ATmega328P U-TH can't burn bootloader

Hi,

This might sound like a repeat of an often reported problem, but hear me out please.
For my hobby project, I made a custom board with schematic similar to that of Arduino pro mini. It controls a MOSFET based on an IR signal.
ATmega328P U-TH Vcc, AVcc tied together, 0.1uF cap between ARef and GND. 8MHz crystal between XTAL1 and XTAL2 with 22pF caps between crystal pins and GND.

I have been trying to burn the "Pro Mini 3.3v/8MHz" bootloader via MISO-MOSI-SCK-RST pins, and am getting this error:

avrdude: Device signature = 0x000000
avrdude: Yikes! Invalid device signature.
Double check connections and try again, or use -F to override
this check.

All the forums where this error is reported point towards a wiring/hardware problem. So I checked all the connections multiple times. No short between any of the lines and Vcc/GND. Continuity between the programming board pins (Nano as ISP) and the ATmega328 pins is fine.

Checked the crystal pins for any frequency while the IC is powered, it shown none.
Tried with the modified ISP sketch with 8MHz signal on pin 9, same error.
Tried to read fuses with Nick Gammon's fuse calculator sketch, getting this output:

Attempting to enter programming mode ......................................................
Failed to enter programming mode. Double-check wiring!

At this point, I feel the IC is faulty. But again, none of the forums I read had this outcome. Everywhere it was a small hardware/wiring problem. I can't find mine. Spent 14 hours debugging it, my eyes are burning and feels like my head is going to explode.

Just seeking directions on any possibility I missed, or a pointer to the IC indeed being faulty.

PS - I don't have an oscilloscope and rework station. So checking signals and removing the IC is hard.
Attaching the Atmega part of the schematic.

And you are connecting the RST pin in your ICSP connector on your board to pin 10 on your promini programmer?

Can you burn the bootloader on another promini with your promini programmer without problems?

You are not connecting a 5V promini programmer to a 3.3V target ?

Just a guess; you could try lower the SPI Clock even more. It should be ok for a factory fresh Atmega328 that is clocked at 1MHz internal, but I had rare occasions where a slower clock woke it up when programming at 3.3V.

Look in the ArduinoISP sketch for


// Configure SPI clock (in Hz).
// E.g. for an ATtiny @ 128 kHz: the datasheet states that both the high and low
// SPI clock pulse must be > 2 CPU cycles, so take 3 cycles i.e. divide target
// f_cpu by 6:
//     #define SPI_CLOCK            (128000/6)
//
// A clock slow enough for an ATtiny85 @ 1 MHz, is a reasonable default:

#define SPI_CLOCK 		(1000000/6)

and uncomment the slower SPI_CLOCK and comment the 1MHz / 6 SPI_CLOCK

Hi. Thanks for the response.

And you are connecting the RST pin in your ICSP connector on your board to pin 10 on your promini programmer?
Yes

Can you burn the bootloader on another promini with your promini programmer without problems?

Have ordered a new pro mini. Unfortunately, it will take a few days to arrive.

You are not connecting a 5V promini programmer to a 3.3V target ?

The programmer is an Arduino Nano, 5v. But the target circuit runs on 3.3V. I tried to program with both the 3v3 and 5v pins of the programmer to ICSP Vcc pin with the same outcome.

Just a guess; you could try lower the SPI Clock even more.

I didn't try that, will test this one too and will post the outcome here.

Tried and failed:

         Using Port                    : COM3
         Using Programmer              : stk500v1
         Overriding Baud Rate          : 19200
         AVR Part                      : ATmega328P
         Chip Erase delay              : 9000 us
         PAGEL                         : PD7
         BS2                           : PC2
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom        65    20     4    0 no       1024    4      0  3600  3600 0xff 0xff
           flash         65     6   128    0 yes     32768  128    256  4500  4500 0xff 0xff
           lfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           efuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           lock           0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00

         Programmer Type : STK500
         Description     : Atmel STK500 Version 1.x firmware
         Hardware Version: 2
         Firmware Version: 1.18
         Topcard         : Unknown
         Vtarget         : 0.0 V
         Varef           : 0.0 V
         Oscillator      : Off
         SCK period      : 0.1 us

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.02s

avrdude: Device signature = 0x000000 (retrying)

Reading | ################################################## | 100% 0.02s

avrdude: Device signature = 0x000000 (retrying)

Reading | ################################################## | 100% 0.02s

avrdude: Device signature = 0x000000
avrdude: Yikes!  Invalid device signature.
         Double check connections and try again, or use -F to override
         this check.


avrdude done.  Thank you.

Failed chip erase: uploading error: exit status 1

Ok, I created the entire setup afresh.
This time, a new Uno is the ISP loaded with ISP sketch from the examples.
Target device is the Nano which I was originally using as an ISP.
No breadboard this time (with Nano as ISP, I was using a breadboard to hold the Nano).
All new jumper wires.

