diff --git a/src/descriptor.c b/src/descriptor.c
index 403b67a..617c279 100644
--- a/src/descriptor.c
+++ b/src/descriptor.c
@@ -171,6 +171,7 @@ static const dc_descriptor_t g_descriptors[] = {
 	{"Sherwood", "Amphos",              DC_FAMILY_OCEANIC_ATOM2, 0x4545},
 	{"Oceanic",  "Pro Plus 3",          DC_FAMILY_OCEANIC_ATOM2, 0x4548},
 	{"Oceanic",  "OCi",                 DC_FAMILY_OCEANIC_ATOM2, 0x454B},
+	{"Aeris",    "A300CS",              DC_FAMILY_OCEANIC_ATOM2, 0x454C},
 	/* Mares Nemo */
 	{"Mares", "Nemo",         DC_FAMILY_MARES_NEMO, 0},
 	{"Mares", "Nemo Steel",   DC_FAMILY_MARES_NEMO, 0},
diff --git a/src/oceanic_atom2.c b/src/oceanic_atom2.c
index 17e1958..733c547 100644
--- a/src/oceanic_atom2.c
+++ b/src/oceanic_atom2.c
@@ -36,6 +36,7 @@
 
 #define MAXRETRIES 2
 #define MAXDELAY   16
+#define INVALID    0xFFFFFFFF
 
 #define EXITCODE(rc) \
 ( \
@@ -49,6 +50,9 @@ typedef struct oceanic_atom2_device_t {
 	oceanic_common_device_t base;
 	serial_t *port;
 	unsigned int delay;
+	unsigned int bigpage;
+	unsigned char cache[256];
+	unsigned int cached;
 } oceanic_atom2_device_t;
 
 static dc_status_t oceanic_atom2_device_read (dc_device_t *abstract, unsigned int address, unsigned char data[], unsigned int size);
@@ -149,6 +153,10 @@ static const oceanic_common_version_t oceanic_reactpro_version[] = {
 	{"REACPRO2 \0\0 512K"},
 };
 
+static const oceanic_common_version_t aeris_a300cs_version[] = {
+	{"AER300CS \0\0 2048"},
+};
+
 static const oceanic_common_layout_t aeris_f10_layout = {
 	0x10000, /* memsize */
 	0x0000, /* cf_devinfo */
@@ -331,6 +339,19 @@ static const oceanic_common_layout_t oceanic_reactpro_layout = {
 	1 /* pt_mode_logbook */
 };
 
+static const oceanic_common_layout_t aeris_a300cs_layout = {
+	0x40000, /* memsize */
+	0x0000, /* cf_devinfo */
+	0x0040, /* cf_pointers */
+	0x0900, /* rb_logbook_begin */
+	0x1000, /* rb_logbook_end */
+	16, /* rb_logbook_entry_size */
+	0x1000, /* rb_profile_begin */
+	0x3FE00, /* rb_profile_end */
+	0, /* pt_mode_global */
+	1 /* pt_mode_logbook */
+};
+
 static dc_status_t
 oceanic_atom2_send (oceanic_atom2_device_t *device, const unsigned char command[], unsigned int csize, unsigned char ack)
 {
@@ -369,7 +390,7 @@ oceanic_atom2_send (oceanic_atom2_device_t *device, const unsigned char command[
 
 
 static dc_status_t
-oceanic_atom2_transfer (oceanic_atom2_device_t *device, const unsigned char command[], unsigned int csize, unsigned char answer[], unsigned int asize)
+oceanic_atom2_transfer (oceanic_atom2_device_t *device, const unsigned char command[], unsigned int csize, unsigned char answer[], unsigned int asize, unsigned int crc_size)
 {
 	dc_device_t *abstract = (dc_device_t *) device;
 
@@ -407,8 +428,14 @@ oceanic_atom2_transfer (oceanic_atom2_device_t *device, const unsigned char comm
 		}
 
