diff --git a/main.c b/main.c
index bb723fc..616c6b3 100644
--- a/main.c
+++ b/main.c
@@ -5,7 +5,6 @@
 #include "scpi_errors.h"
 
 
-
 void cmd_aIDNq_cb(const SCPI_argval_t *args)
 {
 	printf("cb  *IDN?\n");
@@ -61,7 +60,7 @@ void cmd_STQE_cb(const SCPI_argval_t *args)
 	printf("STATUS:QUEUE:ENABLE %d\n", args[0].BOOL);
 }
 
-const SCPI_command_t scpi_cmd_lang[] = {
+const SCPI_command_t scpi_commands[] = {
 	{
 		.levels = {"*IDN?"},
 		.params = {},
@@ -114,20 +113,42 @@ const SCPI_command_t scpi_cmd_lang[] = {
 
 int main()
 {
+	char buf[256];
+
 
 //	const char *inp = "*IDN?\n";
 //	const char *inp = "FREQ 50\n";
-	const char *inp = "DISP:TEXT 'ban\\\\ana', OFF\nDISP:TEXT \"dblquot!\", 1\r\nFREQ 50\r\n";
+//	const char *inp = "DISP:TEXT 'ban\\\\ana', OFF\nDISP:TEXT \"dblquot!\", 1\r\nFREQ 50\r\n";
 
-//	const char *inp = "DATA:BLOB 13.456, #216AbcdEfghIjklMnop\nFREQ 50\r\n";
-//	const char *inp = "STAT:QUE:ENAB?;ENAB \t   1;ENAB?;:*IDN?\n";
+	const char *inp = "FOO\nDATA:BLOB 13.456, #216AbcdEfghIjklMnop\nFREQ 50\r\n";
+	//const char *inp = "STAT:QUE:ENAB?;ENAB \t   1;ENAB?;:*IDN?\n";
 
 	for (int i = 0; i < strlen(inp); i++) {
 		scpi_handle_byte(inp[i]);
 	}
 
-	char buf[250];
+
 	scpi_error_string(buf, E_EXE_DATA_QUESTIONABLE, "The data smells fishy");
 
-	printf("%s\n", buf);
+//	scpi_read_error(buf), printf("%s\n", buf);
+
+//	scpi_add_error(E_CMD_BLOCK_DATA_ERROR, NULL);
+
+//	scpi_read_error(buf), printf("%s\n", buf);
+//	scpi_read_error(buf), printf("%s\n", buf);
+//	scpi_add_error(E_CMD_DATA_TYPE_ERROR, "LOL OOPS");
+//	scpi_add_error(E_CMD_CHARACTER_DATA_TOO_LONG, "Too long data very overflow such fail");
+//	scpi_add_error(E_CMD_MACRO_PARAMETER_ERROR, "maaaacrooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo");
+//	scpi_add_error(E_CMD_EXPONENT_TOO_LARGE, NULL);
+//	scpi_add_error(E_DEV_CALIBRATION_FAILED, NULL);
+//	scpi_add_error(E_DEV_MEMORY_ERROR, NULL);
+//	scpi_read_error(buf), printf("%s\n", buf);
+//	scpi_read_error(buf), printf("%s\n", buf);
+//	scpi_read_error(buf), printf("%s\n", buf);
+//	scpi_read_error(buf), printf("%s\n", buf);
+//	scpi_add_error(E_DEV_MEMORY_ERROR, "lel");
+//	scpi_read_error(buf), printf("%s\n", buf);
+//	scpi_read_error(buf), printf("%s\n", buf);
+//	scpi_read_error(buf), printf("%s\n", buf);
+//	scpi_read_error(buf), printf("%s\n", buf);
 }
diff --git a/scpi.pro.user b/scpi.pro.user
index af18b34..f59e021 100644
--- a/scpi.pro.user
+++ b/scpi.pro.user
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE QtCreatorProject>
-<!-- Written by QtCreator 3.5.1, 2015-12-04T00:22:50. -->
+<!-- Written by QtCreator 3.5.1, 2015-12-04T17:56:40. -->
 <qtcreator>
  <data>
   <variable>EnvironmentId</variable>
diff --git a/scpi_errors.c b/scpi_errors.c
index 973a845..cfcdf7c 100644
--- a/scpi_errors.c
+++ b/scpi_errors.c
@@ -12,6 +12,7 @@ typedef struct {
 } SCPI_error_desc;
 
