Dialog with Maxbotix EZ0 ultrasonic altimeter

Hello everybody.

I meet a problem of dialog with an ultrasonic radio-altimeter MAXBOTIX LV-MaxSonar-EZ0.

Dialog is not at all as expected in RealTerminal (with my FDTI USB port interface) :

- RealTerminal displays periodic data, but not at all as specified in EZ0 datasheet

- red signal flashs in RealTerminal (dialog error)

even with the std serial link parameters (9600/8/1/N) provided by Maxbotix.

Bob Gross from Maxbotix has answered to me :

"Our sensors output in the RS232 format (but TTL levels) . If you invert the output from
the sensor, it will be read by your device correctly"

I have tried to invert data in RealTerminal but no coherent dialog yet.

Have you ever tried to connect this kind of device directly to FDTI port (or microcontroler UART port) with software data inversion, or do I need a hardware signal inversion between FTDI and EZ0 boards ??? (Grrr !) .

Thanks for your help,

Gilles

(FRANCE)

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Ken April 5, 2010 at 3:54pm

It isn't the bits of just the data payload that need inverted. Also inverted are the stop & start bits, (& partity if you were to use it). You need to invert the actual 5v/0v SIGNAL, not the data received by the CPU. Get yourself a $0.15 inverter or buffer/inverter chip. A 7404 TTL chip or the 4049 CMOS chip should do ya fine.

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Dialog with Maxbotix EZ0 ultrasonic altimeter

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