diff --git a/F1:F103/BISS_C_encoders/bissC.c b/F1:F103/BISS_C_encoders/bissC.c
new file mode 100644
index 0000000..78f03f1
--- /dev/null
+++ b/F1:F103/BISS_C_encoders/bissC.c
@@ -0,0 +1,146 @@
+/*
+ * This file is part of the encoders project.
+ * Copyright 2025 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "bissC.h"
+#include "usb_dev.h"
+#ifdef EBUG
+#include "strfunc.h"
+#endif
+#include "flash.h"
+
+#define MAX_BITSTREAM_UINTS 4  // 4 * 32 = 128 bits capacity
+// min/max zeros before preambule
+#define MINZEROS    4
+#define MAXZEROS    40
+
+static uint32_t bitstream[MAX_BITSTREAM_UINTS] = {0};
+
+// Get bit at position n from uint32_t array (MSB-first packing)
+static inline uint8_t get_bit(uint8_t n) {
+    return (bitstream[n >> 5] >> (31 - (n & 0x1F))) & 1;
+}
+
+// Convert bytes to packed uint32_t bitstream (MSB-first)
+static void bytes_to_bitstream(const uint8_t *bytes, uint32_t num_bytes, uint32_t *num_bits) {
+    *num_bits = 0;
+    uint32_t current = 0;
+    uint32_t pos = 0;
+
+    for(uint32_t i = 0; i < num_bytes; i++){
+        for(int8_t j = 7; j >= 0; j--){ // MSB first
+            current = (current << 1) | ((bytes[i] >> j) & 1);
+            if (++(*num_bits) % 32 == 0){
+                bitstream[pos++] = current;
+                current = 0;
+            }
+        }
+    }
+    /* Store remaining bits if any
+    if(*num_bits % 32 != 0){
+        current <<= (32 - (*num_bits % 32));
+        bitstream[pos] = current;
+    }*/
+}
+
+// Compute CRC-6 using polynomial x^6 + x + 1
+static uint8_t compute_crc(uint8_t start_bit, uint8_t num_bits) {
+    uint8_t crc = 0x00;
+    for(uint32_t i = 0; i < num_bits; i++) {
+        uint8_t bit = get_bit(start_bit + i);
+        uint8_t msb = (crc >> 5) ^ bit;
+        crc = ((crc << 1) & 0x3F);
+        if (msb) crc ^= 0x03;
+    }
+    DBG("Compute CRC:");
+    DBGs(uhex2str(crc));
+    return crc;
+}
+
+BiSS_Frame parse_biss_frame(const uint8_t *bytes, uint32_t num_bytes){
+    BiSS_Frame frame = {0};
+    uint32_t num_bits = 0;
+    register uint8_t enclen = the_conf.encbits;
+
+    bytes_to_bitstream(bytes, num_bytes, &num_bits);
+
+    // Preamble detection state machine
+    enum {SEARCH_START, SEARCH_ZERO, COUNT_ZEROS} state = SEARCH_START;
+    uint32_t zero_count = 0;
+    uint32_t data_start = 0;
+    int found = 0;
+
+    for(uint32_t i = 0; i < num_bits && !found; i++){
+        uint8_t curbit = get_bit(i);
+        switch(state){
+        case SEARCH_START:
+            if(curbit){
+                state = SEARCH_ZERO;
+            }
+            break;
+        case SEARCH_ZERO:
+            if(!curbit){
+                state = COUNT_ZEROS;
+                zero_count = 1;
+            }
+            break;
+        case COUNT_ZEROS:
+            if(!curbit){
+                zero_count++;
+            }else{
+                if(zero_count >= MINZEROS && zero_count <= MAXZEROS){
+                    if((i + 1) < num_bits && !get_bit(i + 1)){
+                        data_start = i + 2;
+                        found = 1;
+                    }
+                }
+                state = SEARCH_START;
+            }
+            break;
+        }
+    }
+
+    // Validate frame structure
+    if(!found || (data_start + enclen+8) > num_bits){
+        frame.frame_valid = 0;
+        return frame;
+    }
+    DBG("Data start:");
+    DBGs(u2str(data_start));
+    // Extract 26-bit data
+    for(int i = 0; i < enclen; i++){
+        frame.data <<= 1;
+        frame.data |= get_bit(data_start + i);
+    }
+
+    // Extract 2-bit flags (INVERTED!)
+    frame.error = !get_bit(data_start + enclen);
+    frame.warning = !get_bit(data_start + enclen + 1);
+
+    // Extract and validate CRC
+    uint8_t received_crc = 0;
+    for(uint32_t i = 0; i < 6; i++){
+        received_crc <<= 1;
+        // CRC transmitted MSB and inverted! Include position data and EW bits
+        if(!get_bit(data_start + enclen + 2 + i)) received_crc |= 1;
+    }
+    DBG("received CRC:");
+    DBGs(uhex2str(received_crc));
+    frame.crc_valid = (compute_crc(data_start, enclen + 2) == received_crc);
+    frame.frame_valid = 1;
+    return frame;
+}
diff --git a/F1:F103/BISS_C_encoders/bissC.h b/F1:F103/BISS_C_encoders/bissC.h
new file mode 100644
index 0000000..b7816eb
--- /dev/null
+++ b/F1:F103/BISS_C_encoders/bissC.h
@@ -0,0 +1,31 @@
+/*
+ * This file is part of the encoders project.
+ * Copyright 2025 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+typedef struct {
+    uint32_t data;              // 26/32/36-bit data
+    uint8_t error : 1;          // error flag (0 - error: bad value or high temperature)
+    uint8_t warning : 1;        // warning flag (0 - warning: need to be cleaned)
+    uint8_t crc_valid : 1;      // CRC validation result
+    uint8_t frame_valid : 1;    // Overall frame validity
+} BiSS_Frame;
+
+BiSS_Frame parse_biss_frame(const uint8_t *bytes, uint32_t num_bytes);
diff --git a/F1:F103/BISS_C_encoders/encoders.bin b/F1:F103/BISS_C_encoders/encoders.bin
index 93ac16a..660b8d1 100755
Binary files a/F1:F103/BISS_C_encoders/encoders.bin and b/F1:F103/BISS_C_encoders/encoders.bin differ
diff --git a/F1:F103/BISS_C_encoders/encoders.creator.user b/F1:F103/BISS_C_encoders/encoders.creator.user
index 7ce7566..1de570b 100644
--- a/F1:F103/BISS_C_encoders/encoders.creator.user
+++ b/F1:F103/BISS_C_encoders/encoders.creator.user
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE QtCreatorProject>
-<!-- Written by QtCreator 15.0.1, 2025-03-26T17:57:31. -->
+<!-- Written by QtCreator 15.0.1, 2025-04-02T14:36:26. -->
 <qtcreator>
  <data>
   <variable>EnvironmentId</variable>
diff --git a/F1:F103/BISS_C_encoders/encoders.files b/F1:F103/BISS_C_encoders/encoders.files
index 29882c6..ee57130 100644
--- a/F1:F103/BISS_C_encoders/encoders.files
+++ b/F1:F103/BISS_C_encoders/encoders.files
@@ -1,3 +1,5 @@
+bissC.c
+bissC.h
 flash.c
 flash.h
 hardware.c
diff --git a/F1:F103/BISS_C_encoders/flash.c b/F1:F103/BISS_C_encoders/flash.c
index 5a64626..5b23653 100644
--- a/F1:F103/BISS_C_encoders/flash.c
+++ b/F1:F103/BISS_C_encoders/flash.c
@@ -27,13 +27,14 @@ extern const uint32_t __varsstart, _BLOCKSIZE;
 static const uint32_t FLASH_blocksize = (uint32_t)&_BLOCKSIZE;
 static uint32_t maxCnum = 1024 / sizeof(user_conf); // can't use blocksize here
 
