blob: 96fdc1d6e25bd7dc8cfc0b6a6a1e7e9135cd45cb (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
|
#ifndef MYRADIO_PHY_RECEIVER_H_
#define MYRADIO_PHY_RECEIVER_H_
/* Lowlevel receiver definitions.
* These functions do poke with the actual RX hardware.
*/
#include "util.h"
#include <avr/io.h>
/* Our receiver is based on the AnalogToDigital-converter 0.
* We basically get a binary signal from the radio. The radio
* hardware did already demodulate the HF signal and filter
* out any HF.
* Our tunable is the threshold value for the logical HIGH.
* The ADC is in freerunning mode and continuously scans the
* input pin. The current status can be fetched by calling the
* receiver_get_current_signal() function.
* Note that the current signal is delayed by the ADC delay, which
* is defined by the ADC prescaler. However, as our prescaler is 64
* we run the ADC at a frequency of 250kHz (16Mhz crystal). That means
* our delay is as low as 4 microseconds.
*/
//FIXME tune this to the correct value for our radio
#define RECEIVER_THRESHOLD 50 /* in ADC LSBs */
static inline bool receiver_get_current_signal(void)
{
return (ADC > RECEIVER_THRESHOLD);
}
static inline void receiver_initialize(void)
{
/* Multiplexer = ADC0; Reference = AVcc */
ADMUX = (1 << REFS0);
/* Enable ADC; Prescaler = 64 */
ADCSRA = (1 << ADEN) | (1 << ADPS1) | (1 << ADPS2);
/* Poke the ADC once to initialize it */
ADCSRA |= (1 << ADSC);
while (ADCSRA & (1 << ADSC))
mb();
/* Now enable free-running mode. */
ADCSRA |= (1 << ADSC) | (1 << ADFR);
}
#endif /* MYRADIO_PHY_RECEIVER_H_ */
|
