Schau die in der Bascom Hilfe mal die Funktion SHIFTIN an. Eventuell hift diese Dir. Kommt halt auf die Art des Signals an. Vielleicht kannst du in einer Schleife auf den Startzeitpunkt warten und dann "Shiftin" nutzen. Ansonsten wird bei einem schnellen Signal eine kleine Assembler-Unterroutine sicher am sinnvollsten sein.
Shifts a bit stream into a variable.
SHIFTIN pin , pclock , var , option [, bits , delay ]
Pin The port pin which serves as an input.PINB.2 for example
Pclock The port pin which generates the clock.
Var The variable that is assigned.
Option Option can be :
0 – MSB shifted in first when clock goes low
1 – MSB shifted in first when clock goes high
2 – LSB shifted in first when clock goes low
3 – LSB shifted in first when clock goes high
Adding 4 to the parameter indicates that an external clock signal is used for the clock. In this case the clock will not be generated. So using 4 will be the same a 0 (MSB shifted in first when clock goes low) but the clock must be generated by an external signal.4 – MSB shifted in first when clock goes low with ext. clock
5 – MSB shifted in first when clock goes high with ext. clock
6 – LSB shifted in first when clock goes low with ext. clock
7 – LSB shifted in first when clock goes high with ext. clock
Bits Optional number of bits to shift in. Maximum 255.
Delay Optional delay in uS. When you specify the delay, the number of bits must also be specified. When the number of bits is default you can use NULL for the BITS parameter.
If you do not specify the number of bits to shift, the number of shifts will depend on the type of the variable.
When you use a byte, 8 shifts will occur and for an integer, 16 shifts will occur. For a Long and Single 32 shifts will occur.
The SHIFTIN routine can be used to interface with all kind of chips.
The PIN is normally connected with the output of chip that will send information.
The PCLOCK pin can be used to clock the bits as a master, that is the clock pulses will be generated. Or it can sample a pin that generates these pulses.
The VARIABLE is a normal BASIC variable. And may be of any type except for BIT. The data read from the chip is stored in this variable.
The OPTIONS is a constant that specifies the direction of the bits. The chip that outputs the data may send the LS bit first or the MS bit first. It also controls on which edge of the clock signal the data must be stored.
When you add 4 to the constant you tell the compiler that the clock signal is not generated but that there is an external clock signal.
The number of bits may be specified. You may omit this info. In that case the number of bits of the element data type will be used.
The DELAY normally consists of 2 NOP instructions. When the clock is too fast you can specify a delay time(in uS).