-#define USERCONF_INITIALIZER  {         \
-     .userconf_sz = sizeof(user_conf)   \
-    }
-
 static int write2flash(const void*, const void*, uint32_t);
 const user_conf *Flash_Data = (const user_conf *)(&__varsstart);
-user_conf the_conf = USERCONF_INITIALIZER;
+user_conf the_conf = {
+    .userconf_sz = sizeof(user_conf),
+    .flags.CPOL = 1,
+    .flags.BR = 4,
+    .encbits = 26
+};
 
 int currentconfidx = -1; // index of current configuration
 
diff --git a/F1:F103/BISS_C_encoders/flash.h b/F1:F103/BISS_C_encoders/flash.h
index fb7c002..ae80899 100644
--- a/F1:F103/BISS_C_encoders/flash.h
+++ b/F1:F103/BISS_C_encoders/flash.h
@@ -27,6 +27,12 @@
 // maximal size (in letters) of iInterface for settings
 #define MAX_IINTERFACE_SZ   (16)
 
+typedef struct{
+    uint8_t CPOL : 1;
+    uint8_t CPHA : 1;
+    uint8_t BR   : 3;
+} flags_t;
+
 /*
  * struct to save user configurations
  */
@@ -34,6 +40,8 @@ typedef struct __attribute__((packed, aligned(4))){
     uint16_t userconf_sz;       // "magick number"
     uint16_t iInterface[bTotNumEndpoints][MAX_IINTERFACE_SZ]; // hryunikod!
     uint8_t iIlengths[bTotNumEndpoints];
+    flags_t flags;      // flags: CPOL, CPHA etc
+    uint8_t encbits;    // encoder bits: 26 or 32
 } user_conf;
 
 extern user_conf the_conf;
diff --git a/F1:F103/BISS_C_encoders/main.c b/F1:F103/BISS_C_encoders/main.c
index 8f9b5bf..3d0633d 100644
--- a/F1:F103/BISS_C_encoders/main.c
+++ b/F1:F103/BISS_C_encoders/main.c
@@ -16,25 +16,97 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "bissC.h"
 #include "flash.h"
 #include "hardware.h"
 #include "proto.h"
 #include "spi.h"
 #include "strfunc.h"
-#include "usart.h"
+//#include "usart.h"
 #include "usb_dev.h"
 
 volatile uint32_t Tms = 0;
+static char inbuff[RBINSZ];
 
