diff --git a/F3:F303/Multistepper/Readme.md b/F3:F303/Multistepper/Readme.md
index 64abe75..d3f5790 100644
--- a/F3:F303/Multistepper/Readme.md
+++ b/F3:F303/Multistepper/Readme.md
@@ -221,4 +221,13 @@ _SW_ used as debugging/sewing; also (I remember about USB pullup only after end
 
 * ADC1 - DMA1_ch1
 * ADC2 - DMA2_ch1
+* USART2 (PDN-UART for drivers 0..3) - DMA1_ch6 (Rx), DMA1_ch7 (Tx)
+* USART3 (PDN-UART for drivers 4..7) - DMA1_ch3 (Rx), DMA1_ch2 (Tx)
+* SPI2 (screen) - DMA1_ch4 (Rx), DMA1_ch5 (Tx) [or may be dedicated to USART1]
 
+# Other stepper drivers connection
+
+## DRV8825
+Solder jumpers E2, B and A to connect ~RST and ~SLP to 3.3V.
+
+Microstepping selection produced by soldering H2 (bit0), G2 (bit1) and/or C (bit2).
\ No newline at end of file
diff --git a/F3:F303/Multistepper/hardware.c b/F3:F303/Multistepper/hardware.c
index 832826b..ae1433e 100644
--- a/F3:F303/Multistepper/hardware.c
+++ b/F3:F303/Multistepper/hardware.c
@@ -124,7 +124,8 @@ TRUE_INLINE void gpio_setup(){
                  | MODER_AF(14) | MODER_AF(15);
     GPIOB->OSPEEDR = OSPEED_HI(0) | OSPEED_HI(5) | OSPEED_HI(8) | OSPEED_MED(13) | OSPEED_MED(14) | OSPEED_MED(15);
     GPIOB->OTYPER = 0;
-    GPIOB->PUPDR = PUPD_PU(7) | PUPD_PU(9) | PUPD_PU(11);
+    // USART2_Tx (PB3) and USART3_Tx (PB10) are also pullup
+    GPIOB->PUPDR = PUPD_PU(3) | PUPD_PU(7) | PUPD_PU(9) | PUPD_PU(7) | PUPD_PU(11);
 
     GPIOC->ODR = 0;
     GPIOC->AFR[0] = AFRf(7, 4) | AFRf(7, 5) | AFRf(4, 6);
diff --git a/F3:F303/Multistepper/main.c b/F3:F303/Multistepper/main.c
index 9570776..5ab68e5 100644
--- a/F3:F303/Multistepper/main.c
+++ b/F3:F303/Multistepper/main.c
@@ -21,6 +21,7 @@
 #include "can.h"
 #include "flash.h"
 #include "hardware.h"
+#include "pdnuart.h"
 #include "proto.h"
 #include "steppers.h"
 #include "usb.h"
@@ -86,5 +87,6 @@ int main(void){
             if(ans) USB_sendstr(ans);
         }
         process_keys();
+        pdnuart_poll();
     }
 }
diff --git a/F3:F303/Multistepper/multistepper.bin b/F3:F303/Multistepper/multistepper.bin
index 3864bcf..36b0a98 100755
Binary files a/F3:F303/Multistepper/multistepper.bin and b/F3:F303/Multistepper/multistepper.bin differ
diff --git a/F3:F303/Multistepper/multistepper.files b/F3:F303/Multistepper/multistepper.files
index 2e2b09c..0202d6d 100644
--- a/F3:F303/Multistepper/multistepper.files
+++ b/F3:F303/Multistepper/multistepper.files
@@ -15,6 +15,8 @@ hashgen/hdr.c
 hashgen/hdr.h
 hashgen/test.c
 main.c
+pdnuart.c
+pdnuart.h
 proto.c
 proto.h
 ringbuffer.c
diff --git a/F3:F303/Multistepper/pdnuart.c b/F3:F303/Multistepper/pdnuart.c
new file mode 100644
index 0000000..4621c47
--- /dev/null
+++ b/F3:F303/Multistepper/pdnuart.c
@@ -0,0 +1,230 @@
+/*
+ * This file is part of the multistepper project.
