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ENG-CANSAT-PICO-MISSION1-CAPTURE (voir la source)

Version du 26 novembre 2022 à 14:43

5 807 octets ajoutés ,  26 novembre 2022 à 14:43
→‎Wire the radio module
Ligne 44 : Ligne 44 :  
|-
 
|-
 
| MOSI
 
| MOSI
−
| GP7 (Miso)
+
| GP7 (Mosi)
 
|-
 
|-
 
| MISO
 
| MISO
−
| GP4 (Mosi)
+
| GP4 (Miso)
 
|-
 
|-
 
| SCK
 
| SCK
Ligne 84 : Ligne 84 :  
Finally wire the RFM69HCW radio as follows
 
Finally wire the RFM69HCW radio as follows
   −
[[Fichier:ENG-CANSAT-PICO-RFM69HCW-to-Cansat-Pico-Base.jpg|640px]]
+
[[Fichier:ENG-CANSAT-PICO-RFM69HCW-to-Cansat-Pico-Base-fixed.jpg|640px]]
    
{| class="wikitable"  
 
{| class="wikitable"  
Ligne 103 : Ligne 103 :  
| keep the same pin as receiver.<br />Otherwise use UEXT 10 (=gp10)
 
| keep the same pin as receiver.<br />Otherwise use UEXT 10 (=gp10)
 
|-
 
|-
−
| MOSI
+
| MISO
 
| 7
 
| 7
 
|  
 
|  
 
| GP4 = MISO
 
| GP4 = MISO
 
|-
 
|-
−
| MISO
+
| MOSI
 
| 8
 
| 8
 
|  
 
|  
Ligne 132 : Ligne 132 :  
The code is available for download on the [https://github.com/mchobby/cansat-belgium-micropython GitHub associated to this wiki].
 
The code is available for download on the [https://github.com/mchobby/cansat-belgium-micropython GitHub associated to this wiki].
   −
{{download-box|Téléchargez Mission1 Cansat Emitter script (cansat.py)|https://raw.githubusercontent.com/mchobby/cansat-belgium/master/mission1/cansat.py}}
+
{{download-box|Téléchargez Mission1 Cansat Emitter script (cansat.py)|https://github.com/mchobby/cansat-belgium-micropython/blob/main/mission1/cansat.py}}
    
Without any comments, extra lines and print statement (used to debug), the script makes 33 lines long for the full fledged features.
 
Without any comments, extra lines and print statement (used to debug), the script makes 33 lines long for the full fledged features.
Ligne 201 : Ligne 201 :  
[[Fichier:ENG-CANSAT-PICO-MISSION1-CAPTURE-25.png|360px]]
 
[[Fichier:ENG-CANSAT-PICO-MISSION1-CAPTURE-25.png|360px]]
   −
The {{fname|cansat2.py}} script do re-enforce error controls with {{fname|try...except}} statements in the script and showing various onboard LED patterns in case of error.
+
The [https://github.com/mchobby/cansat-belgium-micropython/tree/main/mission1 cansat2.py] script do re-enforce error controls with {{fname|try...except}} statements in the script and showing various onboard LED patterns in case of error.
    
Error Code are reported as quick serie of blink following by slow blink... counting the slow blink gives the error code number.
 
Error Code are reported as quick serie of blink following by slow blink... counting the slow blink gives the error code number.
Ligne 211 : Ligne 211 :  
| align="center" | Fix the issue
 
| align="center" | Fix the issue
 
|- style="font-size: 90%"
 
|- style="font-size: 90%"
−
| align="left" | Continuously Off
+
| align="left" | OFF (continuously)
 
| align="left" | No code is running/started.
 
| align="left" | No code is running/started.
 
| align="left" | Check that cansat code is called/executed from main.
 
| align="left" | Check that cansat code is called/executed from main.
Ligne 236 : Ligne 236 :  
|}
 