 /* Called when systick fires */
 void sys_tick_handler(void){
     ++Tms;
 }
 
-int main(){
-    char inbuff[RBINSZ];
-    uint32_t lastT = 0, lastS = 0;
+// usefull data bytes: start/0+26bit+8bit=36
+#define USEFULL_DATA_BYTES (5)
+
+static void printResult(BiSS_Frame *result){
+    if(result->frame_valid){
+        CMDWR("Data: "); CMDWRn(uhex2str(result->data));
+        if(result->error) CMDWRn("ERROR flag set");
+        if(result->warning) CMDWRn("WARNING flag set");
+        CMDWR("CRC is "); if(!result->crc_valid) CMDWR("NOT ");
+        CMDWRn("valid");
+    }else CMDWRn("Invalid frame");
+}
+
+static void proc_enc(uint8_t idx){
     uint8_t encbuf[ENCODER_BUFSZ];
+    static uint32_t lastMSG[2], gotgood[2], gotwrong[2];
+    int iface = idx ? I_Y : I_X;
+    char ifacechr = idx ? 'Y' : 'X';
+    if(CDCready[iface]){
+        int l = USB_receivestr(iface, inbuff, RBINSZ);
+        if(CDCready[I_CMD]){
+            if(l){
+                CMDWR("Enc"); USB_putbyte(I_CMD, ifacechr);
+                CMDWR(": ");
+            }
+            if(l < 0) CMDWRn("ERROR! USB buffer overflow or string was too long");
+            else if(l){
+                CMDWR("got string: '");
+                CMDWR(inbuff);
+                CMDWR("'\n");
+            }
+        }
+    }
+    if(!spi_read_enc(idx, encbuf)) return;
+    BiSS_Frame result = parse_biss_frame(encbuf, ENCODER_BUFSZ);
+    char *str = result.crc_valid ? u2str(result.data) : NULL;
+    uint8_t testflag = (idx) ? user_pars.testy : user_pars.testx;
+    if(CDCready[I_CMD]){
+        if(testflag){
+            if(Tms - lastMSG[idx] > 9999){
+                USB_putbyte(I_CMD, ifacechr);
+                CMDWR(" 10sec stat: good=");
+                CMDWR(u2str(gotgood[idx]));
+                CMDWR(", bad=");
+                CMDWR(u2str(gotwrong[idx]));
+                CMDn();
+                gotgood[idx] = 0;
+                gotwrong[idx] = 0;
+                lastMSG[idx] = Tms;
+            }else{
+                if(str) ++gotgood[idx];
+                else ++gotwrong[idx];
+            }
+        }else{
+            printResult(&result);
+            CMDWR("ENC"); USB_putbyte(I_CMD, ifacechr);
+            USB_putbyte(I_CMD, '=');
+            hexdump(I_CMD, encbuf, ENCODER_BUFSZ);
+            CMDWR(" (");
+            if(str) CMDWR(str);
+            else CMDWR("wrong");
+            CMDWR(")\n");
+        }
+    }
+    if(CDCready[iface] && str && !result.error){
+        USB_sendstr(iface, str);
+        USB_putbyte(iface, '\n');
+    }
+    if(result.error) spi_setup(1+idx); // reinit SPI in case of error
+    if(testflag) spi_start_enc(idx);
+}
+
+int main(){
+    uint32_t lastT = 0;//, lastS = 0;
     StartHSE();
     flashstorage_init();
     hw_setup();
@@ -68,50 +140,18 @@ int main(){
 #endif
 */
         if(CDCready[I_CMD]){
-            if(Tms - lastS > 9999){
+            /*if(Tms - lastS > 9999){
                 USB_sendstr(I_CMD, "Tms=");
                 USB_sendstr(I_CMD, u2str(Tms));
-                newline(I_CMD);
+                CMDn();
                 lastS = Tms;
-            }
+            }*/
             int l = USB_receivestr(I_CMD, inbuff, RBINSZ);
             if(l < 0) CMDWRn("ERROR: CMD USB buffer overflow or string was too long");
             else if(l) parse_cmd(inbuff);
         }
-        int showval = spi_read_enc(0, encbuf);
-        if(CDCready[I_CMD] && showval){
-            CMDWR("ENCX=");
-            hexdump(I_CMD, encbuf, ENCODER_BUFSZ);
-            newline(I_CMD);
-        }
-        if(CDCready[I_X]){
-            int l = USB_receivestr(I_X, inbuff, RBINSZ);
-            if(l < 0) CMDWRn("ERROR: encX USB buffer overflow or string was too long");
-            else if(l){
-                CMDWR("EncX got: '");
-                CMDWR(inbuff);
-                CMDWR("'\n");
-            }
-            if(showval) // send encoder data
-                hexdump(I_X, encbuf, ENCODER_BUFSZ);
-        }
-        showval = spi_read_enc(1, encbuf);
-        if(CDCready[I_CMD] && showval){
-            CMDWR("ENCY=");
-            hexdump(I_CMD, encbuf, ENCODER_BUFSZ);
-            newline(I_CMD);
-        }
-        if(CDCready[I_Y]){
-            int l = USB_receivestr(I_Y, inbuff, RBINSZ);
-            if(l < 0) CMDWRn("ERROR: encY USB buffer overflow or string was too long");
-            else if(l){
-                CMDWR("EncY got: '");
-                CMDWR(inbuff);
-                CMDWR("'\n");
-            }
-            if(showval) // send encoder data
-                hexdump(I_Y, encbuf, ENCODER_BUFSZ);
-        }
+        proc_enc(0);
+        proc_enc(1);
     }
     return 0;
 }
diff --git a/F1:F103/BISS_C_encoders/proto.c b/F1:F103/BISS_C_encoders/proto.c
index f02b134..8001187 100644
--- a/F1:F103/BISS_C_encoders/proto.c
+++ b/F1:F103/BISS_C_encoders/proto.c
@@ -25,6 +25,9 @@
 #include "usb_dev.h"
 #include "version.inc"
 
