Well, I thought I should report back on my attempt to read these sensors.
I got past my sampling problem.
It's not pretty, but it works.
In my T0 ISR, where I do mS timers, I have it sampling the inputs, using T1
to count the period of four cycles of each input.
//*********************************************************************************************
//
// Timer 0 overflow ISR
//
// 1mS timer maintainance, and sampling of the two magnetometer channels.
//
// WARNING: If either mag input stops, the app will hang!
//
ISR(TIMER0_OVF_vect)
{
TCNT0 = T0_Reload_Value; // Needed to hit 1mS ticks.
if (0 < LCD_Timer) LCD_Timer--; // Dec the pacing timer to 0
if (Raw_Samples > Raw_Data_Size) { // If the raw data buffer isn't full
TCCR1B &= ~(1<<CS10); // Stop T1
TCNT1=0; // Clear T1
// Use this when simulating.
/*
Raw_Data[0][Raw_Data_In_Index] = 0xAA;
Raw_Data[0][Raw_Data_In_Index++] = 0x55;
if ((Raw_Samples - 1) < Raw_Data_In_Index ) Raw_Data_In_Index = 0;
Raw_Data_Size++;
return;
*/
// Sync to the A channel
while (PIND & 0x04); // Wait for a low, so we know we're not seeing a
high level yet
while (!(PIND & 0x04)); // Wait for the high edge
TCCR1B |=(1<<CS10); // START the clock to T1
// T1 is now counting the pulse width.
// Since it can be as short as 5uS, we'll count four cycles.
// That can be as little as 20us (4 cycles = 80 counts)
// or as much as 92 uS (4 cycles = 368 counts)
// So we can check with the scope.
//Debug_DDR |= (1 << Debug_Pin); // Output
//Debug_Port |= (1 << Debug_Pin); // High
while (PIND & 0x04); // Wait for a low on PD2
while (!(PIND & 0x04)); // Wait for a high on PD2 One cycle has gone
while (PIND & 0x04);
while (!(PIND & 0x04)); // Now two
while (PIND & 0x04);
while (!(PIND & 0x04)); // Now three
while (PIND & 0x04);
while (!(PIND & 0x04)); // Now four
TCCR1B &= ~(1<<CS10); // Stop T1
//Debug_Port &= ~(1 << Debug_Pin); // Low
Raw_Data[0][Raw_Data_In_Index] = TCNT1; // Save the value but do NOT bump
the pointer yet
TCNT1=0; // Clear T1
// Sync to the B channel, and proceed as above
while (PIND & 0x08);
while (!(PIND & 0x08));
TCCR1B |=(1<<CS10);
while (PIND & 0x08);
while (!(PIND & 0x08));
while (PIND & 0x08);
while (!(PIND & 0x08));
while (PIND & 0x08);
while (!(PIND & 0x08));
while (PIND & 0x08);
while (!(PIND & 0x08));
TCCR1B &= ~(1<<CS10);
Raw_Data[1][Raw_Data_In_Index++] = TCNT1; // Save the value and bump the
pointer
if ((Raw_Samples - 1) < Raw_Data_In_Index ) Raw_Data_In_Index = 0;
Raw_Data_Size++;
}
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