 static const SCPI_error_desc error_table[] = {
+	{ 0, "No error"},
 	{ -100, "Command error"},
 	{ -101, "Invalid character"},
 	{ -102, "Syntax error"},
@@ -133,13 +134,13 @@ static const SCPI_error_desc error_table[] = {
 	{ -600, "User request"},
 	{ -700, "Request control"},
 	{ -800, "Operation complete"},
-	{0}
+	{ -9999} // end mark
 };
 
 
 const char * scpi_error_message(SCPI_error_t errno)
 {
-	for (int i = 0; error_table[i].errno != 0; i++) {
+	for (int i = 0; error_table[i].errno != -9999; i++) {
 		if (error_table[i].errno == errno) {
 			return error_table[i].msg;
 		}
@@ -159,9 +160,7 @@ void scpi_error_string(char *buffer, SCPI_error_t errno, const char *extra)
 	len = offs = sprintf(buffer, "%d,\"", errno); // <code>,"
 	buffer += offs;
 
-	if (msg == NULL) {
-		msg = "Unknown error";
-	}
+	if (msg == NULL) msg = "Unknown error";
 
 	offs = sprintf(buffer, "%s", msg); // Error message
 	len += offs;
@@ -169,7 +168,7 @@ void scpi_error_string(char *buffer, SCPI_error_t errno, const char *extra)
 
 	if (extra != NULL) {
 		// extra info
-		offs = sprintf(buffer, "; "); // ;_
+		offs = sprintf(buffer, ";"); // ;
 		len += offs;
 		buffer += offs;
 
diff --git a/scpi_errors.h b/scpi_errors.h
index 1b86abe..5b83078 100644
--- a/scpi_errors.h
+++ b/scpi_errors.h
@@ -4,6 +4,7 @@
 
 // SCPI error constants
 typedef enum {
+	E_NO_ERROR = 0,
 	E_COMMAND_ERROR = -100,
 	E_CMD_INVALID_CHARACTER = -101,
 	E_CMD_SYNTAX_ERROR = -102,
diff --git a/scpi_parser.c b/scpi_parser.c
index a4fd813..f11e50c 100644
--- a/scpi_parser.c
+++ b/scpi_parser.c
@@ -1,11 +1,38 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include <string.h>
-#include "scpi_parser.h"
 
 #include <stdio.h>
 #include <stdlib.h>
 
+#include "scpi_parser.h"
+#include "scpi_errors.h"
+
+// Config
+#define ERR_QUEUE_LEN 4
+#define MAX_ERROR_LEN 255
+#define MAX_CHARBUF_LEN 255
+
+
+// Char matching
+#define INRANGE(c, a, b) ((c) >= (a) && (c) <= (b))
+#define IS_WHITESPACE(c) (INRANGE((c), 0, 9) || INRANGE((c), 11, 32))
+
+#define IS_LCASE_CHAR(c) INRANGE((c), 'a', 'z')
+#define IS_UCASE_CHAR(c) INRANGE((c), 'A', 'Z')
+#define IS_NUMBER_CHAR(c) INRANGE((c), '0', '9')
+#define IS_MULTIPLIER_CHAR(c) ((c) == 'k' || (c) == 'M' || (c) == 'G' || (c) == 'm' || (c) == 'u' || (c) == 'n' || (c) == 'p')
+
+#define IS_IDENT_CHAR(c) (IS_LCASE_CHAR((c)) || IS_UCASE_CHAR((c)) || IS_NUMBER_CHAR((c)) || (c) == '_' || (c) == '*' || (c) == '?')
+#define IS_INT_CHAR(c) (IS_NUMBER_CHAR((c)) || (c) == '-' || (c) == '+' || IS_MULTIPLIER_CHAR((c)))
+#define IS_FLOAT_CHAR(c) (IS_NUMBER_CHAR((c)) || (c) == '.' || (c) == 'e' || (c) == 'E' || (c) == '+' || (c) == '-' || IS_MULTIPLIER_CHAR((c)))
+
+#define CHAR_TO_LOWER(ucase) ((ucase) + 32)
+#define CHAR_TO_UPPER(lcase) ((lcase) - 32)
+
+
+
+/** Parser internal state enum */
 typedef enum {
 	PARS_COMMAND = 0,
 	// collect generic arg, terminated with comma or newline. Leading and trailing whitespace ignored.
@@ -19,17 +46,19 @@ typedef enum {
 	PARS_DISCARD_LINE, // used after detecting error - drop all chars until \n
 } parser_state_t;
 