+// user runtime parameters
+parameters_t user_pars = {0};
+
 // error codes
 typedef enum {
     ERR_OK,         // no errors
@@ -63,6 +66,12 @@ typedef enum{
     C_spistat,
     C_spiinit,
     C_spideinit,
+    C_cpol,
+    C_cpha,
+    C_br,
+    C_encbits,
+    C_testX,
+    C_testY,
     C_AMOUNT
 } cmd_e;
 
@@ -81,7 +90,6 @@ static const funcdescr_t commands[C_AMOUNT];
                             CMDWR(i2str(ival)); CMDn(); return ERR_SILENCE; }while(0)
 
 static errcode_e help(cmd_e idx, char* par);
-static errcode_e dumpconf(cmd_e idx, char *par);
 
 static errcode_e dummy(cmd_e idx, char *par){
     static int32_t val = -111;
@@ -215,6 +223,110 @@ static errcode_e spideinit(_U_ cmd_e idx, _U_ char *par){
     return ERR_SILENCE;
 }
 
+static errcode_e setflags(cmd_e idx, char *par){
+    if(par){
+        if(*par < '0' || *par > '9') return ERR_BADPAR;
+        uint8_t val = *par - '0';
+        switch(idx){
+        case C_cpha:
+            if(val > 1) return ERR_BADPAR;
+            the_conf.flags.CPHA = val;
+            break;
+        case C_cpol:
+            if(val > 1) return ERR_BADPAR;
+            the_conf.flags.CPOL = val;
+            break;
+        case C_br:
+            if(val == 0 || val > 7) return ERR_BADPAR;
+            the_conf.flags.BR = val;
+            break;
+        default:
+            return ERR_BADCMD;
+        }
+    }
+    uint8_t val = 0;
+    switch(idx){
+    case C_cpha:
+        val = the_conf.flags.CPHA;
+        break;
+    case C_cpol:
+        val = the_conf.flags.CPOL;
+        break;
+    case C_br:
+        val = the_conf.flags.BR;
+        break;
+    default:
+        return ERR_BADCMD;
+    }
+    CMDWR(commands[idx].cmd);
+    USB_putbyte(I_CMD, '=');
+    USB_putbyte(I_CMD, '0' + val);
+    CMDn();
+    return ERR_SILENCE;
+}
+
+static errcode_e encbits(cmd_e idx, char *par){
+    if(par){
+        uint32_t N;
+        if(par == getnum(par, &N)) return ERR_BADPAR;
+        if(N < 26 || N > 32) return ERR_BADPAR; // don't support less than 26 of more than 32
+        the_conf.encbits = N;
+    }
+    CMDWR(commands[idx].cmd);
+    USB_putbyte(I_CMD, '=');
+    CMDWR(u2str(the_conf.encbits));
+    CMDn();
+    return ERR_SILENCE;
+}
+
+static errcode_e setboolpar(cmd_e idx, char *par){
+    uint8_t val;
+    if(par){
+        if(*par != '0' && *par != '1') return ERR_BADPAR;
+        val = *par - '0';
+        switch(idx){
+            case C_testX:
+                user_pars.testx = val;
+            break;
+            case C_testY:
+                user_pars.testy = val;
+            break;
+            default:
+                return ERR_BADCMD;
+        }
+    }
+    switch(idx){
+        case C_testX:
+            val = user_pars.testx;
+            if(val) spi_start_enc(0);
+        break;
+        case C_testY:
+            val = user_pars.testy;
+            if(val) spi_start_enc(1);
+        break;
+        default:
+            return ERR_BADCMD;
+    }
+    CMDWR(commands[idx].cmd);
+    USB_putbyte(I_CMD, '=');
+    USB_putbyte(I_CMD, '0' + val);
+    CMDn();
+    return ERR_SILENCE;
+}
+
+static errcode_e dumpconf(cmd_e _U_ idx, char _U_ *par){
+    CMDWR("userconf_sz="); CMDWR(u2str(the_conf.userconf_sz));
+    CMDWR("\ncurrentconfidx="); CMDWR(i2str(currentconfidx));
+    CMDn();
+    for(int i = 0; i < bTotNumEndpoints; ++i)
+        setiface(C_setiface1 + i, NULL);
+    setflags(C_br, NULL);
+    setflags(C_cpha, NULL);
+    setflags(C_cpol, NULL);
+    encbits(C_encbits, NULL);
+    return ERR_SILENCE;
+}
+
 // text commands
 static const funcdescr_t commands[C_AMOUNT] = {
     [C_dummy] = {"dummy", dummy},
@@ -235,17 +347,14 @@ static const funcdescr_t commands[C_AMOUNT] = {
     [C_spistat] = {"spistat", spistat},
     [C_spiinit] = {"spiinit", spiinit},
     [C_spideinit] = {"spideinit", spideinit},
+    [C_cpol] = {"CPOL", setflags},
+    [C_cpha] = {"CPHA", setflags},
+    [C_br] = {"BR", setflags},
+    [C_encbits] = {"encbits", encbits},
+    [C_testX] = {"testx", setboolpar},
+    [C_testY] = {"testy", setboolpar},
 };
 
