Unpack and Pack

[MJ]

Hi there, i want to pack a float in the node and send it over to the gateway. May i know is the format valid?

_LORA_PKG_FORMAT = "BBf" #1byte for device_id, 1 byte for package size, 1 for float

Here is the information that i want it to be pack as a float at Node

D = 10**((Measured_power-rssi)/(10*n)
pkg = struct.pack(_LORA_PKG_FORMAT % len(msg), DEVICE_ID, len(msg), D) lora_sock.send(pkg)
Here is the information that unpack at Gateway

device_id, pkg_len, D = struct.unpack(_LORA_PKG_FORMAT % recv_pkg_len, recv_pkg)
I tried this format but i have no received anythings from the node and i tried the example of the Lora Nano-gateway in documentation and it work so i guess is not the firmware problem since i have all lopy updated to the same version.
Any help would be appreciate. Thank you.

[robert-hh]

@mj SInce the for string for pack contains only two fields, it must be written as:

_LORA_PKG_FORMAT = "Bf"
pkg = struct.pack(_LORA_PKG_FORMAT, DEVICE_ID,  D) 

But besides that, the receiver must contains a lora_sock.recv(64) call, in order to get something. Please have a look at the simple examples in the documentation on how the code structure has to be set up.

[MJ]

@robert-hh
I have tried but still showing no response once i uploaded the code.

On my Node :

_LORA_PKG_FORMAT = "Bf"
DEVICE_ID = 0x01
lora = LoRa(mode=LoRa.LORA, tx_iq=True, frequency = 915000000)
lora_sock = socket.socket(socket.AF_LORA, socket.SOCK_RAW)
lora_sock.setblocking(False)
Measured_power = -37
n = 3 
d = (10**((Measured_power-rssi)/(10*n)))/1000

pkg = struct.pack(_LORA_PKG_FORMAT, DEVICE_ID, 6, D)
lora_sock.send(pkg)

For Gateway :

_LORA_PKG_FORMAT = "Bf"
lora = LoRa(mode=LoRa.LORA, rx_iq=True, frequency = 915000000)
lora_sock = socket.socket(socket.AF_LORA, socket.SOCK_RAW)

device_id, D = struct.unpack(_LORA_PKG_FORMAT, recv_pkg)

Is there any mistake? Thank you.

[robert-hh]

@mj said in Unpack and Pack:

pkg = struct.pack(_LORA_PKG_FORMAT % len(msg), DEVICE_ID, len(msg), D) lora_sock.send(pkg)

Since you have a fixed message length, you can simply use:
struct.pack(FORMAT, DEVICE_ID, 6, D)
and unpack with:
device_id, pkg_len, D = struct.unpack(_LORA_PKG_FORMAT, recv_pkg)
You can even omit sending the pkg_len and pack with:

_LORA_PKG_FORMAT = "Bf" #1byte for device_id, 4 for float
D = 10**((Measured_power-rssi)/(10*n)
pkg = struct.pack(_LORA_PKG_FORMAT, DEVICE_ID,  D) lora_sock.send(pkg)

and unpack with:

device_id, D = struct.unpack(_LORA_PKG_FORMAT, recv_pkg)