Active low transmitter question

[LEDave]

Hi Ioannis - I came across this short instructional / demo video for anyone else who's interested in this topic, simple video but shows Tx/Rx in action. It's not the exact same model as the ones I've now ordered but very similar, you may have to scroll down the page a tad to see the video.


http://www.rfsolutions.co.uk/radio-m...ule-1000m-p378

[LEDave]

Sorry guys another question from me.

The demo video shows a lady pressing a push button to ground on Tx Input pin1, which on the Rx latches an led on, so:

How do I mimic a 'single' button press to ground on Tx Input pin1 from a pic? do I:

Just set GPIO.0 = 0 'Pulls Tx pin1 LOW causes a Tx
then set GPIO.0 = 1 'pulls Tx pin1 High, from data sheet Tx Inputs pins are internally pulled high anyway
Or would the above cause two Tx's

Or do I:

Set GPIO.0 = 0 'Pulls Tx pin1 LOW causes a Tx
Then Change TRISIO = %00000001 'Set bit.0 to input and mimic a floating open switch Tx Inputs pins are internally pulled high

[richard]

The demo video shows a lady pressing a push button to ground on Tx Input pin1, which on the Rx latches an led on, so:

yes on a different device to what was previously discussed and not to mention the woefully inadequate description of the hardware
is the switch momentary or latching ?

if the switch is momentary then the operational description in the data sheet completely fails to explain the toggle action
occurring

consult the salesman

[LEDave]

Ok, ignoring the video and the different device and back onto this one.


How do I mimic a 'single momentary' button press to ground on Transmitter Input pin1 using a pic instead of a button? do I:

Set TRISIO = %11111110 'set bit 0 to output
Then set GPIO.0 = 0 'Pulls Tx pin1 LOW causes a Tx
Pause 50ms 'Alow time for Tx
Then set GPIO.0 = 1 'pulls Tx pin1 High, from data sheet Tx Input pins are internally pulled high anyway
Or would the above cause two Tx's (two state changes).

Or do I:

Set TRISIO = %11111110 'set bit 0 to output
Then set GPIO.0 = 0 'Pulls Tx pin1 LOW causes a Tx
pause 50ms 'Alow time for Tx
Then Change TRISIO = %00000001 'Set bit.0 to input and mimic a floating open switch, Tx Input pins are internally pulled high (data sheet)
And then when I want to Tx again set the TRIS bit 0 then GPIO.0 LOW etc.

[richard]

if an input pin on the module distinguishes between a high impedance high and a low impedance high then
its not a normal LVCMOS/LVTTL logic input , the datasheet has not described such a capability.

Pause 50ms 'Alow time for Tx

the datasheet does not specify this need ,the min tx time is 55ms anyway isn't it ?
the datasheet does not specify a min hold/reaction time at all that i can see

no point guessing ---- consult the salesman

[LEDave]

if an input pin on the module distinguishes between a high impedance high and a low impedance high then
its not a normal LVCMOS/LVTTL logic input , the data sheet has not described such a capability.

no point guessing ---- consult the salesman ---- Will do later today if possible and get back.

Just to help me - Data sheet says:

Inputs are internally pulled high, active low

Ok - This is my understanding / misunderstanding of how these things work - Please tell me which of these statements is correct / incorrect so that I can learn.

A/ INPUTS are high impedance 'Z' state (floating)
B/ 'Z' state could be anywhere from High to Low unless pulled into a High/Low state via a resistor(10k)
C/ OUTPUTS are just High / Low

Data sheet for Transmitter says 'Input internally held high' (So an internal pullup resistor to +v) and then pulled low via push button or in my case a Pic, this will cause a Tx, Lora Mode 5 is the Tx default (720ms) not sure if I hold Tx Input pin low for this length of time, another question for the sales guy I guess.

[richard]

A/ INPUTS are high impedance 'Z' state (floating)

no, INPUTS are always high impedance , there is no "high Z" state for digital inputs and they should be pulled into a High/Low state via a resistor so as not to float if left unconnected and they are active

B/ 'Z' state could be anywhere from High to Low unless pulled into a High/Low state via a resistor(10k)

hmmm. high z is high z its not an output

C/ OUTPUTS are just High / Low

no outputs are what you could tristate (high z) to stop that pin from loading a shared bus inappropriately
otherwise they are just High / Low if loaded correctly.

Data sheet for Transmitter says 'Input internally held high' (So an internal pullup resistor to +v) and then pulled low via push button or in my case a Pic, this will cause a Tx, Lora Mode 5 is the Tx default (720ms) not sure if I hold Tx Input pin low for this length of time, another question for the sales guy I guess.

pure speculation , i believe the demo totally misleads by not specifying if the sw is push on / push off or momentary.
there is no mention of debouncing , rearming time or several other things

\

[NickSaggy]

Did they get the issue handled. It was always frustrating.