+ * Copyright 2023 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 <stm32f3.h>
+
+#include "hardware.h"
+#include "proto.h"
+
+extern volatile uint32_t Tms;
+
+#define MAXBUFLEN           (8)
+// Rx timeout, ms
+#define PDNUART_TIMEOUT     (20)
+
+// buffers format: 0 - sync+reserved, 1 - address (0..3 - slave, 0xff - master)
+//      2 - register<<1 | RW, 3 - CRC (r) or [ 3..6 - MSB data, 7 - CRC ]
+// buf[0] - USART2, buf[1] - USART3
+static uint8_t inbuf[2][MAXBUFLEN], outbuf[2][MAXBUFLEN];
+static uint8_t Taccess[2] = {0}; // last access time
+static int curslaveaddr[2] = {-1, -1}; // current slave address for each USART (0..3)
+static uint8_t notfound = 0; // not found mask (LSB - 0, MSB - 7)
+static uint8_t readrq[2] = {0}; // ==1 for read request (after send wait to read)
+
+// UART states
+typedef enum{
+    PDU_IDLE,
+    PDU_TX,
+    PDU_TXREADY,
+    PDU_RX,
+    PDU_RXREADY
+} pdnuart_state;
+static pdnuart_state state[2] = {PDU_IDLE, PDU_IDLE};
+
+// datalen == 3 for read request or 7 for writing
+static void calcCRC(int no, int datalen){
+    uint8_t crc = 0;
+    for(int i = 0; i < datalen; ++i){
+        uint8_t currentByte = outbuf[no][i];
+        for(int j = 0; j < 8; ++j){
+            if((crc >> 7) ^ (currentByte & 0x01)) crc = (crc << 1) ^ 0x07;
+            else crc <<= 1;
+            currentByte = currentByte >> 1;
+        }
+    }
+    outbuf[no][datalen] = crc;
+}
+
+static volatile DMA_Channel_TypeDef *TxDMA[2] = {DMA1_Channel7, DMA1_Channel2};
+static volatile DMA_Channel_TypeDef *RxDMA[2] = {DMA1_Channel6, DMA1_Channel3};
+static volatile USART_TypeDef *USART[2] = {USART2, USART3};
+
+static void setup_usart(int no){
+    USART[no]->ICR = 0xffffffff; // clear all flags
+    TxDMA[no]->CCR = 0;
+    TxDMA[no]->CPAR = (uint32_t) &USART[no]->TDR; // periph
+    TxDMA[no]->CCR |= DMA_CCR_MINC | DMA_CCR_DIR | DMA_CCR_TCIE; // 8bit, mem++, mem->per, transcompl irq
+    RxDMA[no]->CCR = 0;
+    RxDMA[no]->CPAR = (uint32_t) &USART[no]->RDR; // periph
+    RxDMA[no]->CCR |= DMA_CCR_MINC | DMA_CCR_TCIE; // 8bit, mem++, per->mem, transcompl irq
+    USART[no]->BRR = 72000000 / 256000; // 256 kbaud
+    USART[no]->CR3 = USART_CR3_DMAT | USART_CR3_DMAR; // enable DMA Tx/Rx
+    USART[no]->CR1 = USART_CR1_TE | USART_CR1_RE | USART_CR1_UE; // 1start,8data,nstop; enable Rx,Tx,USART
+    uint32_t tmout = 16000000;
+    while(!(USART[no]->ISR & USART_ISR_TC)){if(--tmout == 0) break;} // polling idle frame Transmission
+    USART[no]->ICR = 0xffffffff; // clear all flags again
+}
+
+// USART2 (ch0..3): DMA1ch6 (Rx), DMA1_ch7 (Tx)
+// USART3 (ch4..7): DMA1ch3 (Rx), DMA1_ch2 (Tx)
+// pins are setting up in `hardware.c`
+void pdnuart_setup(){
+    RCC->APB1ENR |= RCC_APB1ENR_USART2EN | RCC_APB1ENR_USART3EN;
+    RCC->AHBENR |= RCC_AHBENR_DMA1EN;
+    setup_usart(0);
+    setup_usart(1);
+    NVIC_EnableIRQ(DMA1_Channel2_IRQn);
+    NVIC_EnableIRQ(DMA1_Channel3_IRQn);
+    NVIC_EnableIRQ(DMA1_Channel6_IRQn);
+    NVIC_EnableIRQ(DMA1_Channel7_IRQn);
+}
+
+static int rwreg(uint8_t motorno, uint8_t reg, uint32_t data, int w){
+    if(motorno >= MOTORSNO || reg & 0x80) return FALSE;
+    int no = motorno >> 2;
+    if(state[no] != PDU_IDLE) return FALSE;
+    outbuf[no][0] = 0xa0;
+    outbuf[no][1] = curslaveaddr[no] = motorno - (no << 2);
+    outbuf[no][2] = reg << 1;
+    int nbytes = 3;
+    if(w){
+        outbuf[no][2] |= 1;
+        for(int i = 6; i > 2; --i){
+            outbuf[no][i] = data & 0xff;
+            data >>= 8;
+        }
+        nbytes = 7;
+        readrq[no] = 0;
+    }else{
+        readrq[no] = 1;
+    }
+    calcCRC(no, nbytes);
+    TxDMA[no]->CMAR = (uint32_t) outbuf[no];
+    TxDMA[no]->CNDTR = nbytes + 1;
+    TxDMA[no]->CCR |= DMA_CCR_EN; // start transmission
+    state[no] = PDU_TX;
+    Taccess[no] = Tms;
