Testing Ronja Tetrapolis

We are going to test the electronics. You should get to the end without problems. If there is a bug and you can't identify it and repair it, ask on the mailing list.

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Powering Tetrapolis for the first time

Now connect Twister2, receiver and transmitter according to the picture with power removed. Plug power into Twister2. Check if the yellow light is shining. If not, disconnect power immediately and there is an error. If you want, desolder one wire from the power DE9 connector and measure the power consumption (typical values):

Idle with receiving 1MHz idle signal	185mA
Full data load (both directions)	225mA

Check of measurement points

Check all voltage measurement points except current one, because for measuring a current you have to break the circuit. Measurement points are those small tables in the schematics with various variables. Check the values in receiver and transmitter. Determine if the measured voltages are in the specified range. The voltages are measured against ground (i. e. the tin of the can). All points should be OK. If they are not, perform once more correctness check of the affected module. If the problem persists, ask on the mailing list.

Testing RSSI operation

Check whether the TX diode shines. Connect 200mV voltmeter into Receiver's RX level DC measurement (Received Signal Strength Indicator, RSSI). Check whether the multimeter readout reacts to the light strength from the transmitter.

Preemphasis setting

Do preemphasis test of Tetrapolis. Change value of R8 according to the result:

Result	Action
LED shines too long	Increase R8
LED shines too short	Decrease R8
OK	Done

LED current setting

Let the transmitter shine without sending any packets into it. Measure DC voltage U across R11 (default valu 8R2) and then switch off the transmitter completely by plugging the Twister2 out of power. Measure the real value R of the R11 (default nominal value 8R2). Calculate the DC current I flowing according to Ohm's law as I=U/R. If the is greater than 68mA, replace R11 (8R2) with R14 (10). Reconnect the power of Twister2 and continue with testing by sending ping's.

Performance Measurements

Do at least one from the following Tetrapolis tests (if you don't have prerequisites for one, then go to another etc.):

If something is wrong

If you are getting substantially smaller ranges (for example 0.7m for SFH203), something is wrong.

The input transistor of the receiver (Q101, BF908 or its equivalent) can be broken-through. It is caused by inappropriate handling: the device is static electricity sensitive. It can be caused also by soldering with an iron with ungrounded tip or transformer soldering gun can generate spikes during switching. This sometimes manifests as a voltage greater than 0V on P103. My healthy receiver has 0.1mV on P103.

A breakthrough of G2 sometimes manifests itself as a receiver that is oscillating (doesn't work at all or has inferior range) where the oscillations cease when C103 is removed from the circuit.

Breakthrough of Q101 can be fixed only by replacing with another one and obeying the rules for manipulation with static electricity sensitive devices.

Range reduction

If you plan to use Ronja on a link less than 1/4 of nominal distance, then perform range reduction now.

Mount Thermal Shields

Now mount the thermal shields to both the receiver and transmitter using four M3x10 screws and 12 M3 nuts. Tighten it all together firmly.