Serial Data Garbled

masterme120

I assembled a basic Propellor circuit on a breadboard. Simple test programs work when loaded into RAM or the EEPROM, but when I try to use the FullDuplexSerial object, instead of outputting the string I give it ("Hello, world!"), it always outputs the same sequence of bytes:
"30 B7 EE DC 87 77 77 6E 03 62 CF 9F 47 EF DC 87 EE C1 FE"
Any advice would be greatly appreciated.
Here's my program for reference:

CON

  _XINFREQ = 20_000_000
  _CLKMODE = XTAL2 + PLL4X

  rxPin  = 31
  txPin  = 30
  baud   = 300

OBJ
  fdx   :       "FullDuplexSerial"                      'serial driver

PUB main

  fdx.start(31,30,0,baud)                               'start serial driver

  fdx.str(string("Hello, world!"))

Mike G

It's probably

CON

  _XINFREQ = 20_000_000
  _CLKMODE = XTAL2 + PLL4X

I use... but I have the standard 5Mhz external clock.

CON
  _clkmode = xtal1 + pll16x     
  _xinfreq = 5_000_000

Do you have a 20Mhz external clock?

Maybe.. a high speed clock? Connections? See page 68 in the propeller manual.

CON

  _XINFREQ = 20_000_000
  _CLKMODE = XTAL3 + PLL4X

Duane Degn

What serial terminal are you using?

Many of those numbers should be ASCII characters. $77 is "w".

It looks like Mike G. has found the main problem.

Welcome to the forums!

Duane

Phil Pilgrim (PhiPi)

You can't use a PLL mode with a 20 MHz crystal or a 20 MHz external clock. The VCO will just oscillate at its open-loop frequency, which will foul up your baud rate and output garbage. Keep your crystal/input frequency between 4 MHz and 10 MHz.

-Phil

Mike G

Phil, I kinda' figured it had something to do with the 20MHz clock but I could not find a spec.

You can't use a PLL mode with a 20 MHz crystal or a 20 MHz external clock

Is this information published somewhere?

Publison

Mike,

Page 26 of the Propeller Data Sheet specs xtal from 4-8 Mhz, although 10 Mhz has been used and is deemed acceptable.

14.xxx has been used, but I would think 20 Mhz is out of the realm of the PLL.

Mike G wrote: »

Phil, I kinda' figured it had something to do with the 20MHz clock but I could not find a spec.

Is this information published somewhere?