PDB Max3232 problems

Crosswinds

I'm currently experimenting with some serial comms to a Pc.
Started a prop with a serial Cog, outputting a message every second at 9600, hooked up that pin to TX on the on-board max ic. Nothing on the pc, so I checked every pin with my scope, nothing but noise except for one pin that outputs steady -5v.. The prop pin however works fine!

Any ideas?

Tracy Allen

Attach your program?

Crosswinds

Sure here it comes:

But as stated before, the prop output pin works OK when listening with the scope. Its "after" the max chip that the problem seem to occur

CON


  _CLKMODE = XTAL1 + PLL16X
  _XINFREQ = 5_000_000
  clockfreq = ((_CLKMODE - XTAL1) >> 6) * _XINFREQ
  

OBJ


debug : "FullDuplexSerial"


PUB main

debug.start(7,8,0,9600)



waitcnt(clkfreq * 1 + cnt)

repeat
  debug.str(string("Hello\n"))
  waitcnt(clkfreq * 1 + cnt)

Tracy Allen

Where is the signal getting lost? Specifically, logical pin p8 on the Prop and physical pin 11 (tx1in) of the MAX3232 should both have the "Hello" and then physical pin 14 (t1out) of the MAX3232 should have it inverted at+/-5 levels.

Crosswinds

Yes, proppin have it, also the max3232 tx1in have it. But after that there is none. Just dead.. however, the t1out does have a steady negative 5v signal. But no more than that..

Peter Jakacki

Remember that RX sometimes gets labeled TX and TX labeled RX. Don't be fooled, an RX is an input and a TX is a output so TX from the Prop connects to TXin on the MAX which connects to TXout on the MAX which goes to RX on the PC.

BTW, if you are trying to measure a signal with the meter it won't show those positive transitions, the best you will get is a slightly less negative voltage when the Prop is transmitting as the meter only gives you a DC average.