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Memory use on Pixy

Pixy Software
#1

I’ve been working to implement FAST9 corner detection on the Pixy. I was able to get the stock code to compile and run using Keil and process the raw frame data within progvideo.cpp by including the FAST C code from http://www.edwardrosten.com/work/fast.html.

cam_getFrameWithoutChirp(CAM_GRAB_M1R2, 0, 0, CAM_RES2_WIDTH, CAM_RES2_HEIGHT, g_chirpUsb);
		
//cprintf("%d,%d\n", CAM_RES2_WIDTH, CAM_RES2_HEIGHT); 320 x 200
//frames have a header of length 36
uint8_t len = 36;
uint8_t *frame = len + (uint8_t *)SRAM1_LOC;

int val;
//convert to greyscale using filter
for (int i = 1 + CAM_RES2_WIDTH; i<(CAM_RES2_WIDTH*CAM_RES2_HEIGHT - CAM_RES2_WIDTH - 1);  i++){
	val = 0;
	val += 1*(frame[i + -1 - CAM_RES2_WIDTH]);
	val += 2*(frame[i +  0 - CAM_RES2_WIDTH]);
	val += 1*(frame[i +  1 - CAM_RES2_WIDTH]);
	val += 2*(frame[i + -1]);
	val += 4*(frame[i +  0]);
	val += 2*(frame[i +  1]);
	val += 1*(frame[i + -1 + CAM_RES2_WIDTH]);
	val += 2*(frame[i +  0 + CAM_RES2_WIDTH]);
	val += 1*(frame[i +  1 + CAM_RES2_WIDTH]);
	val = val / 16;
	frame[i] = (uint8_t) val;
}

int ret_num_corners;
xy ret_nonmax[MAX_CORNERS];

xy *fast9results;
fast9results = fast9_detect_nonmax(frame, CAM_RES2_WIDTH, CAM_RES2_HEIGHT, CAM_RES2_WIDTH, (uint8_t) 40, &ret_num_corners, ret_nonmax);

cprintf("corners = %d\n", ret_num_corners);
for (int i=0; i<ret_num_corners;  i++){
	frame[fast9results[i].y*CAM_RES2_WIDTH + fast9results[i].x] = (uint8_t) 255;
	//cprintf("corner[%d]: (%d,%d) \n", i, fast9results[i].x, fast9results[i].y);
	//break;
}	 	

cam_sendFrameChirp((uint8_t *)SRAM1_LOC, (uint32_t) len + (uint16_t) CAM_RES2_WIDTH * (uint16_t) CAM_RES2_HEIGHT, g_chirpUsb);

I ran into some trouble with malloc calls in the FAST9 code and ended up just allocating fixed arrays. However, I can’t track more than ~50 corners at the moment because (I think) I am storing my arrays in a working memory area… I would like to add a fixed block of memory to store the candidate corners but I haven’t figured this out yet.

In “pixyvals.h”, I see some predefined memory addresses:

// SRAM banks
#define SRAM0_LOC                0x10000000
#define SRAM0_SIZE               0x20000
#define SRAM1_LOC                0x10080000
#define SRAM1_SIZE               0x12000
#define SRAM2_LOC                0x20000000
#define SRAM2_SIZE               0x8000
#define SRAM3_LOC                0x20008000
#define SRAM3_SIZE               0x4000
#define SRAM4_LOC                0x2000c000
#define SRAM4_SIZE               0x4000

I tried to define a few more regions in between these blocks:

#define SRAM5_LOC	0x10030000
#define SRAM5_SIZE	0x20000
#define SRAM6_LOC	0x10050000
#define SRAM6_SIZE	0x20000

This doesn’t seem to work yet.

I’m curious why you left gaps in the predefined memory locations and if you think there’s a better approach that I could be following.

Thanks,

Robb

#2

Well, I found half of the answer in the 4330 spec:

// SRAM banks
// See Table 10 in 43xx User Manual
// Local SRAM 128kB
#define SRAM0_LOC                0x10000000
#define SRAM0_SIZE               0x20000
// Local SRAM 72kB
#define SRAM1_LOC                0x10080000
#define SRAM1_SIZE               0x12000
// AHB SRAM 32kB
#define SRAM2_LOC                0x20000000
#define SRAM2_SIZE               0x8000
// AHB SRAM 16kB
#define SRAM3_LOC                0x20008000
#define SRAM3_SIZE               0x4000
// AHB SRAM / ETB SRAM 16kB
#define SRAM4_LOC                0x2000c000
#define SRAM4_SIZE               0x4000

I’ll create some space in SRAM1_LOC after the frame data.

#3

Hi Robb,

Glad you found that resource. I would have pointed you to the 4330 user manual anyway. I believe your new approach will work, please let us know if you need any help.

Scott

#4

Thanks Scott - I got it working using memory blocks starting at 0x1009000

I redefined SRAM1_SIZE because it’s used to calculate buffers for sending the frame back.

I did notice this causes some error messages in blob detection, but I’m not using that code anyway.

On a related note – is there any place where I can store a previous frame safely?

Thanks,

Robb

#5

Hi Robb,

There wouldn’t be enough memory in RAM to store two frames simultaneously. You could save it to flash, however since it’s capacity is 1MB.

Scott

#6

Hi all,
Could someone tell me what the starting address is for the external flash? I see there are several locations in memory to reference external flash. many thanks!

#7

Hi Jared,

Pixy doesn’t have any external flash, only internal. The LPC4300 does support external flash, but we don’t use it. The internal flash starts at address 0x14000000.

Scott