The problem
I tried to find reliable information on the range of the ESP-12 series modules, but was not quite happy with what I found. Neither the use of highly directional antennas (or is it "antennae"?) nor the selection of client devices seemed right to draw conclusions about the actual range.EDIT: see the 1st part of my video about the tester here.
EDIT: and here is the 2nd part if the video with the results
The idea
ESP-8266 modules at both ends of the connection seemed like a good idea to me. Normally you would use a simple ping-test to see if packets are lost on the way between the modules.ICMP
Despite the fact that the LWIP stack in NodeMCU does handle ICMP properly, I have yet to see a "Ping" program to send/revceive ICMP echo-requests/replies.TCP
TCP connections between two NodeMCU endpoints are super easy. But the TCP protocol will do it's best to compensate the loss of packets, so we wouldn't detect missing packets until the connection breaks up completely.UDP
UDP does not provide such a recovery mechanism for lost packets, so the application has to handle that. We can use that easily to find out when packets go missing.The solution
Ok, so UDP it is. We'll simply connect an ESP-12e module in station-mode to an ESP-12f module in soft-ap mode and send UDP packets from the ESP-12e to the ESP-12f module.The payload of each packet is a numer that is incremented by one for each packet. So if a packet is missing, it is easy to detect.
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| The ESP-modules |
What you need
- the server.lua script (to put on the module with the OLED)
- the client.lua script
- Geekcreit-Doit Dev-board (the smaller one with the ESP-12f module)
- The classic V3-NodeMcu-Lua-WIFI-Development board (with ESP-12e module)
- Two USB Power banks like this one or that one
- breadboard
- dupont jumper wires (male/male)
The server.lua script
local LED_PIN1 = 4
gpio.mode(LED_PIN1, gpio.OUTPUT)
local sw1 = true
wifi.setmode(wifi.SOFTAP)
cfg={}
cfg.ssid="AReResearch"
wifi.ap.config(cfg)
function init_OLED(sda,scl)
sla = 0x3c
i2c.setup(0, sda, scl, i2c.SLOW)
disp = u8g.ssd1306_128x64_i2c(sla)
disp:setFont(u8g.font_6x10)
disp:setFontRefHeightExtendedText()
disp:setDefaultForegroundColor()
disp:setFontPosTop()
end
init_OLED(5,6)
err=0
cold=1
disp:firstPage()
repeat
disp:drawStr(0, 10, "AReResearch UDP-Ranger")
disp:drawStr(5, 35, "Waiting for client...")
until disp:nextPage() == false
s=net.createServer(net.UDP)
s:on("receive",function(s,c)
print("Sequence="..c.." Previous:"..cold)
if ((cold+1)~=tonumber(c)) then
err=err+1
end
disp:firstPage()
repeat
disp:drawStr(0, 10, "AReResearch UDP-Ranger")
disp:drawStr(5, 35, "Packet Nr:" .. c)
disp:drawStr(5, 45, "Errors:" .. err)
until disp:nextPage() == false
if (sw1) then
gpio.write(LED_PIN1, gpio.LOW)
else
gpio.write(LED_PIN1, gpio.HIGH)
end
sw1 = not sw1
cold=c
end)
s:listen(8888)
The client-lua script
wifi.setmode(wifi.STATION)
wifi.sta.config("AReResearch","")
wifi.sta.connect()
LED_PIN1 = 4
gpio.mode(LED_PIN1, gpio.OUTPUT)
print (wifi.sta.getip())
x=1
tmr.alarm(2, 1000, 1, function()
conn = net.createConnection(net.UDP, 0)
conn:connect(8888,"192.168.4.1")
conn:send(x)
conn:close()
conn = nil
x=x+1
print (x)
if x>1000 then x=1 end
p=tonumber(wifi.sta.status())
print (p)
if p == 5
then
gpio.write(LED_PIN1, gpio.LOW)
print ("LED OFF")
else
gpio.write(LED_PIN1, gpio.HIGH)
print ("LED ON")
end
end)
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| Start the "server"module first |
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| The "client" has sent packets |
How to use this
Once the client module has connected to the "server", the server module's LED will be toggled every time a packet is received. More info in how many packets have been missed is shown on the OLED.So it is easy to tell when the connection starts breaking up.
