGPA(ALLOFF)
1:
MCP_PinGPB(ALLOFF)
MCP_PinGPA(TRIG_1)
WaitUsec10
MCP_PinGPA(ALLOFF)
2:
MCP_PinGPB(ALLOFF)
MCP_PinGPA(TRIG_2)
WaitUsec10
MCP_PinGPA(ALLOFF)
3:
MCP_PinGPB(ALLOFF)
MCP_PinGPA(TRIG_3)
WaitUsec10
MCP_PinGPA(ALLOFF)
4:
MCP_PinGPB(ALLOFF)
MCP_PinGPA(TRIG_4)
WaitUsec10
MCP_PinGPA(ALLOFF)
5:
MCP_PinGPB(ALLOFF)
MCP_PinGPA(TRIG_5)
WaitUsec10
MCP_PinGPA(ALLOFF)
6:
MCP_PinGPB(ALLOFF)
MCP_PinGPA(TRIG_6)
WaitUsec10
MCP_PinGPA(ALLOFF)
7:
MCP_PinGPB(ALLOFF)
MCP_PinGPA(TRIG_7)
WaitUsec10
MCP_PinGPA(ALLOFF)
8:
MCP_PinGPA(ALLOFF)
MCP_PinGPB(TRIG_8)
WaitUsec10
MCP_PinGPB(ALLOFF)
9:
MCP_PinGPA(ALLOFF)
MCP_PinGPB(TRIG_9)
WaitUsec10
MCP_PinGPB(ALLOFF)
10:
MCP_PinGPA(ALLOFF)
MCP_PinGPB(TRIG_10)
WaitUsec10
MCP_PinGPB(ALLOFF)
11:
MCP_PinGPA(ALLOFF)
MCP_PinGPB(TRIG_11)
WaitUsec10
MCP_PinGPB(ALLOFF)
12:
MCP_PinGPA(ALLOFF)
MCP_PinGPB(TRIG_12)
WaitUsec10
MCP_PinGPB(ALLOFF)
13:
MCP_PinGPA(ALLOFF)
MCP_PinGPB(TRIG_13)
WaitUsec10
MCP_PinGPB(ALLOFF)
14:
MCP_PinGPA(ALLOFF)
MCP_PinGPB(TRIG_14)
WaitUsec10
MCP_PinGPB(ALLOFF)
15:
MCP_PinGPA(ALLOFF)
MCP_PinGPB(TRIG_15)
WaitUsec10
MCP_PinGPB(ALLOFF)
' Start reading
WAITPNE(0, |< ECHO, 0)
cnt1 := CNT
WAITPEQ(0, |< ECHO, 0)
cnt2 := CNT
Microseconds := (||(cnt1 - cnt2) / (CLKFREQ / 1_000_000)) >> 1
if DEBUG == 1
pst.Home
pst.ClearEnd
pst.Dec(Microseconds)
pst.Str(STRING(" us. "))
Distance := Millimeters(Microseconds)
IF DEBUG == 1
pst.Dec(Distance)
pst.Str(STRING(" mm."))
pause1ms(100)
'From Timing.spin
PUB pause1ms(period)
'' Pause execution for period (in units of 1 ms).
clkcycles := ((CLKFREQ / _1ms * period) - 4296) #> 381 ' Calculate 1 ms time unit
WAITCNT(clkcycles + CNT) ' Wait for designated time
PUB Millimeters(ms) : Distance
''Measure object distance in millimeters
Distance := ms * 10_000 / TO_CM ' Distance In Millimeters
PUB WaitUsec10
WAITCNT ((mcp#uSec * 10) + cnt)
PUB MCP_PinGPA(data)
mcp.WriteByteA8(MCPADDR, GPIOA, data)
PUB MCP_PinGPB(data)
mcp.WriteByteA8(MCPADDR, GPIOB, data)
PUB MCP_Write(reg, data)
mcp.WriteByteA8(MCPADDR, reg, data)
DAT
TO_CM LONG 29_386
I have never noticed this with the Propeller before.
Can an anomaly like this be relied upon to work all the time?
Here is a video showing it:
Comments
Mike R...
I've attached my MCP23017 object in case you'd like to compare code.
The I2C driver is based off your code, modified by Erlend Fj. Your included zip seems newer so I'll give it a try.
No, our circuits are a big wobbly jelly of electric and magnetic fields that allow every part to interact with every other, including parts that we don't think of as being in the circuit, like your hand. In ways that are often difficult to fathom. Ping on one part of that jelly and all the other parts quiver.