-static errcode_e dumpconf(cmd_e _U_ idx, char _U_ *par){
-    CMDWR("userconf_sz="); CMDWR(u2str(the_conf.userconf_sz));
-    CMDWR("\ncurrentconfidx="); CMDWR(i2str(currentconfidx));
-    CMDn();
-    for(int i = 0; i < bTotNumEndpoints; ++i)
-        setiface(C_setiface1 + i, NULL);
-    return ERR_SILENCE;
-}
-
 typedef struct{
     int idx;            // command index (if < 0 - just display `help` as grouping header)
     const char *help;   // help message
@@ -271,9 +380,15 @@ static const help_t helpmessages[] = {
     {C_spiinit, "init SPI"},
     {C_spistat, "get status of both SPI interfaces"},
     {-1, "Debug"},
+    {C_br, "change SPI BR register (1 - 18MHz ... 7 - 281kHz)"},
+    {C_cpha, "change CPHA value (0/1)"},
+    {C_cpol, "change CPOL value (0/1)"},
+    {C_encbits, "set encoder data bits amount"},
+    {C_fin, "reinit flash"},
     {C_sendX, "send text string to X encoder's terminal"},
     {C_sendY, "send text string to Y encoder's terminal"},
-    {C_fin, "reinit flash"},
+    {C_testX, "test X-axis throughput"},
+    {C_testY, "test Y-axis throughput"},
     {-1, NULL},
 };
 
diff --git a/F1:F103/BISS_C_encoders/proto.h b/F1:F103/BISS_C_encoders/proto.h
index 1a1ebfe..e1a0aee 100644
--- a/F1:F103/BISS_C_encoders/proto.h
+++ b/F1:F103/BISS_C_encoders/proto.h
@@ -18,4 +18,13 @@
 
 #pragma once
 
+#include <stdint.h>
+
+typedef struct{
+    uint8_t testx : 1;
+    uint8_t testy : 1;
+} parameters_t;
+
+extern parameters_t user_pars;
+
 void parse_cmd(char *cmd);
diff --git a/F1:F103/BISS_C_encoders/ringbuffer.h b/F1:F103/BISS_C_encoders/ringbuffer.h
index ed2cf95..5643b5a 100644
--- a/F1:F103/BISS_C_encoders/ringbuffer.h
+++ b/F1:F103/BISS_C_encoders/ringbuffer.h
@@ -25,12 +25,14 @@
 #include <stm32f3.h>
 #endif
 
+#include <stdatomic.h>
+
 typedef struct{
     uint8_t *data;      // data buffer
     const int length;   // its length
     int head;           // head index
     int tail;           // tail index
-    volatile int busy; // == TRUE if buffer is busy now
+    volatile atomic_int busy; // == TRUE if buffer is busy now
 } ringbuffer;
 
 int RB_read(ringbuffer *b, uint8_t *s, int len);
diff --git a/F1:F103/BISS_C_encoders/spi.c b/F1:F103/BISS_C_encoders/spi.c
index 9430a21..06bfb0f 100644
--- a/F1:F103/BISS_C_encoders/spi.c
+++ b/F1:F103/BISS_C_encoders/spi.c
@@ -17,9 +17,10 @@
  */
 
 #include <stm32f1.h>
-
-#include "spi.h"
 #include <string.h> // memcpy
+
+#include "flash.h"
+#include "spi.h"
 #include "usb_dev.h"
 #ifdef EBUG
 #include "strfunc.h"
@@ -31,7 +32,7 @@
 spiStatus spi_status[AMOUNT_OF_SPI+1] = {0, SPI_NOTREADY, SPI_NOTREADY};
 static volatile SPI_TypeDef* const SPIs[AMOUNT_OF_SPI+1] = {NULL, SPI1, SPI2};
 static volatile DMA_Channel_TypeDef * const DMAs[AMOUNT_OF_SPI+1] = {NULL, DMA1_Channel2, DMA1_Channel4};
-#define WAITX(x)  do{volatile uint32_t  wctr = 0; while((x) && (++wctr < 360000)) IWDG->KR = IWDG_REFRESH; if(wctr==360000){ DBG("timeout"); return 0;}}while(0)
+#define WAITX(x)  do{volatile uint32_t  wctr = 0; while((x) && (++wctr < 3600)) IWDG->KR = IWDG_REFRESH; if(wctr==3600){ DBG("timeout"); return 0;}}while(0)
 
