Receive UDP frames and slice them for the teensy

pru.h

@@ -7,6 +7,7 @@
 
 #include <stdio.h>
 #include <inttypes.h>
+#include "util.h"
 
 
 /** Mapping of the PRU memory spaces.
@@ -45,13 +46,6 @@ pru_close(
 );
 
 
-#define die(fmt, ...) \
-	do { \
-		fprintf(stderr, "%s:%d: " fmt, \
-			__func__, __LINE__, ## __VA_ARGS__); \
-		exit(EXIT_FAILURE); \
-	} while (0)
-
 
 /** Configure a GPIO pin.
  *

teensy-udp-rx.c

@@ -0,0 +1,125 @@
+/** \file
+ *  UDP image packet receiver.
+ *
+ * Based on the HackRockCity LED Display code:
+ * https://github.com/agwn/pyramidTransmitter/blob/master/LEDDisplay.pde
+ *
+ * Designed to clock data out to USB teensy3 serial devices, which require
+ * bitslicing into the raw form for the OctoWS2811 firmware.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <string.h>
+#include "util.h"
+
+
+/** Prepare one Teensy3 worth of image data.
+ * Each Teensy handles 8 rows of data and needs the bits sliced into
+ * each 8 rows.
+ */
+void
+bitslice(
+	uint8_t * const out,
+	const uint8_t * in,
+	const unsigned width,
+	const unsigned y_offset
+)
+{
+	// Reorder from RGB in the input to GRB in the output
+	static const uint8_t channel_map[] = { 1, 0, 2 };
+
+	// Skip to the starting row that we're processing
+	in += y_offset * width;
+
+	for(unsigned x=0 ; x < width ; x++)
+	{
+		for (unsigned channel = 0 ; channel < 3 ; channel++)
+		{
+			const uint8_t mapped_channel
+				= channel_map[channel];
+
+			for (unsigned bit_num = 0 ; bit_num < 8 ; bit_num++)
+			{
+				uint8_t b = 0;
+				const uint8_t mask = 1 << (7 - bit_num);
+
+				for(unsigned y = 0 ; y < 8 ; y++)
+				{
+					const uint8_t v
+						= in[x + y*width + channel];
+					if (v & mask)
+						b |= 1 << y;
+				}
+
+				out[x + 3*mapped_channel + bit_num] = b;
+			}
+		}
+	}
+}
+
+
+int
+main(
+	int argc,
+	char ** argv
+)
+{
+	int port = 9999;
+	unsigned width = 10;
+	unsigned height = 8;
+
+	const int sock = socket(AF_INET, SOCK_DGRAM, 0);
+	struct sockaddr_in addr = {
+		.sin_family = AF_INET,
+		.sin_port = htons(port),
+		.sin_addr.s_addr = INADDR_ANY,
+	};
+
+	if (sock < 0)
+		die("socket failed: %s\n", strerror(errno));
+	if (bind(sock, (const struct sockaddr*) &addr, sizeof(addr)) < 0)
+		die("bind port %d failed: %s\n", port, strerror(errno));
+
+	const size_t slice_size = width * height * 3 + 3;
+	uint8_t * const slice = calloc(1, slice_size);
+
+	uint8_t buf[65536];
+
+	while (1)
+	{
+		const ssize_t rc = recv(sock, buf, sizeof(buf), 0);
+		if (rc < 0)
+			die("recv failed: %s\n", strerror(errno));
+
+		if (buf[0] == '2')
+		{
+			// image type
+			printf("image type: %.*s\n",
+				(int) rc - 1,
+				&buf[1]
+			);
+			continue;
+		}
+
+		// Header for the frame to the teensy indicating that it
+		// is to be drawn immediately.
+		slice[0] = '%';
+		slice[1] = 0;
+		slice[2] = 0;
+
+		// Translate the image from packed RGB into sliced 24-bit
+		// for each teensy.
+		for (unsigned y_offset = 0 ; y_offset < height ; y_offset += 8)
+		{
+			bitslice(slice+3, buf+1, width, y_offset);
+			write(1, slice, slice_size);
+		}
+	}
+
+	return 0;
+}

util.h

@@ -0,0 +1,21 @@
+/** \file
+ * Utility functions.
+ */
+#ifndef _util_h_
+#define _util_h_
+
+#include <stdio.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <unistd.h>
+
+#define die(fmt, ...) \
+	do { \
+		fprintf(stderr, "%s:%d: " fmt, \
+			__func__, __LINE__, ## __VA_ARGS__); \
+		exit(EXIT_FAILURE); \
+	} while (0)
+
+
+#endif