|}
    +
== The code explained ==
 +
Here some explanation about the {{fname|cansat.py}} script used in the CanSat.
 +
 +
This MicroPython script would:
 +
* Initialize the buses and hardware
 +
* Collect the sensor data
 +
* Send it over the USB-serial connection
 +
* Send it over the radio link
 +
 +
First, the script will includes all the needed libraries.
 +
 +
<syntaxhighlight lang="python">from machine import SPI, I2C, Pin, ADC
 +
from rfm69 import RFM69
 +
from bme280 import BME280, BMP280_I2CADDR
 +
import time
 +
</syntaxhighlight>
 +
 +
This section is immediately followed by the various CONSTANT used in the script.
 +
 +
<syntaxhighlight lang="python">FREQ          = 433.1
 +
ENCRYPTION_KEY = b"\x01\x02\x03\x04\x05\x06\x07\x08\x01\x02\x03\x04\x05\x06\x07\x08"
 +
NODE_ID        = 120 # ID of this node
 +
BASESTATION_ID = 100 # ID of the node (base station) to be contacted
 +
</syntaxhighlight>
 +
 +
{{dbox-orange|Don't forget to update the radio frequency '''FREQ''' and the '''ENCRYPTION_KEY''' encryption key. }}
 +
 +
=== Creating ressources ===
 +
Then we create the needed buses resources to access the various sensor.
 +
 +
<syntaxhighlight lang="python">spi = SPI(0, baudrate=50000, polarity=0, phase=0, firstbit=SPI.MSB)
 +
nss = Pin( 5, Pin.OUT, value=True )
 +
rst = Pin( 3, Pin.OUT, value=False )
 +
i2c = I2C(0)
 +
</syntaxhighlight>
 +
 +
Next we create the RFM69 radio object (named {{fname|rfm}}) and the BMP280 radio object (named {{fname|bmp}}).
 +
 +
<syntaxhighlight lang="python"># RFM Module
 +
rfm = RFM69( spi=spi, nss=nss, reset=rst )
 +
rfm.frequency_mhz  = FREQ
 +
rfm.encryption_key = ( ENCRYPTION_KEY )
 +
rfm.node          = NODE_ID # This instance is the node 120
 +
rfm.destination    = BASESTATION_ID # Send to specific node 100
 +
# BMP280 (uses the BME280)
 +
bmp = BME280( i2c=i2c, address=BMP280_I2CADDR )
 +
</syntaxhighlight>
 +
 +
At the end of initialization section, we do creates the instances for the analog reading (the TMP36, named {{fname|adc}}) and LED controling (named {{fname|led}}).
 +
 +
<syntaxhighlight lang="python"># TMP36 analog pin
 +
adc = ADC(Pin(26))
 +
# Onboard LED
 +
led = Pin(25, Pin.OUT)
 +
</syntaxhighlight>
 +
 +
=== Information logging ===
 +
 +
Just before the main loop, the script print the essential data.
 +
 +
<syntaxhighlight lang="python"># Main Loop
 +
print( 'Frequency    :', rfm.frequency_mhz )
 +
print( 'encryption    :', rfm.encryption_key )
 +
print( 'NODE_ID      :', NODE_ID )
 +
print( 'BASESTATION_ID:', BASESTATION_ID )
 +
print( '***HEADER***' )
 +
print( ":iteration_count,time_sec,pressure_hpa,tmp36_temp,bmp280_temp;" )
 +
print( '***DATA***' )
 +
</syntaxhighlight>
 +
 +
=== Main Loop execution ===
 +
The main loop is composed of an infinite {{fname|while}} loop.
 +
 +
<syntaxhighlight lang="python"># Iteration counter
 +
counter = 1
 +
# ctime contains the time (in seconds) when the script was stared
 +
ctime = time.time() # Now
 +
while True:
 +
    # Main Loop body
 +
    ...
 +
    ...
 +
    ...
 +
    counter += 1    # increment iteration counter
 +
    time.sleep(0.4) # wait 0.4 second between iterations
 +
</syntaxhighlight>
 +
 +
The '''Mainloop body''' executes the following steps:
 +
# Reading the sensors data
 +
# Preparing the message
 +
# Sending message
 +
## Switch on the onboard LED
 +
## Log message
 +
## Send message
 +
## Turn of the LED
 +
 +
{{underline|'''Reading sensor data:'''}}
 +
 +
Reading the BMP280 sensor data relies on the {{fname|bme280.py} library previously detailled.
 +
 +
Reading the temperature from TMP36 relies on analog reading and some conversion calculation.
 +
 +
<syntaxhighlight lang="python"># read BMP280
 +
t,hpa,rh =  bmp.raw_values # Temp, press_hPa, humidity
 +
# Read tmp36 (analog)
 +
value = adc.read_u16()
 +
mv = 3300.0 * value / 65535
 +
temp = (mv-500)/10
 +
</syntaxhighlight>
 +
 +
Next the mainloop do prepare the string message (variable {{fname|msg}} by using the powerful Python string formatting feature.
 +
 +
{{underline|'''Formatting data:'''}}
 +
 +
This can be done with one single line. Notice the expression {{fname|time.time()-ctime}} calculating the elapse time (in second) since the mainloop started. 
 +
<syntaxhighlight lang="python"># message: iteration_count,time_sec,pressure_hpa,tmp36_temp,bmp280_temp (coma separated)
 +
msg = ":%i,%i,%6.2f,%5.2f,%5.2f;" % (counter,time.time()-ctime,hpa,temp,t)
 +
</syntaxhighlight>
 +
 +
{{underline|'''Sending data:'''}}
 +
 +
The onboard LED is switched on during data transmission (and print). This makes the LED flashing briefly while data us transmitted.
 +
 +
The data packet are sent without ACK, this would avoids unnecessary latency by waiting for ACK. Indeed, the Cansat will not modifies its behaviours if the data are not received on the ground station.
 +
 +
<syntaxhighlight lang="python">led.on() # Led ON while sending data
 +
print( msg )
 +
# Send a packet without ACK - Send it, don't care if it is received or not
 +
rfm.send(bytes(msg , "utf-8") )
 +
led.off()
 +
</syntaxhighlight>
 +
 +
Just to remind, the {{fname|rfm.send()}} only accepts binary data as generated with bytes() or bytearray(). The message string must be converted to a binary with {{fname|bytes()}}. As binary data does not accept value > 127 without a proper encoding then the bytes() conversion must identifies the encoding of the source string to applies the adequate encoding scheme (UTF8 -> Binary).
 +
 +
== Fault tolerant design ==
 +
The goal is to transmit the data to the ground station.<br />The code of the Cansat Emitter (this section) and Receiver BaseStation (next section) are doing the job.
 +
 +
However, what would happens to your data if the antenna did break? All the data are lots!
 +
 +
This is where the "[[ENG-CANSAT-PICO-LOG|Data Logging]]" would be a great help!
 +
 +
As showed earlier, it is also possible to store/save the data into the MicroPython FileSystem (the Flash).
 +
 +
A good approach would be:
 +
# to save the data in the file
 +
# then send it over Radio.
    +
In this way, the data stays available inside the CanSat and could be readed as suited.
    
{{ENG-CANSAT-PICO-TRAILER}}
 
{{ENG-CANSAT-PICO-TRAILER}}
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Récupérée de « https://wiki.mchobby.be/index.php?title=Spécial:MobileDiff/30433...30968 »

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