Can't getting access to WT32 bluetooth module

Wireless & IoT
1

Dear collegues,

i have a problem with my WT32 bluetooth module from bluegiga.

By connecting a PC through RS232 over a MAX232 and a 3.3V-Zener-Diode (for reducing the 5V output voltage of the MAX232 to 3.3V) I don’t get an answer from my module.

I have following settings in the hyperterminal:

  • 115200 baud

  • no parity

  • 8 databits

  • no flowcontrol

  • 1 stopbit

I already checked the signal line RXD with the oscilloscope and I can see that the voltage is drawn down when pressing a button in hyperterminal.

Eagle-Schematic from my circuit:

http://www.bilder-space.de/show.php?fil … wCdMZt.JPG

The iWRAP firmware of the bluetooth module doesn’t show me its greeting notice.

Does anybody know how to solve my problem so that I can get access to the module?

Greets,

Mike

2

I would try disconnecting the reset line from ground.

Here’s what the manual says:

WT32 has an internal reset circuitry, which keeps the reset pin active until supply voltage

has reached stability in the start up. This ensures that supply for the flash memory inside

the WT32 will reach stability before BC4 chip fetches instructions from it. Schematic of the

reset circuitry is shown in figure 3. Rising supply voltage charges the capacitor, which will

activate the reset of WT32. The capacitor discharges through 220 k resistor, which

eventually deactivates the reset. Time constant of the RC circuitry is set in a way that the

supply voltage is safely stabilized before the reset deactivates. Pull-up or pull-down

resistor should not be connected to the reset pin to ensure proper start up of WT32. If the

reset pin of WT32 is in use, the designer should verify that WT32 remains in reset during a

start-up until all supply voltages have stabilized.

3

I tried it now with reset floating but I dont get a reply from the module…

any other ideas?

thx

4

If it was me, I would use a MAX3232 instead of the Max232, run the whole circuit on 3.3V, and get rid of the resistor and zener in the receive line. Also, you might want to try connecting RTS to CTS instead of grounding the pin.

Also, from the manual:

VDD_BAT

Input for an internal 1.8 V switched mode regulator combined with output of the internal

battery charger. See chapter 5.3 for detailed description for the charger. When not

powered from a battery, VDD_IO and VDD_BAT can be combined to a single 3.3 V supply

voltage.

This would seem to indicate that this needs to be tied to 3.3V also.