FMS Forum

by **cyberguy** » Thu Nov 13, 2003 7:23 am

Hi,

I made 16F84 type interface both Eric's schematics and also from FMS Doc. I'm using PIC chips for a long time. I used my scope for measuring signal input and output on both device. The problem is on FMS device when I turned off my transmitter on the Eric's test program little dots are moving up-left corner. When I turned on I can see some numbers on the screen and dots are moving bottom-right corner. After all nothing happens. When I click calibrate I cannot see anything. But when I touch transmitter antenna sometimes I'm getting flicky numbers and dot's are moving in the box. I tried this 2 different computer one of them is notebook and the other is desktop. Voltages are ok on Vcc and PIC legs. Also I can read nearly +/- 9 v on DSUB. So if someone can give me some advise I appriciate.

by **Eric Brouwer** » Thu Nov 13, 2003 12:17 pm

There can be several things that can cause this. Check the following:

- Is the configuration bits of the PIC set correct during programming ? (HS, WDT On, the others does not matter).

- Is the PIC actually running? Have a look at the crystal (4MHz) and capacitors (15p).

- Is your transmitter selected to PPM mode. The PIC interfaces does not function in PCM modes.

- What type of transmitter are you using? JR transmitters have a very low output signal (< 1V). The input circuit should be modified as on my web to function correct with JR transmitters.

- Does your interface receive the correct voltage from the serial port? You should measure around 4 - 5 V across the PIC supply (pin 5 & 14).

- Did you use the correct transistors in the circuit. The input circuit should have a NPN transistor, and the output circuit (serial port side) a PNP. Also, note that the emitter of the PNP transistor is connected to +5V and not 0V.

- There are some newer PC's that either does not have high enough voltage levels on the serial ports to power the interface, and an external power supply will be required.

- Another problem (1 out of about 100) is PC's which requires voltage levels higher than +5V on the Rx pin (pin 2 on serial port) to work correct. For this, an external powwer supply as well as a RS232 converter will be required to raise the serial data signal to +10V. For more details, please contact me direct.

If everything else fails, you are more than welcome to send your interface to me so that I can have a look at it.

by **cyberguy** » Thu Nov 13, 2003 5:45 pm

hi,

Thanks for quick answer. I'm using Futaba skysport 4. I believe I programmed PIC correctly because I'm familiar with PIC's I made couple different devices with PIC interface. On the other hand I'm using notebook and desktop. Of course notebook power is not enough for this device teherfore I'm using my Compaq desktop. I can measure 4.86 V between GND and PIC 14th pin and PNP BC557 emitter leg. Also I measure -9.6 v on DSUB 4th leg and 9 V on DSUB 2 and 7th legs.. As I said system can sense some signal when I turned off and on my transmitter. But after that I'm not able to calibrate because I cannot see any number on PPMIn Min Max colums

by **cyberguy** » Thu Nov 13, 2003 6:45 pm

Hi Eric,

Something happened strange now. I want to apply external power to the device and I remove 7th pin connection of DSUB from PCB and suddenly I saw numbers on the test program. Now it's working that compicated

)) device. But when I aplly 7th leg back it cannot work but when I apply 12 v from desktop power supply it's ok. Any commands . Thanks anyway for your support and helping us. Cheers

by **cyberguy** » Thu Nov 13, 2003 6:47 pm

Correction for 12 v . when I apply 12 v again it's not working now I just disconnet 7th pin from my device everythings are ok

by **hasenhittel** » Tue Dec 23, 2003 1:49 pm

Hello,

we have the same problem. Since several days we are looking what could be wrong. If you disconnect Pin7 how is your interface provided with power? Did you use an external power supply?

Hasenhittel

by **tomcat** » Sat Apr 17, 2004 9:20 pm

woderfull, thanks to cyberguy.....
I had the same Problem, I will try it tomorrow what happens when i remove pin 7 from subD.
My Radio Control is a Futaba FX 18.

by **tomcat** » Mon Apr 19, 2004 12:37 pm

now I am a little bit confused !!!
I try to disconnect pin 7 from subD, but it will work nothing.
I connectet it again on Pin7.
Now i see in "Pic test"(Set on 9600) verry confused Numbers, and the balls in the cube will went up and down, like to see 2 or more balls.
I start FMS , set it to pic controller, but not on 9600(there it will do nothing).
with 19200 it will works fine.
My system is win XP.
whats wrong???

by **Eric Brouwer** » Wed Apr 21, 2004 7:28 pm

Well, without power, I also do'nt know how the circuit can be operating, unless the PIC gets some voltage via pins 2 or 4.

Please note that most PIC interfaces works on 19200 baud, explaining the unstable values in the test software.

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PIC Interface problem - Cannot see numbers...

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