 static uint8_t encoderbuf[AMOUNT_OF_SPI][ENCODER_BUFSZ] = {0};
 static uint8_t freshdata[AMOUNT_OF_SPI] = {0};
@@ -46,13 +47,14 @@ void spi_setup(uint8_t idx){
     SPI->CR2 = 0;
     RCC->AHBENR |= RCC_AHBENR_DMA1EN;
     volatile DMA_Channel_TypeDef *DMA = DMAs[idx];
+    uint32_t clkflags = 0;
     if(idx == 1){ // PA5/PA6; 72MHz
         RCC->APB2ENR |= RCC_APB2ENR_SPI1EN;
         RCC->APB2RSTR = RCC_APB2RSTR_SPI1RST;
         RCC->APB2RSTR = 0; // clear reset
         GPIOA->CRL = (GPIOA->CRL & ~(GPIO_CRL_CNF5 | GPIO_CRL_CNF6))
                      | CRL(5, CNF_AFPP|MODE_FAST) | CRL(6, CNF_FLINPUT);
-        SPI->CR1 = SPI_CR1_BR_1 | SPI_CR1_BR_2; // Fpclk/128
+        clkflags = ((uint32_t)the_conf.flags.BR) << 3;
         NVIC_EnableIRQ(DMA1_Channel2_IRQn); // enable Rx interrupt
     }else if(idx == 2){ // PB13/PB14; 36MHz
         RCC->APB1ENR |= RCC_APB1ENR_SPI2EN;
@@ -60,11 +62,14 @@ void spi_setup(uint8_t idx){
         RCC->APB1RSTR = 0;
         GPIOB->CRH = (GPIOB->CRH & ~(GPIO_CRH_CNF13 | GPIO_CRH_CNF14))
                      | CRH(13, CNF_AFPP|MODE_FAST) | CRH(14, CNF_FLINPUT);
-        SPI->CR1 = SPI_CR1_BR_0 | SPI_CR1_BR_2; // Fpclk/64
+        clkflags = ((uint32_t)the_conf.flags.BR - 1) << 3; // freq/2
         NVIC_EnableIRQ(DMA1_Channel4_IRQn);
     }else return; // err
     // Baudrate = 0b110 - fpclk/128
-    SPI->CR1 |= SPI_CR1_MSTR | SPI_CR1_SSM | SPI_CR1_SSI | SPI_CR1_RXONLY;
+    // CPOL=1 (CLK is 1 on idle); CPHA=0 (capture in first front)
+    if(the_conf.flags.CPHA) clkflags |= SPI_CR1_CPHA;
+    if(the_conf.flags.CPOL) clkflags |= SPI_CR1_CPOL;
+    SPI->CR1 |= SPI_CR1_MSTR | SPI_CR1_SSM | SPI_CR1_SSI | SPI_CR1_RXONLY | clkflags;
     SPI->CR2 = SPI_CR2_RXDMAEN;
     DMA->CPAR = (uint32_t)&(SPI->DR);
     DMA->CCR = DMA_CCR_MINC | DMA_CCR_TCIE | DMA_CCR_TEIE; // mem inc, hw->mem, Rx complete and error interrupt
@@ -76,8 +81,8 @@ void spi_onoff(uint8_t idx, uint8_t on){
     CHKIDX(idx);
     volatile SPI_TypeDef *SPI = SPIs[idx];
     if(on){
-        DBGs(u2str(idx));
-        DBG("turn on SPI");
+        //DBGs(u2str(idx));
+        //DBG("turn on SPI");
         SPI->CR1 |= SPI_CR1_SPE;
         spi_status[idx] = SPI_BUSY;
     }else{
@@ -117,9 +122,9 @@ static int spi_waitbsy(uint8_t idx){
 
 // just copy last read encoder value into `buf`
 // @return TRUE if got fresh data
-int spi_read_enc(uint8_t encno, uint8_t buf[8]){
+int spi_read_enc(uint8_t encno, uint8_t buf[ENCODER_BUFSZ]){
     if(encno > 1 || !freshdata[encno]) return FALSE;
-    DBGs(u2str(encno)); DBG("Read encoder data");
+    //DBGs(u2str(encno)); DBG("Read encoder data");
     memcpy(buf, encoderbuf[encno], ENCODER_BUFSZ);
     freshdata[encno] = 0; // clear fresh status
     return TRUE;
@@ -130,16 +135,16 @@ int spi_read_enc(uint8_t encno, uint8_t buf[8]){
 // here `encodernum` is 0 (SPI1) or 1 (SPI2), not 1/2 as SPI index!
 int spi_start_enc(int encodernum){
     int spiidx = encodernum + 1;
-    DBG("start enc");
+    //DBG("start enc");
     if(spiidx < 1 || spiidx > AMOUNT_OF_SPI) return FALSE;
     if(spi_status[spiidx] != SPI_READY) return FALSE;
     if(!spi_waitbsy(spiidx)) return FALSE;
-    if(SPI1->CR1 & SPI_CR1_SPE) DBG("spi1 works!");
-    if(SPI2->CR1 & SPI_CR1_SPE) DBG("spi2 works!");
+    if(SPI1->CR1 & SPI_CR1_SPE){ DBG("spi1 works!");}
+    if(SPI2->CR1 & SPI_CR1_SPE){ DBG("spi2 works!");}
     volatile DMA_Channel_TypeDef *DMA = DMAs[spiidx];
     DMA->CMAR = (uint32_t) encoderbuf[encodernum];
     DMA->CNDTR = ENCODER_BUFSZ;
-    DBG("turn on spi");
+    //DBG("turn on spi");
     spi_onoff(spiidx, 1);
     DMA->CCR |= DMA_CCR_EN;
     return TRUE;
@@ -149,6 +154,7 @@ int spi_start_enc(int encodernum){
 void dma1_channel2_isr(){
     // turn off DMA
     DMA1_Channel2->CCR &= ~DMA_CCR_EN;
+    SPI1->CR1 &= ~SPI_CR1_SPE;
     if(DMA1->ISR & DMA_ISR_TEIF2){
         DMA1->IFCR = DMA_IFCR_CTEIF2;
     }
@@ -160,12 +166,13 @@ void dma1_channel2_isr(){
         //encoderbuf[6] = (ctr >> 8 ) & 0xff;
         //encoderbuf[7] = (ctr >> 0 ) & 0xff;
     }
-    spi_onoff(1, 0);
+    spi_status[1] = SPI_READY;
 }
 
 void dma1_channel4_isr(){
     // turn off DMA
     DMA1_Channel4->CCR &= ~DMA_CCR_EN;
+    SPI2->CR1 &= ~SPI_CR1_SPE;
     if(DMA1->ISR & DMA_ISR_TEIF4){
         DMA1->IFCR = DMA_IFCR_CTEIF4;
     }
@@ -173,6 +180,6 @@ void dma1_channel4_isr(){
         DMA1->IFCR = DMA_IFCR_CTCIF4;
         freshdata[1] = 1;
     }
-    spi_onoff(2, 0);
+    spi_status[2] = SPI_READY;
 }
 
diff --git a/F1:F103/BISS_C_encoders/spi.h b/F1:F103/BISS_C_encoders/spi.h
index 950f771..f5a4f84 100644
--- a/F1:F103/BISS_C_encoders/spi.h
+++ b/F1:F103/BISS_C_encoders/spi.h
@@ -4,7 +4,7 @@
 