-#define MAX_CHARBUF_LEN 256
 
-/** parser internal state struct */
+
+/** Parser internal state struct */
 static struct {
-	char err_queue[ERR_QUEUE_LEN][MAX_ERROR_LEN];
-	uint8_t err_queue_i;
+	char err_queue[ERR_QUEUE_LEN][MAX_ERROR_LEN + 1];
+	int8_t err_queue_r;
+	int8_t err_queue_w;
+	int8_t err_queue_used; // signed for backtracking
 
 	parser_state_t state; // current parser internal state
 
 	// string buffer, chars collected here until recognized
-	char charbuf[MAX_CHARBUF_LEN];
+	char charbuf[MAX_CHARBUF_LEN + 1];
 	uint16_t charbuf_i;
 
 	int32_t blob_cnt; // preamble counter, if 0, was just #, must read count. Used also for blob body.
@@ -39,146 +68,125 @@ static struct {
 	bool string_escape; // last char was backslash, next quote is literal
 
 	// recognized complete command level strings (FUNCtion) - exact copy from command struct
-	char cur_levels[MAX_LEVEL_COUNT][MAX_CMD_LEN];
+	char cur_levels[SCPI_MAX_LEVEL_COUNT][SCPI_MAX_CMD_LEN];
 	uint8_t cur_level_i; // next free level slot index
 
 	bool cmdbuf_kept; // set to 1 after semicolon - cur_levels is kept (removed last part)
 
 	const SCPI_command_t * matched_cmd; // command is put here after recognition, used as reference for args
 
-	SCPI_argval_t args[MAX_PARAM_COUNT];
+	SCPI_argval_t args[SCPI_MAX_PARAM_COUNT];
 	uint8_t arg_i; // next free argument slot index
 
 } pst = {0}; // initialized by all zeros
 
 
+
+// ---------------- PRIVATE PROTOTYPES ------------------
+
+// Command parsing
 static void pars_cmd_colon(void); // colon starting a command sub-segment
 static void pars_cmd_space(void); // space ending a command
 static void pars_cmd_newline(void); // LF
 static void pars_cmd_semicolon(void); // semicolon right after a command
-static bool pars_match_cmd(bool partial);
+
+// Command properties (find length of array)
+static uint8_t cmd_param_count(const SCPI_command_t *cmd);
+static uint8_t cmd_level_count(const SCPI_command_t *cmd);
+
+static bool match_cmd(bool partial);
+static bool match_any_cmd_from_array(const SCPI_command_t arr[], bool partial);
+static bool match_cmd_do(const SCPI_command_t *cmd, bool partial);
+static void run_command_callback(void);
+
+// Argument parsing
 static void pars_arg_char(char c);
 static void pars_arg_comma(void);
 static void pars_arg_newline(void);
 static void pars_arg_semicolon(void);
 static void pars_blob_preamble_char(uint8_t c);
+static void arg_convert_value(void);
 