 		// Verify the checksum of the answer.
-		unsigned char crc = answer[asize - 1];
-		unsigned char ccrc = checksum_add_uint8 (answer, asize - 1, 0x00);
+		unsigned short crc, ccrc;
+		if (crc_size == 2) {
+			crc = array_uint16_le (answer + asize - 2);
+			ccrc = checksum_add_uint16 (answer, asize - 2, 0x0000);
+		} else {
+			crc = answer[asize - 1];
+			ccrc = checksum_add_uint8 (answer, asize - 1, 0x00);
+		}
 		if (crc != ccrc) {
 			ERROR (abstract->context, "Unexpected answer checksum.");
 			return DC_STATUS_PROTOCOL;
@@ -451,6 +478,9 @@ oceanic_atom2_device_open (dc_device_t **out, dc_context_t *context, const char
 	// Set the default values.
 	device->port = NULL;
 	device->delay = 0;
+	device->bigpage = 1; // no big pages
+	device->cached = INVALID;
+	memset(device->cache, 0, sizeof(device->cache));
 
 	// Open the device.
 	int rc = serial_open (&device->port, context, name);
@@ -480,6 +510,10 @@ oceanic_atom2_device_open (dc_device_t **out, dc_context_t *context, const char
 	// Give the interface 100 ms to settle and draw power up.
 	serial_sleep (device->port, 100);
 
+	// Set the DTR/RTS lines.
+	serial_set_dtr(device->port, 1);
+	serial_set_rts(device->port, 1);
+
 	// Make sure everything is in a sane state.
 	serial_flush (device->port, SERIAL_QUEUE_BOTH);
 
@@ -526,6 +560,9 @@ oceanic_atom2_device_open (dc_device_t **out, dc_context_t *context, const char
 		device->base.layout = &oceanic_veo1_layout;
 	} else if (OCEANIC_COMMON_MATCH (device->base.version, oceanic_reactpro_version)) {
 		device->base.layout = &oceanic_reactpro_layout;
+	} else if (OCEANIC_COMMON_MATCH (device->base.version, aeris_a300cs_version)) {
+		device->base.layout = &aeris_a300cs_layout;
+		device->bigpage = 16;
 	} else {
 		device->base.layout = &oceanic_default_layout;
 	}
@@ -567,7 +604,7 @@ oceanic_atom2_device_keepalive (dc_device_t *abstract)
 
 	// Send the command to the dive computer.
 	unsigned char command[4] = {0x91, 0x05, 0xA5, 0x00};
-	dc_status_t rc = oceanic_atom2_transfer (device, command, sizeof (command), NULL, 0);
+	dc_status_t rc = oceanic_atom2_transfer (device, command, sizeof (command), NULL, 0, 0);
 	if (rc != DC_STATUS_SUCCESS)
 		return rc;
 
@@ -588,7 +625,7 @@ oceanic_atom2_device_version (dc_device_t *abstract, unsigned char data[], unsig
 
 	unsigned char answer[PAGESIZE + 1] = {0};
 	unsigned char command[2] = {0x84, 0x00};
-	dc_status_t rc = oceanic_atom2_transfer (device, command, sizeof (command), answer, sizeof (answer));
+	dc_status_t rc = oceanic_atom2_transfer (device, command, sizeof (command), answer, sizeof (answer), 1);
 	if (rc != DC_STATUS_SUCCESS)
 		return rc;
 
@@ -607,24 +644,59 @@ oceanic_atom2_device_read (dc_device_t *abstract, unsigned int address, unsigned
 		(size    % PAGESIZE != 0))
 		return DC_STATUS_INVALIDARGS;
 
