P2 with Ping - Ping echo'd pulse not seen @ P2 pin, though appears @ Ping signal out
dgately
Posts: 1,639
Howdy,
Using John Abshier's PingDemo.spin2 code (https://github.com/parallaxinc/propeller/tree/master/examples/EZLib), I'm not able to receive the echo pulse from a Parallax Ping, though a logic probe does see the echo pulse returned. I'm using the schematic from the P1 C demo tutorial @ learn.parallax.com/tutorials/language/propeller-c/propeller-c-simple-devices/sense-distance-ping. I assumed that the schematic should work for P2 as well...
Set up this way, the logic analyzer displays:
If I connect the logic probe directly to the Ping signal pin:
The analyzer displays the proper echo pulse:
So, John Absheir's code appears to work (the echo pulse is emitted from the Ping), but I'm not sure why the signal does not appear at the P2 pin. I've tried several resistor values (3.3k, 1.2k, etc) with no change. Since I'm physically not seeing the echo pulse after the resistor, is there something on the P2 pin side that needs to be present (pull-up or pull-down resistors don't make sense, correct?).
Any help appreciated,
dgately
Using John Abshier's PingDemo.spin2 code (https://github.com/parallaxinc/propeller/tree/master/examples/EZLib), I'm not able to receive the echo pulse from a Parallax Ping, though a logic probe does see the echo pulse returned. I'm using the schematic from the P1 C demo tutorial @ learn.parallax.com/tutorials/language/propeller-c/propeller-c-simple-devices/sense-distance-ping. I assumed that the schematic should work for P2 as well...
Set up this way, the logic analyzer displays:
If I connect the logic probe directly to the Ping signal pin:
The analyzer displays the proper echo pulse:
So, John Absheir's code appears to work (the echo pulse is emitted from the Ping), but I'm not sure why the signal does not appear at the P2 pin. I've tried several resistor values (3.3k, 1.2k, etc) with no change. Since I'm physically not seeing the echo pulse after the resistor, is there something on the P2 pin side that needs to be present (pull-up or pull-down resistors don't make sense, correct?).
Any help appreciated,
dgately
Comments
-Phil
John Abshier
The main code calls a Ping Inches function: Then, the call chain goes like this. I have 3 questions embedded as UPPERCASE comments within:
PUB Inches(Pin) : Distance | to_in ''Measure object distance in inches TO_IN := 73_746 ' Inches make a con when make Ping Object Distance := Ticks(Pin) * 1_000 / TO_IN ' Calls Ticks and calculates Distance In Inches PUB Ticks(Pin) : microSeconds | timeOut timeOut := clkfreq / 1_000 * 20 ' max Ping time is 18.5 milliseconds pins.PulseoutUs(Pin,HIGH,5) ' Calls PulseoutUS to initiate the 5 usec pulse microSeconds := pins.PulseinUs(Pin, HIGH, timeOut) microSeconds >>= 1 ' divide by 2 to only get return time not out and back ser.dec(microSeconds) PUB PulseoutUs(_pin, _polarity, _time) | microSec '' Sends one pulse on a pin time in microseconds '' Input Parameters: _pin a pin number 0-63. Pins 58-36 for advanced users '' _polarity 0 for low pulse, 1 for high pulse. If not valid method just returns '' _time length of pulse in microseconds microSec := clkfreq / 1_000_000 if _polarity == HIGH_PULSE asm drvl _pin ' establish starting pin condition endasm _time := _time * microSec - 2 asm drvh _pin waitx _time '' DOESN'T THIS 'drvl _pin' TRI-STATE THE PIN AT THE END OF THIS FUNCTION ??? drvl _pin endasm elseif _polarity == LOW_PULSE asm drvh _pin ' establish starting pin condition endasm microSec := clkfreq /1_000_000 _time := _time * microSec - 2 asm drvl _pin waitx _time drvh _pin endasm '' SHOULD THIS