+    return TRUE;
+}
+
+// return FALSE if failed
+int pdnuart_writereg(uint8_t motorno, uint8_t reg, uint32_t data){
+    return rwreg(motorno, reg, data, 1);
+}
+
+// return FALSE if failed
+int pdnuart_readreg(uint8_t motorno, uint8_t reg){
+    return rwreg(motorno, reg, 0, 0);
+}
+
+static void disableDMA(int no){
+    TxDMA[no]->CCR &= ~DMA_CCR_EN;
+    RxDMA[no]->CCR &= ~DMA_CCR_EN;
+    readrq[no] = 0;
+    state[no] = PDU_IDLE;
+}
+
+static void parseRx(int no){
+    USB_sendstr("Got from ");
+    USB_putbyte('#'); printu(curslaveaddr[no] + no*4); USB_sendstr(": ");
+    for(int i = 0; i < 8; ++i){
+        printuhex(inbuf[no][i]); USB_putbyte(' ');
+    }
+    newline();
+}
+
+void pdnuart_poll(){
+    for(int i = 0; i < 2; ++i){
+        int showno = 0;
+        uint32_t time = Tms - Taccess[i];
+        switch(state[i]){
+            case PDU_TX:
+                if(time > PDNUART_TIMEOUT){
+                    USB_sendstr("PDN/UART timeout: Tx problem ");
+                    showno = 1;
+                    disableDMA(i);
+                }
+            break;
+            case PDU_TXREADY:
+                USB_sendstr("Tx ready ");
+                showno = 1;
+            break;
+            case PDU_RX:
+                if(time > PDNUART_TIMEOUT){
+                    USB_sendstr("PDN/UART timeout: no answer ");
+                    notfound |= 1 << (curslaveaddr[i] + 4*i);
+                    showno = 1;
+                    disableDMA(i);
+                }
+            break;
+            case PDU_RXREADY:
+                parseRx(i);
+                state[i] = PDU_IDLE; // DMA already turned off
+            break;
+            default: // IDLE
+            return;
+        }
+        if(showno){
+            USB_putbyte('#'); printu(curslaveaddr[i] + 4*i); newline();
+        }
+    }
+}
+
+// USART2 Tx complete -> prepare Rx
+void dma1_channel7_isr(){
+    DMA1_Channel7->CCR &= ~DMA_CCR_EN;
+    DMA1->IFCR |= DMA_IFCR_CTCIF7;
+    if(!readrq[0]){ // there was a setter
+        state[0] = PDU_TXREADY;
+        return;
+    }
+    DMA1_Channel6->CMAR = (uint32_t) inbuf[0];
+    DMA1_Channel6->CCR |= DMA_CCR_EN;
+    DMA1_Channel6->CNDTR = MAXBUFLEN;
+    state[0] = PDU_RX;
+    Taccess[0] = Tms;
+}
+
+// USART3 Tx complete -> prepare Rx
+void dma1_channel2_isr(){
+    DMA1_Channel2->CCR &= ~DMA_CCR_EN;
+    DMA1->IFCR |= DMA_IFCR_CTCIF2;
+    if(!readrq[1]){ // there was a setter
+        state[1] = PDU_TXREADY;
+        return;
+    }
+    DMA1_Channel3->CMAR = (uint32_t) inbuf[1];
+    DMA1_Channel3->CCR |= DMA_CCR_EN;
+    DMA1_Channel3->CNDTR = MAXBUFLEN;
+    state[1] = PDU_RX;
+    Taccess[1] = Tms;
+}
+
+// USART2 Rx complete -> set flag
+void dma1_channel6_isr(){
+    DMA1_Channel6->CCR &= ~DMA_CCR_EN;
+    DMA1->IFCR |= DMA_IFCR_CTCIF6;
+    state[0] = PDU_RXREADY;
+}
+
+// USART3 Rx complete -> set flag
+void dma1_channel3_isr(){
+    DMA1_Channel3->CCR &= ~DMA_CCR_EN;
+    DMA1->IFCR |= DMA_IFCR_CTCIF3;
+    state[1] = PDU_RXREADY;
+}
diff --git a/F3:F303/Multistepper/pdnuart.h b/F3:F303/Multistepper/pdnuart.h
new file mode 100644
index 0000000..8934025
--- /dev/null
+++ b/F3:F303/Multistepper/pdnuart.h
@@ -0,0 +1,26 @@
+/*
+ * This file is part of the multistepper project.
+ * Copyright 2023 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>
+
+void pdnuart_poll();
+void pdnuart_setup();
+int pdnuart_writereg(uint8_t motorno, uint8_t reg, uint32_t data);
+int pdnuart_readreg(uint8_t motorno, uint8_t reg);
diff --git a/F3:F303/Multistepper/version.inc b/F3:F303/Multistepper/version.inc
index e4c2362..7a4469e 100644
--- a/F3:F303/Multistepper/version.inc
+++ b/F3:F303/Multistepper/version.inc
@@ -1,2 +1,2 @@
-#define BUILD_NUMBER "80"
-#define BUILD_DATE "2023-02-24"
+#define BUILD_NUMBER "82"
+#define BUILD_DATE "2023-02-25"