 #define AMOUNT_OF_SPI   (2)
 
-#define ENCODER_BUFSZ   (8)
+#define ENCODER_BUFSZ   (12)
 
 typedef enum{
     SPI_NOTREADY,
@@ -18,4 +18,4 @@ void spi_onoff(uint8_t idx, uint8_t on);
 void spi_deinit(uint8_t idx);
 void spi_setup(uint8_t idx);
 int spi_start_enc(int encodernum);
-int spi_read_enc(uint8_t encno, uint8_t buf[8]);
+int spi_read_enc(uint8_t encno, uint8_t buf[ENCODER_BUFSZ]);
diff --git a/F1:F103/BISS_C_encoders/usb_descr.c b/F1:F103/BISS_C_encoders/usb_descr.c
index 6237867..fd1688d 100644
--- a/F1:F103/BISS_C_encoders/usb_descr.c
+++ b/F1:F103/BISS_C_encoders/usb_descr.c
@@ -215,7 +215,7 @@ static void wr0(const uint8_t *buf, uint16_t size, uint16_t askedsize){
             // keep DTOGs, clear CTR_RX,TX, set TX VALID, leave stat_Rx
             USB->EPnR[0] = (epstatus & ~(USB_EPnR_CTR_RX|USB_EPnR_CTR_TX|USB_EPnR_STAT_RX))
                            ^ USB_EPnR_STAT_TX;
-            uint32_t ctr = 1000000;
+            uint32_t ctr = 10000;
             while(--ctr && (USB->ISTR & USB_ISTR_CTR) == 0){IWDG->KR = IWDG_REFRESH;};
             if((USB->ISTR & USB_ISTR_CTR) == 0){
                 return;
diff --git a/F1:F103/BISS_C_encoders/usb_descr.h b/F1:F103/BISS_C_encoders/usb_descr.h
index b2778f5..8c0ffd2 100644
--- a/F1:F103/BISS_C_encoders/usb_descr.h
+++ b/F1:F103/BISS_C_encoders/usb_descr.h
@@ -45,9 +45,9 @@
 #define USB_EP0BUFSZ    64
 // virtual
 #define USB_EP1BUFSZ    10
-// Rx/Tx EPs: (512-64-128)/14 rouded to 8
-#define USB_RXBUFSZ     16
-#define USB_TXBUFSZ     16
+// Rx/Tx EPs: (512-64-128)/6 rouded to 8
+#define USB_RXBUFSZ     40
+#define USB_TXBUFSZ     64
 
 // string descriptors
 enum{
diff --git a/F1:F103/BISS_C_encoders/usb_dev.c b/F1:F103/BISS_C_encoders/usb_dev.c
index 269ee14..d9bcdfc 100644
--- a/F1:F103/BISS_C_encoders/usb_dev.c
+++ b/F1:F103/BISS_C_encoders/usb_dev.c
@@ -60,8 +60,8 @@ static uint8_t obuf[bTotNumEndpoints][RBOUTSZ], ibuf[bTotNumEndpoints][RBINSZ];
 static volatile ringbuffer rbout[bTotNumEndpoints] = {OBUF(0), OBUF(1), OBUF(2)};
 #define IBUF(N)  {.data = ibuf[N], .length = RBINSZ, .head = 0, .tail = 0}
 static volatile ringbuffer rbin[bTotNumEndpoints] = {IBUF(0), IBUF(1), IBUF(2)};
-// last send data size
-static volatile int lastdsz[bTotNumEndpoints] = {0};
+// last send data size (<0 if USB transfer ready)
+static volatile int lastdsz[bTotNumEndpoints] = {-1, -1, -1};
 
 static void chkin(uint8_t ifno){
     if(bufovrfl[ifno]) return; // allow user to know that previous buffer was overflowed and cleared
@@ -82,13 +82,19 @@ static void chkin(uint8_t ifno){
 static void send_next(uint8_t ifno){
     uint8_t usbbuff[USB_TXBUFSZ];
     int buflen = RB_read((ringbuffer*)&rbout[ifno], (uint8_t*)usbbuff, USB_TXBUFSZ);
+    if(!CDCready[ifno]){
+        lastdsz[ifno] = -1;
+        return;
+    }
     if(buflen == 0){
-        if(lastdsz[ifno] == 64) EP_Write(1+ifno, NULL, 0); // send ZLP after 64 bits packet when nothing more to send
-        lastdsz[ifno] = 0;
+        if(lastdsz[ifno] == USB_TXBUFSZ){
+            EP_Write(1+ifno, NULL, 0); // send ZLP after 64 bits packet when nothing more to send
+            lastdsz[ifno] = 0;
+        }else lastdsz[ifno] = -1; // OK. User can start sending data
         return;
     }else if(buflen < 0){
         DBG("Buff busy");
-        lastdsz[ifno] = 0;
+        lastdsz[ifno] = -1;
         return;
     }
     DBG("Got data in buf");
@@ -140,11 +146,13 @@ void WEAK clstate_handler(uint8_t ifno, uint16_t val){
     DBGs(uhex2str(ifno));
     DBGs(uhex2str(val));
     CDCready[ifno] = val; // CONTROL_DTR | CONTROL_RTS -> interface connected; 0 -> disconnected
+    lastdsz[ifno] = -1;
 }
 