-static uint8_t cmd_param_count(const SCPI_command_t *cmd);
-static uint8_t cmd_level_count(const SCPI_command_t *cmd);
-
-static bool try_match_cmd(const SCPI_command_t *cmd, bool partial);
 static void charbuf_terminate(void);
 static void charbuf_append(char c);
-static void pars_run_callback(void);
-static void arg_convert_value(void);
-
-// char matching
-#define INRANGE(c, a, b) ((c) >= (a) && (c) <= (b))
-#define IS_WHITESPACE(c) (INRANGE((c), 0, 9) || INRANGE((c), 11, 32))
-
-#define IS_LCASE_CHAR(c) INRANGE((c), 'a', 'z')
-#define IS_UCASE_CHAR(c) INRANGE((c), 'A', 'Z')
-#define IS_NUMBER_CHAR(c) INRANGE((c), '0', '9')
-#define IS_MULTIPLIER_CHAR(c) ((c) == 'k' || (c) == 'M' || (c) == 'G' || (c) == 'm' || (c) == 'u' || (c) == 'n' || (c) == 'p')
 
-#define IS_IDENT_CHAR(c) (IS_LCASE_CHAR((c)) || IS_UCASE_CHAR((c)) || IS_NUMBER_CHAR((c)) || (c) == '_' || (c) == '*' || (c) == '?')
-#define IS_INT_CHAR(c) (IS_NUMBER_CHAR((c)) || (c) == '-' || (c) == '+' || IS_MULTIPLIER_CHAR((c)))
-#define IS_FLOAT_CHAR(c) (IS_NUMBER_CHAR((c)) || (c) == '.' || (c) == 'e' || (c) == 'E' || (c) == '+' || (c) == '-' || IS_MULTIPLIER_CHAR((c)))
+// Reset
+static void pars_reset_cmd(void);
+static void pars_reset_cmd_keeplevel(void);
 
-#define CHAR_TO_LOWER(ucase) ((ucase) + 32)
-#define CHAR_TO_UPPER(lcase) ((lcase) - 32)
 
 
+// ---------------- BUILTIN SCPI COMMANDS ------------------
 
-/** Reset parser state. */
-static void pars_reset_cmd(void)
+static void builtin_cb_FOO(const SCPI_argval_t *args)
 {
-	pst.state = PARS_COMMAND;
-	pst.charbuf_i = 0;
-	pst.cur_level_i = 0;
-	pst.cmdbuf_kept = false;
-	pst.matched_cmd = NULL;
-	pst.arg_i = 0;
-	pst.string_escape = false;
+	printf("Builtin FOO\n");
 }
 
 
-/** Reset parser state, keep level (semicolon) */
-static void pars_reset_cmd_keeplevel(void)
-{
-	pst.state = PARS_COMMAND;
-	pst.charbuf_i = 0;
+const SCPI_command_t scpi_commands_builtin[] = {
+	{
+		.levels = {"FOO"},
+		.params = {},
+		.callback = builtin_cb_FOO
+	},
+	{0} // end marker
+};
 
-	// rewind to last colon
-	if (pst.cur_level_i > 0) {
-		pst.cur_level_i--; // keep prev levels
-	}
 
-	pst.cmdbuf_kept = true;
-	pst.matched_cmd = NULL;
-	pst.arg_i = 0;
-	pst.string_escape = false;
-}
 
+// ------------------- ERROR QUEUE ---------------------
 
-static uint8_t cmd_param_count(const SCPI_command_t *cmd)
+void scpi_add_error(SCPI_error_t errno, const char *extra)
 {
-	for (uint8_t i = 0; i < MAX_PARAM_COUNT; i++) {
-		if (cmd->params[i] == SCPI_DT_NONE) {
-			return i;
+	bool added = true;
+	if (pst.err_queue_used >= ERR_QUEUE_LEN) {
+		errno = E_DEV_QUEUE_OVERFLOW;
+		extra = NULL;
+		added = false; // replaced only
+
+		// backtrack
+		pst.err_queue_w--;
+		pst.err_queue_used--;
+		if (pst.err_queue_w < 0) {
+			pst.err_queue_w = ERR_QUEUE_LEN - 1;
 		}
 	}
 
