[Tinyos-devel] Bug in Msp430TimerControl.nc interface

[Eric Decker]

Kevin and I implemented a hardware assisted s/w uart using Timer A2 and in
the process of debugging I found the following problem:
In tos/chips/msp430/timer/Msp430TimerControl.nc setControlAsCapture is
defined as:

    async command void setControlAsCapture(bool low_to_high);

note the bool low_to_high.

But in the actual implementation in
tos/chips/msp430/timer/Msp430TimerCapComP.nc

  async command void Control.setControlAsCapture( uint8_t cm )
  {
     TxCCTLx = captureControl( cm );
  }

and captureControl looks like:

  uint16_t captureControl(uint8_t l_cm)
  {
=>  cc_t x = {
      cm : l_cm & 0x03,    // capture on rising edge
      ccis : 0,  // capture/compare input select
      clld : 0,  // TBCL1 loads on write to TBCCR1
      cap : 1,   // compare mode
      scs : 1,   // synchronous capture mode
      ccie : 0,  // capture compare interrupt enable
    };
    return CC2int(x);
  }


So the interface definition lies.  The compiler doesn't catch the definition
mismatch because bool is a uint8_t.

I would propose:

Index: timer/Msp430TimerCapComP.nc
===================================================================
RCS file:
/cvsroot/tinyos/tinyos-2.x/tos/chips/msp430/timer/Msp430TimerCapComP.nc,v
retrieving revision 1.3
diff -u -r1.3 Msp430TimerCapComP.nc
--- timer/Msp430TimerCapComP.nc 16 Feb 2008 20:03:51 -0000      1.3
+++ timer/Msp430TimerCapComP.nc 20 May 2008 03:53:11 -0000
@@ -58,10 +58,10 @@
     return CC2int(x);
   }

-  uint16_t captureControl(uint8_t l_cm)
+  uint16_t captureControl(bool low_to_high)
   {
     cc_t x = {
-      cm : l_cm & 0x03,    // capture on rising edge
+      cm : (low_to_high ? 1 : 2), // 0b01 gives rising, 0b10 gives falling
       ccis : 0,  // capture/compare input select
       clld : 0,  // TBCL1 loads on write to TBCCR1
       cap : 1,   // compare mode


who supports msp430 timers these days?

-- 
Eric B. Decker
Senior (over 50 :-) Researcher
Autonomous Systems Lab
Jack Baskin School of Engineering
UCSC
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