1. Thank you for confirming that the pot is for changing frequency. I looked closely and found that it seems to be inductor coil outside and perhaps a moving iron core inside, so adjust the frequency around 433MHz.
2. So I think I should not try to turn the pot, because the pot should be adjusted at factory to make sure both transmitter and receiver are tuned at the same frequency. This means that all the xmit/recv pairs sold might have slightly different frequencies and one recv would only worked for one xmit module but not the other.
3. This is very useful for me, because I am thinking of one pico control two pairs of xmit and recv modules.
4. The setup you see is actually a Pico 4WD with BLDC motors. My dream is to train a team of say eight, 4WDs which can talk to each other in RF, sort of forming a team of robot cars, ... But I am diverting too far, let us go back to normal business, ... :)
5. Yes, it would be nice if you can test using Rpi3/4B x 1, Pico x 1, or Pico x 2, and so on. I am too lazy to test with Pico x 2, so think Pcio x 1, with TxD pretending to be Xmit module, and RxD pretending to be another Pico' RxD.
6. About the 3 to 5V level converter: (a) The spec said the Xmit module must be powered by 5V, so 3V3 won't do. (b) Other Arduino guys say they even use higher voltage, up to 12V, and higher the longer distance. For now I will be using 5V, because all the robots are moving on a table. I once thought of using BlueTooth, but that is muc more complicated than the quick, dirty, cheap MX05V.
7. If you do power the xmit module FS1000S with 5V, and you use Pico's GP pin as TxD or output to FS1000S, there would be risk of frying the Pico. One Arudino guy suggests to use a protecting 1K or 10K in series, that should be practical, but there is stall a risk of say 5% or frying the Pcio, because of the so called "Latch up" problem.
8. I just test a level shifter called TXB0104 (CJMCU401) but found a problem, the shifter do shift up signals from 3V to 5V, but once loaded by the FS1000S, the shifter does no longer work and goes into oscillation. I need to find the better, stronger HCT125, but I am too lazy for now, so I will skip the level shifter, and let Pico direct drive the FS1000S. You might like to let me, the brave guy, try this first, and if my Pcio does not fry, then you can follow. :)
I remember that Pcio VBUS had 5V, but am not familiar with Pico power bus, so I am only using external 3V3, 5V0 PSUs.
Now my test results with the CJMCU401/TBX0104 level shifter. As said earlier, no load performance is OK, but troulbe once load with FS1000S. These shifters are mainly for I2C devices with sort of open collector/source cct, and do not work well with push/pull ccts. Anyway, I would try HCT125 later, ...
BTW, I have a newer version of the loopback program, for easier scope waveform display.
# mx05v05.py MX05V, FS1000S 433MHz Demo Program v0.5 tlfong01 2021oct24hkt2143
# Pico GP Pin Assignment
# GP0 = UART0 TxD = MX05 433MHz Revciver Module Data Pin
# GP1 = UART0 RxD = FS1000D 433MHz Transmit Module Data Pin
# Setup
# To loop back, short TxD pin to RxD pin
from machine import UART, Pin
import utime
uart0 = UART(0, baudrate = 9600, tx=Pin(0), rx=Pin(1))
def testUartLoopBackV01():
print('Begin testUartLoopBackV01(), ...')
testMsg = 'Hello World'
print(' writeTestMsg =', testMsg)
Discussion between tlfong01 and Antifa