CODE TRI_STATE THE PIN ON EACH INVOCATION ??? PUB PulseinUs(_pin, _polarity,_timeout) : pulse | microSec '' Measures a single pulse and rurn the length of the pulse in microseconds or an error flag '' Input parameters: See PulseinClk '' Output: Pulse length in microseconds or error flag as described in PulseinClk ' *** not tested after modifying to properly return error flag pulse := PulseinClk(_pin, _polarity,_timeout) / microSec if pulse > 0 microSec := clkfreq / 1_000_000 pulse /= microSec '' SHOULD THIS CODE TRI_STATE THE PIN ON EACH INVOCATION ??? PUB PulseinClk(_pin,_polarity,_timeout) : pulse | timeOut, startTime, startEdge, endEdge '' Measures a single pulse and return the length of the pulse in clock ticks or an error flag '' Input parameters: _pin A pin number 0-63. Pins 58-63 for advanced users '' _polarity 1 for a high pulse, 0 for a low pulse '' _timeout Time in clock ticks to wait for an edge '' Output: Pulse length in clock ticks '' Error outputs -1 for _polarity not in (0,1) -2 timed out on start edge -3 timed out on end edge if _polarity == HIGH_PULSE startEdge := %001 << 6 | _pin 'low to high endEdge := %010 << 6 | _pin 'high to low elseif _polarity == LOW_PULSE startEdge := %010 << 6 | _pin 'high to low endEdge := %001 << 6 | _pin 'low to high else 'bad argument for polarity pulse := -1 return asm getct timeOut add timeOut, _timeout setse1 startEdge setq timeOut waitse1 wc if_c jmp #timed_out getct timeOut add timeout, _timeout setse1 endEdge getct startTime setq timeOut waitse1 wc getct pulse if_c jmp #timed_out2 sub pulse, startTime jmp #done timed_out mov pulse, #2 neg pulse jmp #done timed_out2 mov pulse, #3 neg pulse done endasmSorry, my confusion is whether 'drvl _pin' sets the tri-state or if 'dirl _pin' is needed.Thanks for responding,
dgately
PUB PulseinClk(_pin,_polarity,_timeout) : pulse | timeOut, startTime, startEdge, endEdge '' Measures a single pulse and return the length of the pulse in clock ticks or an error flag '' Input parameters: _pin A pin number 0-63. Pins 58-63 for advanced users '' _polarity 1 for a high pulse, 0 for a low pulse '' _timeout Time in clock ticks to wait for an edge '' Output: Pulse length in clock ticks '' Error outputs -1 for _polarity not in (0,1) -2 timed out on start edge -3 timed out on end edge if _polarity == HIGH_PULSE startEdge := %001 << 6 | _pin 'low to high endEdge := %010 << 6 | _pin 'high to low '****** do i need a fltl here ?? elseif _polarity == LOW_PULSE startEdge := %010 << 6 | _pin 'high to low endEdge := %001 << 6 | _pin 'low to high '****** do i need a flth here ?? else 'bad argument for polarity pulse := -1 return asm getct timeOut add timeOut, _timeout setse1 startEdge setq timeOut waitse1 wc if_c jmp #timed_out getct timeOut add timeout, _timeout setse1 endEdge getct startTime setq timeOut waitse1 wc getct pulse if_c jmp #timed_out2 sub pulse, startTime jmp #done timed_out mov pulse, #2 neg pulse jmp #done timed_out2 mov pulse, #3 neg pulse done endasmThis is the routine in pins2.spin2 that may need to be changed. I will try to check this out later.
John Abshier
pins.PulseoutUs(Pin,HIGH,5) asm dirl Pin endasm microSeconds := pins.PulseinUs(Pin, HIGH, timeOut)This change allows the pulse to show up on the pin, but the Ticks function returns a really low value of microseconds for the width of that pulse. Logic is giving a value like: .324 ms when an object is about 80 millimeters from the Ping. The Ticks code is returning the number 3.Thanks Phil and thanks John for taking a look,
dgately
John Abshier
I'm getting realistic results now... I'll test the other functions of Pins2.spin2 as well!
Thank you,
dgately