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Re: [Discuss-gnuradio] setting fields in the USB packet
From: |
Eric Blossom |
Subject: |
Re: [Discuss-gnuradio] setting fields in the USB packet |
Date: |
Fri, 6 Apr 2007 11:23:06 -0700 |
User-agent: |
Mutt/1.5.9i |
On Fri, Apr 06, 2007 at 12:17:40PM -0400, George Nychis wrote:
> actually some of this is changing to pmt related stuff, now that I'm
> reading more in to the pmt class. I'm going to check in some high level
> stuff in my branch tonight probably that you can look over instead.
George, I don't think any pmt stuff should enter into these functions.
This shouldn't take that long to implement. Here's 75% of the answer:
#include <usrp_bytesex.h>
static const int USB_PKT_SIZE = 512; // bytes
class usrp_inband_usb_packet {
//
// keep raw packet in USRP-endian order
//
uint32_t d_word0;
uint32_t d_timestamp;
unsigned char d_payload[USB_PKT_SIZE-2*sizeof(uint32_t)];
public:
enum flags {
FL_OVERRUN = 0x80000000,
FL_UNDERRUN = 0x40000000,
FL_DROPPED = 0x20000000,
FL_END_OF_BURST = 0x10000000,
FL_START_OF_BURST = 0x08000000,
FL_ALL_FLAGS = 0xf8000000
};
...
static const int CHAN_MASK = 0x1f;
static const int CHAN_SHIFT = 16;
...
public:
void set_timestamp(uint32_t timestamp){
d_timestamp = host_to_usrp_u32(timestamp);
}
uint32_t timestamp() const {
return usrp_to_host_u32(d_timestamp);
}
void set_header(int flags, int chan, int tag, int payload_len){
uint32_t word0 = ((flags & FL_ALL_FLAGS)
| ((chan & CHAN_MASK) << CHAN_SHIFT)
| ((tag & TAG_MASK) << TAG_SHIFT)
| ((payload_len & PAYLOAD_LEN_MASK) <<
PAYLOAD_LEN_SHIFT));
d_word0 = host_to_usrp_u32(word0);
}
int flags() const {
return usrp_to_host_u32(d_word0) & FL_ALL_FLAGS;
}
int rssi() const {
...
}
int chan() const {
uint32_t word0 = usrp_to_host_u32(d_word0);
return (word0 >> CHAN_SHIFT) & CHAN_MASK;
}
int tag() const {
...
}
int payload_len() const {
...
}
...
//! return pointer to byte 0 of payload area
unsigned char *payload(){ return d_payload; }
};
> - George
>
>
> George Nychis wrote:
> >Heyo,
> >
> >Eric, I think you started to mention something about this last night.
> >But do we want a separate method for setting each field in the USB
> >packet? There are several fields that we won't ever need to set on our
> >end, only need to read. For instance, the dropped packets field.
> >
> >So heres what i'm thinking:
> >
> >// Create the payload
> >// 'packet_ptr' is a pointer to a USB packet in memory
> >// 'samples' is a vector of unsigned char
> >//
> >// the payload can be inferred from the samples and inserted in to the
> >packet
> >//
> >// the method should also pad the payload
> >
> >usb_set_payload(packet_ptr, samples)
> >
> >
> >// Set the timestamp
> >//
> >// 'packet_ptr' is a pointer to a USB packet in memory
> >// 'timestamp' is a 32 bit int
> >
> >usb_set_timestamp(packet_ptr, timestamp)
> >
> >
> >// Set the channel
> >//
> >// 'packet_ptr' is a pointer to a USB packet in memory
> >// 'channel' is an integer
> >//
> >// Should this also error check on the channel number? (5-bit limit)
> >
> >usb_set_channel(packet_ptr, channel)
> >
> >
> >// Set the start of burst flag
> >//
> >// 'packet_ptr' is a pointer to a USB packet in memory
> >//
> >// This just needs to flip a bit
> >
> >usb_set_start_of_burst(packet_ptr)
> >
> >
> >// Set the end of burst flag
> >//
> >// 'packet_ptr' is a pointer to a USB packet in memory
> >//
> >// This just needs to flip a bit
> >
> >usb_set_end_of_burst(packet_ptr)
> >
> >
> >Discussion:
> >-----------
> >
> >Do we need methods to unset burst flags? I don't see a need for them.
> >
> >Should we have a method to zero out the packet? Or are we just going to
> >just use low level memory clearing methods?
> >
> >- George