Flow Control Issues

BCISS

Im having a problem displaying information from my device (LinkMatik 2.0). The only help I've gotten from their support team is:

To check the flow control, verify the voltages on TxD, RxD, CTS, RTS are as you would expect. (CTS, RTS low, TxD, RxD high.) Use a scope or LED to check whether data is actually transmitted on TxD, RxD.

All of the pins are set correctly (CTS/RTS - low ; TxD/RxD - high), however I do not see any changes when I check whether data is transmitted on TxD/RxD via LEDs. My baud rate is set to 9600bps, so I assume I cannot see the pins going high and low? How do I check whether my device is receiving data via the serial port?

Regards,
BCISS

Phil Pilgrim (PhiPi)

I assume the four lines you mention are at logic levels, given their default polarities. That being the case, attach an LED from Vdd to the receive data line, through a 470-ohm resistor. The LED will light whenever there's serial data on that line. If the data is sparse, you may need to cup your hands around the LED to see the pulses.

-Phil

BCISS

We set up the example you described, but saw no change in the LED.· The LED would·be unlit·(Vdd & RxD both high); when data was sent thru the hyperterminal it appeared that there was no change in RxD voltage level (Vdd & RxD both high still).

Here is how we set up the circuit

Vdd -- R(470 Ohm) -- Diode -- RxD

We also tried slowing the baud rate to 300 bps, just to see if we could slow down the data transmission, but still nothing.

Taurusboy

hi may I know wat is the programming code? mine is as follows:

example = 90

SEROUT TxPin\CTSPin, BaudM, [noparse][[/noparse]DEC example, TAB,CR]

By right,

90

should be shown on my Hyper Terminal right? MayI know if my programming code is wrong? Also, how do I write the receiving programming code?

SERIN RxPin\RTS, BaudM, [noparse][[/noparse]example]

by right, i should receive the value 90 and it will be stored in VAR example right?

Bruce Bates

Taurusboy -

You have one thing missing. You neglected to define the variable "example", thus it doesn't exist. If it is one byte, then you can declare it this way at the beginning of your program:

example VAR BYTE 'Maximum value 255

If it is a WORD (two bytes) you can define it this way:

example VAR WORD 'Maximum value 65535

Then you can go ahead and set it to any initial value you want, within the above noted range limitations.

Regards,

Bruce Bates

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