+	// Pick the correct read command and number of checksum bytes.
+	unsigned char read_cmd = 0x00;
+	unsigned int crc_size = 0;
+	switch (device->bigpage) {
+	case 1:
+		read_cmd = 0xB1;
+		crc_size = 1;
+		break;
+	case 8:
+		read_cmd = 0xB4;
+		crc_size = 1;
+		break;
+	case 16:
+		read_cmd = 0xB8;
+		crc_size = 2;
+		break;
+	default:
+		return DC_STATUS_INVALIDARGS;
+	}
+
+	// Pick the best pagesize to use.
+	unsigned int pagesize = device->bigpage * PAGESIZE;
+
 	unsigned int nbytes = 0;
 	while (nbytes < size) {
-		// Read the package.
-		unsigned int number = address / PAGESIZE;
-		unsigned char answer[PAGESIZE + 1] = {0};
-		unsigned char command[4] = {0xB1,
-				(number >> 8) & 0xFF, // high
-				(number     ) & 0xFF, // low
-				0};
-		dc_status_t rc = oceanic_atom2_transfer (device, command, sizeof (command), answer, sizeof (answer));
-		if (rc != DC_STATUS_SUCCESS)
-			return rc;
+		unsigned int page = address / pagesize;
+		if (page != device->cached) {
+			// Read the package.
+			unsigned int number = page * device->bigpage; // This is always PAGESIZE, even in big page mode.
+			unsigned char answer[256 + 2] = {0};          // Maximum we support for the known commands.
+			unsigned char command[4] = {read_cmd,
+					(number >> 8) & 0xFF, // high
+					(number     ) & 0xFF, // low
+					0};
+			dc_status_t rc = oceanic_atom2_transfer (device, command, sizeof (command), answer,  pagesize + crc_size, crc_size);
+			if (rc != DC_STATUS_SUCCESS)
+				return rc;
 
-		memcpy (data, answer, PAGESIZE);
+			// Cache the page.
+			memcpy (device->cache, answer, pagesize);
+			device->cached = page;
+		}
 
-		nbytes += PAGESIZE;
-		address += PAGESIZE;
-		data += PAGESIZE;
+		unsigned int offset = address % pagesize;
+		unsigned int length = pagesize - offset;
+		if (nbytes + length > size)
+			length = size - nbytes;
+
+		memcpy (data, device->cache + offset, length);
+
+		nbytes += length;
+		address += length;
+		data += length;
 	}
 
 	return DC_STATUS_SUCCESS;
@@ -640,6 +712,9 @@ oceanic_atom2_device_write (dc_device_t *abstract, unsigned int address, const u
 		(size    % PAGESIZE != 0))
 		return DC_STATUS_INVALIDARGS;
 
+	// Invalidate the cache.
+	device->cached = INVALID;
+
 	unsigned int nbytes = 0;
 	while (nbytes < size) {
 		// Prepare to write the package.
@@ -648,7 +723,7 @@ oceanic_atom2_device_write (dc_device_t *abstract, unsigned int address, const u
 				(number >> 8) & 0xFF, // high
 				(number     ) & 0xFF, // low
 				0x00};
-		dc_status_t rc = oceanic_atom2_transfer (device, prepare, sizeof (prepare), NULL, 0);
+		dc_status_t rc = oceanic_atom2_transfer (device, prepare, sizeof (prepare), NULL, 0, 0);
 		if (rc != DC_STATUS_SUCCESS)
 			return rc;
 
@@ -656,7 +731,7 @@ oceanic_atom2_device_write (dc_device_t *abstract, unsigned int address, const u
 		unsigned char command[PAGESIZE + 2] = {0};
 		memcpy (command, data, PAGESIZE);
 		command[PAGESIZE] = checksum_add_uint8 (command, PAGESIZE, 0x00);
-		rc = oceanic_atom2_transfer (device, command, sizeof (command), NULL, 0);
+		rc = oceanic_atom2_transfer (device, command, sizeof (command), NULL, 0, 0);
 		if (rc != DC_STATUS_SUCCESS)
 			return rc;
 
diff --git a/src/oceanic_atom2_parser.c b/src/oceanic_atom2_parser.c
index 423c5a5..8dedf3f 100644
--- a/src/oceanic_atom2_parser.c
+++ b/src/oceanic_atom2_parser.c
@@ -69,6 +69,7 @@
 #define AMPHOS      0x4545
 #define PROPLUS3    0x4548
 #define OCI         0x454B
+#define A300CS      0x454C
 
 typedef struct oceanic_atom2_parser_t oceanic_atom2_parser_t;
 