-	return MAX_PARAM_COUNT;
-}
-
+	scpi_error_string(pst.err_queue[pst.err_queue_w], errno, extra);
 
-static uint8_t cmd_level_count(const SCPI_command_t *cmd)
-{
-	for (uint8_t i = 0; i < MAX_LEVEL_COUNT; i++) {
-		if (cmd->levels[i][0] == 0) {
-			return i;
-		}
+	pst.err_queue_w++;
+	pst.err_queue_used++;
+	if (pst.err_queue_w >= ERR_QUEUE_LEN) {
+		pst.err_queue_w = 0;
 	}
-
-	return MAX_LEVEL_COUNT;
 }
 
 
-/** Add a byte to charbuf, error on overflow */
-static void charbuf_append(char c)
+void scpi_read_error(char *buf)
 {
-	if (pst.charbuf_i >= MAX_CHARBUF_LEN) {
-		printf("ERROR string buffer overflow.\n");//TODO error
-		pst.state = PARS_DISCARD_LINE;
+	if (pst.err_queue_used == 0) {
+		scpi_error_string(buf, E_NO_ERROR, NULL);
+		return;
 	}
 
-	pst.charbuf[pst.charbuf_i++] = c;
-}
-
+	strcpy(buf, pst.err_queue[pst.err_queue_r++]);
+	pst.err_queue_used--;
 
-/** Terminate charbuf and rewind the pointer to start */
-static void charbuf_terminate(void)
-{
-	pst.charbuf[pst.charbuf_i] = '\0';
-	pst.charbuf_i = 0;
+	if (pst.err_queue_r >= ERR_QUEUE_LEN) {
+		pst.err_queue_r = 0;
+	}
 }
 
 
-/** Run the matched command's callback with the arguments */
-static void pars_run_callback(void)
+uint8_t scpi_error_count(void)
 {
-	if (pst.matched_cmd != NULL) {
-		pst.matched_cmd->callback(pst.args); // run
-	}
+	return pst.err_queue_used;
 }
 
 
-void scpi_discard_blob(void)
-{
-	pst.state = PARS_ARG_BLOB_DISCARD;
-}
 
+// ----------------- INPUT PARSING ----------------
 
 void scpi_handle_byte(const uint8_t b)
 {
@@ -192,7 +200,7 @@ void scpi_handle_byte(const uint8_t b)
 			if (IS_IDENT_CHAR(c)) {
 				// valid command char
 
-				if (pst.charbuf_i < MAX_CMD_LEN) {
+				if (pst.charbuf_i < SCPI_MAX_CMD_LEN) {
 					charbuf_append(c);
 				} else {
 					printf("ERROR command part too long.\n");//TODO error
@@ -239,8 +247,8 @@ void scpi_handle_byte(const uint8_t b)
 			if (IS_WHITESPACE(c)) break;
 
 			if (c == '\n') {
-				if(pst.state != PARS_TRAILING_WHITE_NOCB) {
-					pars_run_callback();
+				if (pst.state != PARS_TRAILING_WHITE_NOCB) {
+					run_command_callback();
 				}
 
 				pars_reset_cmd();
@@ -334,6 +342,105 @@ void scpi_handle_byte(const uint8_t b)
 }
 
