Mar 14, 2013

Robot project Wifi - Tortured TP-Link MR3020

I planned a robot controlled by wireless from a smartphone or a PC. The basis of this robot is a very economical router TP-Link MR3020.

But then, I have to connect to this router:
  • Where an arduino will be connected motors ( servos modified ) and sensors.
  • A basic webcam (Logitech CZ110).
At first I was thinking of adding a USB connector on the microprocessor has probably the router, as I had done some time ago on a Netgear router . But then, the microprocessor datasheet is not public and its "form factor" makes it very difficult to hack.

You say, a usb, enough for the webcam. Except that the router has only 4MB of flash memory which makes it impossible to add software like python and mjpeg-streamer. So add additional memory. To this add 2 possibilities: 1 MMC used with GPIO lines or 1 SD / USB-key. The GPIO lines are few (except to remove switches and LEDs) I opted for the USB drive and a μSD. I will also use two GPIO lines in I2C to communicate with the arduino.

I bought a USB hub STOREX 3€ to disassemble and retrieve its PCB. Unfortunately, the self-powered hub is not yet consumption of the camera + SD is very limited we will be remedied by plugging the power on the USB hub.

Come on, hop on the box apart is stuck. Only card interest. Power is useless in this project, we will put it aside for later.

The USB Hub
The power plug must be removed and the USB connectors to save space and weight.

USB Hub / Power
Reader μSD €3 is disassembled to easily access USB tracks. It is removed "properly" and then be re-assembled, the carcass of the USB is essential for the maintenance of the map μSD.

μSD reader
The reader can then be soldered directly to the USB hub still in the idea of ​​saving space.

The USB Hub
Then you can re-assemble the drive and stick it on the hub.

The hub and drive μSD
I damaged a few tracks by unsoldering the USB connectors. It must be said that €3, PCB is not worth much ... but it's still the epoxy and not of bakelite.

Now back on the router. To increase its scope quite small, we're going to add an external antenna. Simply remove the shunt in J4 and come weld the cable core antenna on the track next to the registration J4 (1) and the mass of the pad side (2).

External antenna J4
It is small and zooming have clearly seen my big blocks!

Connect the external antenna
Here is the result with the router in its original box.

External antenna and serial console
To avoid damage to the router, I have not unsoldered the USB port. I just soldered directly on the PCB son to connect to the hub. An iron shot and you can make the router to its original function. In addition, at this place, the place occupied by the connector does not bother me.

The camera is fitted with a new connection based barette divisible by 2.54.

The MR3020 his webcam and usb hub
That's it for hardware changes. Following concern research and GPIOs free soft part.

GPIO on the mode selection switch, flikr
Here for example a track. Rather than remove the LEDs that are useful, you can remove the switch mode selection that does not serve us. It will give us our 2 GPIO (1: GND, 2: GPIO 18 & 20) for i2c. But before doing that, I'll see if there is any other useful or useless GPIO bit like his cousin of TP-Link WR703N. - equinoxefr


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