 // SEND_BREAK
 void WEAK break_handler(uint8_t ifno){
     CDCready[ifno] = 0;
+    lastdsz[ifno] = -1;
     DBG("break_handler()");
     DBGs(uhex2str(ifno));
 }
@@ -154,6 +162,7 @@ void WEAK break_handler(uint8_t ifno){
 void set_configuration(){
     DBG("set_configuration()");
     for(int i = 0; i < bTotNumEndpoints; ++i){
+        IWDG->KR = IWDG_REFRESH;
         int r = EP_Init(1+i, EP_TYPE_BULK, USB_TXBUFSZ, USB_RXBUFSZ, rxtx_handler);
         if(r){
             DBG("Can't init EP");
@@ -215,6 +224,7 @@ void usb_class_request(config_pack_t *req, uint8_t *data, uint16_t datalen){
 int USB_sendall(uint8_t ifno){
     while(lastdsz[ifno] > 0){
         if(!CDCready[ifno]) return FALSE;
+        IWDG->KR = IWDG_REFRESH;
     }
     return TRUE;
 }
@@ -224,13 +234,17 @@ int USB_send(uint8_t ifno, const uint8_t *buf, int len){
     if(!buf || !CDCready[ifno] || !len) return FALSE;
     DBG("USB_send");
     while(len){
+        if(!CDCready[ifno]) return FALSE;
+        IWDG->KR = IWDG_REFRESH;
         int a = RB_write((ringbuffer*)&rbout[ifno], buf, len);
         if(a > 0){
             len -= a;
             buf += a;
-        } else if (a < 0) continue; // do nothing if buffer is in reading state
-        if(lastdsz[ifno] == 0) send_next(ifno); // need to run manually - all data sent, so no IRQ on IN
+        }else if(a == 0){ // overfull
+            if(lastdsz[ifno] < 0) send_next(ifno);
+        }
     }
+    if(buf[len-1] == '\n' && lastdsz[ifno] < 0) send_next(ifno);
     return TRUE;
 }
 
@@ -238,9 +252,15 @@ int USB_putbyte(uint8_t ifno, uint8_t byte){
     if(!CDCready[ifno]) return FALSE;
     int l = 0;
     while((l = RB_write((ringbuffer*)&rbout[ifno], &byte, 1)) != 1){
-        if(l < 0) continue;
+        if(!CDCready[ifno]) return FALSE;
+        IWDG->KR = IWDG_REFRESH;
+        if(l == 0){ // overfull
+            if(lastdsz[ifno] < 0) send_next(ifno);
+            continue;
+        }
     }
-    if(lastdsz[ifno] == 0) send_next(ifno); // need to run manually - all data sent, so no IRQ on IN
+    // send line if got EOL
+    if(byte == '\n' && lastdsz[ifno] < 0) send_next(ifno);
     return TRUE;
 }
 
diff --git a/F1:F103/BISS_C_encoders/usb_dev.h b/F1:F103/BISS_C_encoders/usb_dev.h
index a785895..7f32ac6 100644
--- a/F1:F103/BISS_C_encoders/usb_dev.h
+++ b/F1:F103/BISS_C_encoders/usb_dev.h
@@ -48,8 +48,8 @@ void linecoding_handler(uint8_t ifno, usb_LineCoding *lc);
 
 
 // sizes of ringbuffers for outgoing and incoming data
-#define RBOUTSZ     (256)
-#define RBINSZ      (256)
+#define RBOUTSZ     (512)
+#define RBINSZ      (128)
 
 #define newline(ifno)   USB_putbyte(ifno, '\n')
 #define USND(ifno, s)   do{USB_sendstr(ifno, s); USB_putbyte(ifno, '\n');}while(0)
@@ -61,7 +61,7 @@ void linecoding_handler(uint8_t ifno, usb_LineCoding *lc);
 #define STR_HELPER(s)   #s
 #define STR(s)          STR_HELPER(s)
 #define DBG(str)  do{USB_sendstr(I_CMD, __FILE__ " (L" STR(__LINE__) "): " str); USB_putbyte(I_CMD, '\n');}while(0)
-#define DBGs(str) do{USB_sendstr(I_CMD, str); USB_sendstr(I_CMD, "<--\n");}while(0)
+#define DBGs(str) do{USB_sendstr(I_CMD, str); USB_sendstr(I_CMD, "\n");}while(0)
 #else
 #define DBG(s)
 #define DBGs(s)
diff --git a/F1:F103/BISS_C_encoders/version.inc b/F1:F103/BISS_C_encoders/version.inc
index 2872e58..2bcb422 100644
--- a/F1:F103/BISS_C_encoders/version.inc
+++ b/F1:F103/BISS_C_encoders/version.inc
@@ -1,2 +1,2 @@
-#define BUILD_NUMBER "73"
-#define BUILD_DATE "2025-03-27"
+#define BUILD_NUMBER "91"
+#define BUILD_DATE "2025-04-02"