Propeller with Parallax GPS Receiver Module

Michael Rankin · 2006-10-10 02:33

I'm new to the spin language and was seeking some·help with this setup/code.
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I have the propeller·demo board·and the Parallax GPS Receiver Module. The 4 pins on the GPS module are GND, VCC, SIO, and RAW. Currently, I have the GND pin going to VSS on the propeller demo board, VCC going to 5V on the demo board, and SIO going to I/O pin number 0 on the board.
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What I am having trouble with is sending this header value "!GPS" plus a hex value (0x00) to the SIO pin (i/o pin 0)·and then receiving the·2 bytes back on i/o pin 0.
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I am using the FullDuplexSerial v1.1 for the serial communication. Here is the code I have so far.
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Any help is appreciated. Thanks.
·
Michael

CON
  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000
OBJ
  text : "vga_text"
  serial : "FullDuplexSerial1_1"
  
VAR
  Byte  RX_value[noparse][[/noparse]2]
  Byte  Index
  
PUB start
  text.start(16)
  
  dira[noparse][[/noparse]01]~~
  serial.start(1,1,0,4800)
  serial.tx($21)
  serial.tx($47)
  serial.tx($50)
  serial.tx($53)
  serial.tx($00)
  
  dira[noparse][[/noparse]01]~ 
  Index := 0
  repeat 3
    RX_value[noparse][[/noparse]Index++] := serial.rx
  
  Index := 0
  repeat 3
    text.hex(RX_value[noparse][[/noparse]Index++],8)
    text.out($0D)

El Paisa · 2006-10-10 02:51

Hi,

This may help you.

· serial.str(@msg1)·····
· serial.tx($00)
· waitcnt(900_000+cnt)

DAT
· msg1··· byte··· "!GPS",0

I use this format to communicate with a uMMC card writer/reader.

Hope this help.

El Paisa · 2006-10-10 02:57

Hi again,

The program I use to communicate with a uMMC card writer/reader is :

''*****************************
'' uMMC_1.spin
''*****************************

CON

· _clkmode····· = xtal1 + pll16x
· _xinfreq····· = 5_000_000
· RX_PIN······· = 2
· TX_PIN······· = 3
· MODE········· = %0000································ ' see FullDuplexSerial.spin for description
· BAUD········· = 9600
·····
VAR

······· long··· k

OBJ

······· term··· : "tv_terminal"
······· serial· : "fullduplexserial"

PUB start | i

· serial.start(RX_PIN, TX_PIN, MODE, BAUD)·········· ' initialize serial object
· waitcnt(4_000_000+cnt)

··· term.start(12)
··· term.str(@title)·
··· waitcnt(40_000_000+cnt)

'

[noparse][[/noparse]Main starts here]

· term.str(@msg1)
· term.out($09)····
· serial.str(@msg1)·····
· serial.tx(13)
· waitcnt(900_000+cnt)
· repeat until k==">"·········
··· k:=serial.rx
··· term.out(k)

DAT
· title·· byte··· "First uMMC Read/Write",13,13,0
· msg1··· byte··· "V",0

Michael Rankin · 2006-10-10 02:57

I modified my code to implement your change and I get the same output:

0x21 which is !
0x47 which is G
It looks like I am just getting back the command I am sending. I don't know if the GPS module is returning that or the code is reading it from memory

Post Edited (Michael Rankin) : 10/10/2006 1:47:18 PM GMT

ALIBE · 2006-10-10 18:37

Michael,
try this following code. Note, I have removed the use of fullduplex and am using 2 code snippets courtesy of Mike Green. It works like a charm for me in my AC4790 work I am doing w my ALIBE project.
hope this works for you

Const
  #1, Pin_GPS
Var 
  byte buffer[noparse][[/noparse]256] 

Pub Main |s  
  DirA[noparse][[/noparse]Pin_GPS]~~ 
  repeat 
    buffer[noparse][[/noparse]0] := "!"
    buffer[noparse][[/noparse]1] := "G"    
    buffer[noparse][[/noparse]2] := "P"    
    buffer[noparse][[/noparse]3] := "S"
    buffer[noparse][[/noparse]4] := $0
    txData 
    rxData 
    
PUB rxData | c, x 
  x := 0 
  repeat until (c := SerialIn(Pin_GPS, 4800,1,8) ) == 0 
    buffer[noparse][[/noparse]x++] := c 
  buffer[noparse][[/noparse]x] := 0 

PUB txData|x 
  x := 0 
  repeat until (buffer[noparse][[/noparse]x] == 0) 
   SerialOut(Pin_GPS, buffer[noparse][[/noparse]x++], 4800, 1, 8) 

 
'//
'// Code courtesy of Mike Green
'//
PUB serialIn(pin, Baud, mode, bits) | bitTime, time 
  {{ Accepts asynchronous byte value on defined pin, at Baud, in mode for #bits 
     Mode: 0 = Inverted - Normally low Constant: Inv 
     1 = Non-Inverted - Normally high Constant: NInv }} 
   
   dira[noparse][[/noparse]pin]~ ' Set up input pin as an input 
   bitTime := clkfreq / Baud ' Calculate bit time for Baud 
   waitpeq(mode << pin, |< pin, 0) ' Wait for idle (should be idle) 
   waitpne(mode << pin, |< pin, 0) ' Now wait for start of start bit 
   time := cnt ' Wait until middle of start bit 
   waitcnt(time += bitTime >> 1) 
   repeat bits ' Sample input at the middle of 
     waitcnt(time += bitTime) ' each data bit time for #bits 
     result := ((ina[noparse][[/noparse]pin] ^ (1 - mode)) << bits | result) >> 1 


'//
'// Code courtesy of Mike Green
'//
PUB serialOut(pin, char, Baud, mode, bits ) | bitTime, time 
  {{ Send asynchronous character (byte) on defined pin, at Baud, in Mode for #bits 
     Mode: 0 = Inverted - Normally low Constant: Inv 
     1 = Non-Inverted - Normally high Constant: NInv }} 
  outa[noparse][[/noparse]pin] := mode ' Set up output pin with the proper 
  dira[noparse][[/noparse]pin]~~ ' idle state and as an output 
  bitTime := clkfreq / Baud ' Calculate bit time for Baud 
  char := ((1 << bits | char) << 1) ^ (mode == 0) ' Add start/stop bits & invert if needed 
  time := cnt 
  repeat bits + 2 ' Send each bit based on baud rate 
   outa[noparse][[/noparse]Pin] := char 
   char >>= 1 
   waitcnt(time += bitTime) 
  waitcnt(time += bitTime * (bits + 2)) ' Allow a character time for pacing

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ALIBE - Artificial LIfe BEing. In search of building autonoumous land robot

http://ALIBE.crosscity.com/
http://fstop.crosscity.com/
http://icar.crosscity.com/
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Propeller with Parallax GPS Receiver Module

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