 
+
+// ------------------- RESET INTERNAL STATE ------------------
+
+
+// public //
+/** Discard the rest of the currently processed blob */
+void scpi_discard_blob(void)
+{
+	if (pst.state == PARS_ARG_BLOB_BODY) {
+		pst.state = PARS_ARG_BLOB_DISCARD;
+	}
+}
+
+
+/** Reset parser state. */
+static void pars_reset_cmd(void)
+{
+	pst.state = PARS_COMMAND;
+	pst.charbuf_i = 0;
+	pst.cur_level_i = 0;
+	pst.cmdbuf_kept = false;
+	pst.matched_cmd = NULL;
+	pst.arg_i = 0;
+	pst.string_escape = false;
+}
+
+
+/** Reset parser state, keep level (semicolon) */
+static void pars_reset_cmd_keeplevel(void)
+{
+	pst.state = PARS_COMMAND;
+	pst.charbuf_i = 0;
+
+	// rewind to last colon
+	if (pst.cur_level_i > 0) {
+		pst.cur_level_i--; // keep prev levels
+	}
+
+	pst.cmdbuf_kept = true;
+	pst.matched_cmd = NULL;
+	pst.arg_i = 0;
+	pst.string_escape = false;
+}
+
+
+// ------------------- COMMAND HELPERS -------------------
+
+/** Get param count from command struct */
+static uint8_t cmd_param_count(const SCPI_command_t *cmd)
+{
+	for (uint8_t i = 0; i < SCPI_MAX_PARAM_COUNT; i++) {
+		if (cmd->params[i] == SCPI_DT_NONE) {
+			return i;
+		}
+	}
+
+	return SCPI_MAX_PARAM_COUNT;
+}
+
+
+/** Get level count from command struct */
+static uint8_t cmd_level_count(const SCPI_command_t *cmd)
+{
+	for (uint8_t i = 0; i < SCPI_MAX_LEVEL_COUNT; i++) {
+		if (cmd->levels[i][0] == 0) {
+			return i;
+		}
+	}
+
+	return SCPI_MAX_LEVEL_COUNT;
+}
+
+
+
+// ----------------- CHAR BUFFER HELPERS -------------------
+
+/** Add a byte to charbuf, error on overflow */
+static void charbuf_append(char c)
+{
+	if (pst.charbuf_i >= MAX_CHARBUF_LEN) {
+		printf("ERROR string buffer overflow.\n");//TODO error
+		pst.state = PARS_DISCARD_LINE;
+	}
+
+	pst.charbuf[pst.charbuf_i++] = c;
+}
+
+
+/** Terminate charbuf and rewind the pointer to start */
+static void charbuf_terminate(void)
+{
+	pst.charbuf[pst.charbuf_i] = '\0';
+	pst.charbuf_i = 0;
+}
+
+
+
+// ----------------- PARSING COMMANDS ---------------
+
 /** Colon received when collecting command parts */
 static void pars_cmd_colon(void)
 {
@@ -351,7 +458,7 @@ static void pars_cmd_colon(void)
 
 	} else {
 		// internal colon - partial match
-		if (pars_match_cmd(true)) {
+		if (match_cmd(true)) {
 			// ok
 		} else {
 			printf("ERROR no such command: %s\n", pst.charbuf);//TODO error
@@ -361,6 +468,7 @@ static void pars_cmd_colon(void)
 }
 
 
+/** Semiolon received when collecting command parts */
 static void pars_cmd_semicolon(void)
 {
 	if (pst.cur_level_i == 0 && pst.charbuf_i == 0) {
@@ -370,10 +478,10 @@ static void pars_cmd_semicolon(void)
 		return;
 	}
 
-	if (pars_match_cmd(false)) {
+	if (match_cmd(false)) {
 		if (cmd_param_count(pst.matched_cmd) == 0) {
 			// no param command - OK
-			pars_run_callback();
+			run_command_callback();
 			pars_reset_cmd_keeplevel(); // keep level - that's what semicolon does
 		} else {
 			printf("ERROR command missing arguments.\n");//TODO error
@@ -396,10 +504,10 @@ static void pars_cmd_newline(void)
 	}
 
 	// complete match
-	if (pars_match_cmd(false)) {
+	if (match_cmd(false)) {
 		if (cmd_param_count(pst.matched_cmd) == 0) {
 			// no param command - OK
-			pars_run_callback();
+			run_command_callback();
 			pars_reset_cmd();
 		} else {
 			printf("ERROR command missing arguments.\n");//TODO error
@@ -420,7 +528,7 @@ static void pars_cmd_space(void)
 		return;
 	}
 