@@ -218,6 +219,13 @@ oceanic_atom2_parser_get_datetime (dc_parser_t *abstract, dc_datetime_t *datetim
 			datetime->hour   = p[11];
 			datetime->minute = p[10];
 			break;
+		case A300CS:
+			datetime->year   = (p[10]) + 2000;
+			datetime->month  = (p[8]);
+			datetime->day    = (p[9]);
+			datetime->hour   = bcd2dec(p[1] & 0x1F);
+			datetime->minute = bcd2dec(p[0]);
+			break;
 		default:
 			datetime->year   = bcd2dec (((p[3] & 0xC0) >> 2) + (p[4] & 0x0F)) + 2000;
 			datetime->month  = (p[4] & 0xF0) >> 4;
@@ -325,6 +333,7 @@ oceanic_atom2_parser_get_field (dc_parser_t *abstract, dc_field_type_t type, uns
 	}
 
 	dc_gasmix_t *gasmix = (dc_gasmix_t *) value;
+	dc_salinity_t *water = (dc_salinity_t *) value;
 
 	unsigned int oxygen = 0;
 	unsigned int helium = 0;
@@ -344,20 +353,34 @@ oceanic_atom2_parser_get_field (dc_parser_t *abstract, dc_field_type_t type, uns
 				*((double *) value) = array_uint16_le (data + footer + 4) / 16.0 * FEET;
 			break;
 		case DC_FIELD_GASMIX_COUNT:
-			if (parser->model == DATAMASK || parser->model == COMPUMASK)
+			if (parser->model == DATAMASK || parser->model == COMPUMASK) {
 				*((unsigned int *) value) = 1;
-			else if (parser->model == VT4 || parser->model == VT41 || parser->model == OCI)
+			} else if (parser->model == VT4 || parser->model == VT41 ||
+				parser->model == OCI) {
 				*((unsigned int *) value) = 4;
-			else if (parser->model == TX1)
+			} else if (parser->model == TX1) {
 				*((unsigned int *) value) = 6;
-			else
+			} else if (parser->model == A300CS) {
+				if (data[0x39] & 0x04) {
+					*((unsigned int *) value) = 1;
+				} else if (data[0x39] & 0x08) {
+					*((unsigned int *) value) = 2;
+				} else if (data[0x39] & 0x10) {
+					*((unsigned int *) value) = 3;
+				} else {
+					*((unsigned int *) value) = 4;
+				}
+			} else {
 				*((unsigned int *) value) = 3;
+			}
 			break;
 		case DC_FIELD_GASMIX:
 			if (parser->model == DATAMASK || parser->model == COMPUMASK) {
 				oxygen = data[header + 3];
 			} else if (parser->model == OCI) {
 				oxygen = data[0x28 + flags];
+			} else if (parser->model == A300CS) {
+				oxygen = data[0x2A + flags];
 			} else if (parser->model == TX1) {
 				oxygen = data[0x3E + flags];
 				helium = data[0x48 + flags];
@@ -368,6 +391,18 @@ oceanic_atom2_parser_get_field (dc_parser_t *abstract, dc_field_type_t type, uns
 			gasmix->oxygen = (oxygen ? oxygen / 100.0 : 0.21);
 			gasmix->nitrogen = 1.0 - gasmix->oxygen - gasmix->helium;
 			break;
+		case DC_FIELD_SALINITY:
+			if (parser->model == A300CS) {
+				if (data[0x18] & 0x80) {
+					water->type = DC_WATER_FRESH;
+				} else {
+					water->type = DC_WATER_SALT;
+				}
+				water->density = 0.0;
+			} else {
+				return DC_STATUS_UNSUPPORTED;
+			}
+			break;
 		default:
 			return DC_STATUS_UNSUPPORTED;
 		}
@@ -404,6 +439,8 @@ oceanic_atom2_parser_samples_foreach (dc_parser_t *abstract, dc_sample_callback_
 	} else if (parser->model == F10) {
 		headersize = 3 * PAGESIZE;
 		footersize = PAGESIZE / 2;
+	} else if (parser->model == A300CS) {
+		headersize = 5 * PAGESIZE;
 	}
 
 	if (size < headersize + footersize)
@@ -415,7 +452,10 @@ oceanic_atom2_parser_samples_foreach (dc_parser_t *abstract, dc_sample_callback_
 	unsigned int time = 0;
 	unsigned int interval = 1;
 	if (parser->model != F10) {
-		switch (data[0x17] & 0x03) {
+		unsigned int idx = 0x17;
+		if (parser->model == A300CS)
+			idx = 0x1f;
+		switch (data[idx] & 0x03) {
 		case 0:
 			interval = 2;
 			break;
@@ -434,7 +474,7 @@ oceanic_atom2_parser_samples_foreach (dc_parser_t *abstract, dc_sample_callback_
 	unsigned int samplesize = PAGESIZE / 2;
 	if (parser->model == OC1A || parser->model == OC1B ||
 		parser->model == OC1C || parser->model == OCI ||
-		parser->model == TX1)
+		parser->model == TX1 || parser->model == A300CS)
 		samplesize = PAGESIZE;
 	else if (parser->model == F10)
 		samplesize = 2;
@@ -459,7 +499,10 @@ oceanic_atom2_parser_samples_foreach (dc_parser_t *abstract, dc_sample_callback_
 	unsigned int tank = 0;
 	unsigned int pressure = 0;
 	if (have_pressure) {
-		pressure = data[header + 2] + (data[header + 3] << 8);
+		unsigned int idx = 2;
+		if (parser->model == A300CS)
+			idx = 16;
+		pressure = data[header + idx] + (data[header + idx + 1] << 8);
 		if (pressure == 10000)
 			have_pressure = 0;
 	}
@@ -511,6 +554,10 @@ oceanic_atom2_parser_samples_foreach (dc_parser_t *abstract, dc_sample_callback_
 				// Tank pressure (1 psi) and number
 				tank = 0;
 				pressure = (((data[offset + 7] << 8) + data[offset + 6]) & 0x0FFF);
+			} else if (parser->model == A300CS) {
+				// Tank pressure (1 psi) and number (one based index)
+				tank = (data[offset + 1] & 0x03) - 1;
+				pressure = ((data[offset + 7] << 8) + data[offset + 6]) & 0x0FFF;
 			} else {
 				// Tank pressure (2 psi) and number (one based index)
 				tank = (data[offset + 1] & 0x03) - 1;
@@ -552,6 +599,8 @@ oceanic_atom2_parser_samples_foreach (dc_parser_t *abstract, dc_sample_callback_
 					temperature = data[offset + 1];
 				} else if (parser->model == VT4 || parser->model == VT41 || parser->model == ATOM3 || parser->model == ATOM31 || parser->model == A300AI) {
 					temperature = ((data[offset + 7] & 0xF0) >> 4) | ((data[offset + 7] & 0x0C) << 2) | ((data[offset + 5] & 0x0C) << 4);
+				} else if (parser->model == A300CS) {
+					temperature = data[offset + 11];
 				} else {
 					unsigned int sign;
 					if (parser->model == DG03 || parser->model == PROPLUS3)
@@ -584,7 +633,7 @@ oceanic_atom2_parser_samples_foreach (dc_parser_t *abstract, dc_sample_callback_
 					parser->model == ZENAIR ||parser->model == A300AI ||
 					parser->model == DG03 || parser->model == PROPLUS3)
 					pressure = (((data[offset + 0] & 0x03) << 8) + data[offset + 1]) * 5;
-				else if (parser->model == TX1)
+				else if (parser->model == TX1 || parser->model == A300CS)
 					pressure = array_uint16_le (data + offset + 4);
 				else
 					pressure -= data[offset + 1];
@@ -609,6 +658,22 @@ oceanic_atom2_parser_samples_foreach (dc_parser_t *abstract, dc_sample_callback_
 			sample.depth = depth / 16.0 * FEET;
 			if (callback) callback (DC_SAMPLE_DEPTH, sample, userdata);
 
+			// NDL / Deco
+			// bits 6..4 of byte 15 encode deco state & depth
+			// bytes 6 & 7 encode minutes of NDL / deco
+			if (parser->model == A300CS) {
+				unsigned int deco = (data[offset + 15] & 0x70) >> 4;
+				if (deco) {
+					sample.deco.type = DC_DECO_DECOSTOP;
+					sample.deco.depth = deco * 10 * FEET;
+				} else {
+					sample.deco.type = DC_DECO_NDL;
+					sample.deco.depth = 0.0;
+				}
+				sample.deco.time = array_uint16_le(data + offset + 6) & 0x03FF;
+				if (callback) callback (DC_SAMPLE_DECO, sample, userdata);
+			}
+
 			complete = 1;
 		}