-	if (pars_match_cmd(false)) {
+	if (match_cmd(false)) {
 		if (cmd_param_count(pst.matched_cmd) == 0) {
 			// no commands
 			pst.state = PARS_TRAILING_WHITE;
@@ -500,7 +608,7 @@ static bool level_str_matches(const char *test, const char *pattern)
 
 
 
-static bool pars_match_cmd(bool partial)
+static bool match_cmd(bool partial)
 {
 	charbuf_terminate(); // zero-end and rewind index
 
@@ -508,17 +616,30 @@ static bool pars_match_cmd(bool partial)
 	char *dest = pst.cur_levels[pst.cur_level_i++];
 	strcpy(dest, pst.charbuf);
 
+
+	// First try builtin commands
+	if (match_any_cmd_from_array(scpi_commands_builtin, partial)) {
+		return true;
+	}
+
+	// User commands
+	return match_any_cmd_from_array(scpi_commands, partial);
+}
+
+
+static bool match_any_cmd_from_array(const SCPI_command_t arr[], bool partial)
+{
 	for (uint16_t i = 0; i < 0xFFFF; i++) {
 
-		const SCPI_command_t *cmd = &scpi_cmd_lang[i];
+		const SCPI_command_t *cmd = &arr[i];
 		if (cmd->levels[0][0] == 0) break; // end marker
 
-		if (cmd_level_count(cmd) > MAX_LEVEL_COUNT) {
+		if (cmd_level_count(cmd) > SCPI_MAX_LEVEL_COUNT) {
 			// FAIL, too deep. Bad config
 			continue;
 		}
 
-		if (try_match_cmd(cmd, partial)) {
+		if (match_cmd_do(cmd, partial)) {
 			if (partial) {
 				// match found, OK
 				return true;
@@ -535,7 +656,7 @@ static bool pars_match_cmd(bool partial)
 
 
 /** Try to match current state to a given command */
-static bool try_match_cmd(const SCPI_command_t *cmd, bool partial)
+static bool match_cmd_do(const SCPI_command_t *cmd, bool partial)
 {
 	const uint8_t level_cnt = cmd_level_count(cmd);
 	if (pst.cur_level_i > level_cnt) return false; // command too short
@@ -562,6 +683,18 @@ static bool try_match_cmd(const SCPI_command_t *cmd, bool partial)
 }
 
 
+/** Run the matched command's callback with the arguments */
+static void run_command_callback(void)
+{
+	if (pst.matched_cmd != NULL) {
+		pst.matched_cmd->callback(pst.args); // run
+	}
+}
+
+
+
+// ---------------------- PARSING ARGS --------------------------
+
 /** Non-whitespace and non-comma char received in arg. */
 static void pars_arg_char(char c)
 {
@@ -645,7 +778,7 @@ static void pars_arg_newline(void)
 	}
 
 	arg_convert_value();
-	pars_run_callback();
+	run_command_callback();
 
 	pars_reset_cmd(); // start a new command
 }
@@ -661,7 +794,7 @@ static void pars_arg_semicolon(void)
 	}
 
 	arg_convert_value();
-	pars_run_callback();
+	run_command_callback();
 
 	pars_reset_cmd_keeplevel(); // start a new command, keep level
 }
@@ -709,7 +842,7 @@ static void arg_convert_value(void)
 			break;
 
 		case SCPI_DT_STRING:
-			if (strlen(pst.charbuf) > MAX_STRING_LEN) {
+			if (strlen(pst.charbuf) > SCPI_MAX_STRING_LEN) {
 				printf("ERROR string too long.\n");//TODO error
 				pst.state = PARS_DISCARD_LINE;
 			} else {
@@ -728,12 +861,13 @@ static void arg_convert_value(void)
 	pst.arg_i++;
 }
 
+
 static void pars_blob_preamble_char(uint8_t c)
 {
 	if (pst.blob_cnt == 0) {
 		if (!INRANGE(c, '1', '9')) {
 			printf("ERROR expected ASCII 1-9 after #\n");//TODO error
-			pst.state = PARS_DISCARD_LINE;
+			pst.state = PARS_DISCARD_LINE;// not enough to remove the blob containing \n
 			return;
 		}
 
@@ -759,7 +893,7 @@ static void pars_blob_preamble_char(uint8_t c)
 			sscanf(pst.charbuf, "%d", &pst.blob_len);
 
 			pst.args[pst.arg_i].BLOB_LEN = pst.blob_len;
-			pars_run_callback();
+			run_command_callback();
 
 			// Call handler, enter special blob mode
 			pst.state = PARS_ARG_BLOB_BODY;
diff --git a/scpi_parser.h b/scpi_parser.h
index e822a4c..f55cd45 100644
--- a/scpi_parser.h
+++ b/scpi_parser.h
@@ -1,14 +1,13 @@
 #pragma once
+#include "scpi_errors.h"
+
 #include <stdint.h>
 #include <stdbool.h>
 
-#define MAX_CMD_LEN 12
-#define MAX_STRING_LEN 12
-#define MAX_LEVEL_COUNT 4
-#define MAX_PARAM_COUNT 4
-
-#define ERR_QUEUE_LEN 4
-#define MAX_ERROR_LEN 100
+#define SCPI_MAX_CMD_LEN 12
+#define SCPI_MAX_STRING_LEN 12
+#define SCPI_MAX_LEVEL_COUNT 4
+#define SCPI_MAX_PARAM_COUNT 4
 
 /** Argument data types */
 typedef enum {
@@ -26,25 +25,27 @@ typedef union {
 	float FLOAT;
 	int32_t INT;
 	bool BOOL;
-	char STRING[MAX_STRING_LEN+1]; // terminator
+	char STRING[SCPI_MAX_STRING_LEN + 1]; // terminator
 	uint32_t BLOB_LEN;
 } SCPI_argval_t;
 
 
+// ------ CONFIGURATION --------
+
 /**
  * SCPI command preset
  * NOTE: command array is terminated by {0} - zero in levels[0][0]
  */
 typedef struct {
 	// levels MUST BE FIRST!
-	const char levels[MAX_LEVEL_COUNT][MAX_CMD_LEN]; // up to 4 parts
+	const char levels[SCPI_MAX_LEVEL_COUNT][SCPI_MAX_CMD_LEN]; // up to 4 parts
 
 	// called when the command is completed. BLOB arg must be last in the argument list,
 	// and only the first part is collected.
 	void (*callback)(const SCPI_argval_t *args);
 
 	// Param types - optional (defaults to zeros)
-	const SCPI_datatype_t params[MAX_PARAM_COUNT]; // parameter types (0 for unused)
+	const SCPI_datatype_t params[SCPI_MAX_PARAM_COUNT]; // parameter types (0 for unused)
 
 	// --- OPTIONAL (only for blob) ---
 
@@ -54,8 +55,9 @@ typedef struct {
 	void (*blob_callback)(const uint8_t *bytes);
 } SCPI_command_t;
 
-// Zero terminated command struct array
-extern const SCPI_command_t scpi_cmd_lang[];
+
+// Zero terminated command struct array - must be defined.
+extern const SCPI_command_t scpi_commands[];
 
 
 // --------------- functions --------------------
@@ -66,3 +68,19 @@ extern const SCPI_command_t scpi_cmd_lang[];
  */
 void scpi_handle_byte(const uint8_t b);
 
+/** Add error to the error queue */
+void scpi_add_error(SCPI_error_t errno, const char *extra);
+
+/** Get number of errors in the error queue */
+uint8_t scpi_error_count(void);
+
+/**
+ * Read and remove one entry from the error queue.
+ * Returns 0,"No error" if the queue is empty.
+ *
+ * The entry is copied to the provided buffer, which must be 256 chars long.
+ */
+void scpi_read_error(char *buf);
+
+/** Discard the rest of the currently processed blob */
+void scpi_discard_blob(void);