Tried to burn the bootloader into the Nano, it failed with the same error (Device signature = 0x000000)!
Then tried with an old version of Arduino IDE, same problem. Switched between 3V3 and 5V supplies to the Nano, again the same result.
I suspected the Nano to be the culprit (Nano is the only piece, beside myself, which was there in both the new and the old setup). So, removed the Nano and tried to burn the bootloader into my original board, and again the same error.

Checked all the wiring, pinouts, continuities, even changed the USB cable and the USB ports, switched between IDE on Windows and Linux, all to no avail.
Makes me think I am doing something really dumb and somehow not able to catch it.

There have been several discussions as to whether the U-TH is fake or not.
It's not a part number listed by microchip.
If you did not purchased from a Microchip authorized reseller, it is probably fake.
I notice that in your schematic you are using a -AU which is a valid part.

Well yes. Had that thought and I read almost every post about these ICs when mine didn't work. There is no consensus.
The problem now is, when I tried to burn a bootloader into a working Arduino board (a Nano clone), other than my custom U-TH board, I got the same error. So most likely I am doing something wrong here, just can't figure out what it is.

I have used these U-TH ICs in the past, they do work. It seems these are the only ones available in my country. Even if you order an AU, you actually get a U-TH.

Probably but unfortunately we can't see what you are doing, so can't help much
Maybe take a break.

I understand. Thanks for all the help so far.
Have been five days at it, really need a break. Will resume on Monday!

Good idea.
Sometimes you can stare at something all day and not see the obvious. Been there.

I'm surprized as you. So to triple check, this is how you wire it up?

Slightly different, on Uno side I am not using the ICSP header. Using the Uno I/O pins instead:

So looks like this:

That wiring looks ok to me. Works on my CH340G based board.

The only thing I can think of to try: stick a approximately 10uF capacitor between the GND and RST pin in your UNO. This should prevent it from a possible reset if the serial port gets active during programming. Mine works fine without, but who knows.

Thanks! Tried, again the same error. Only thing left to try now is an IDE on a different computer.

Ok, I am out of clues now. Maybe one of the SPI pins (Mosi, Miso, Sck) on your nano is blown. Those are used in both cases as programmer or being the target.

Will test once the new Pro Mini arrives to eliminate the Nano entirely.

Also, to eliminate CH340 out of suspects list, I reinstalled CH340 drivers, used a USBAsp, tried on a different PC (though both PCs run Win11, Linux is not possible anymore as after Ubuntu 24.04 update, Arduino AppImage does not run anymore).
One thing I noticed is that the Nano power LED barely lights up when connected via ICSP. You can see that in the photograph in my previous reply, Uno's LED are bright red but Nano's aren't even visible.

Maybe a power issue (though additional power to Nano through USB didn't work either). I measures the jumper wires, those are around 20cm, and have close to 1 Ohm resistance. Don't think that should make much difference.

Anyway, thank you hmeijdam and jim-p for all the help! Really appreciate you giving time to my problem.
If I find a solution or a root-cause, I will come back and post the details. In the meantime, any idea is welcome.

Ahhhh....

You better check if that clone nano doesn't have its ICSP header backwards or mirrored on it's PCB.

Try connecting to the pins on it's bottom instead, like you did with the UNO.

Looking at your picture instead of your drawing I think you wired it wrong to the ICSP header. You need to rotate 180 degrees.

Arduino-nano-ICSP-Pins

You are right!
I rewired it the way you advised, the LEDs light up.
But, the problem of invalid signature remains. I even tried on a new Nano, with the same results.

Could it be that the Arduino as ISP sketch has been updated to a new version, which does not work with my old devices? (These Arduinos were purchased around 2019-2020, and could be even older if the seller had old stock). At this point, I'd suspect everything, from incompatible sketch to static charge on my desk!

Unlikely. I have 10 year old Uno's and Nano's that behave exacly like new ones. As long as they have a Atmega328/168 you are good.
Thinking about that, can you post a sharp closeup picture of the Nano's? Curious to see the markings on the Atmega's

FWIW this is the ArduinoISP sketch I used.

// ArduinoISP
// Copyright (c) 2008-2011 Randall Bohn
// If you require a license, see
// https://opensource.org/licenses/bsd-license.php
//
// This sketch turns the Arduino into a AVRISP using the following Arduino pins:
//
// Pin 10 is used to reset the target microcontroller.
//
// By default, the hardware SPI pins MISO, MOSI and SCK are used to communicate
// with the target. On all Arduinos, these pins can be found
// on the ICSP/SPI header:
//
//               MISO °. . 5V (!) Avoid this pin on Due, Zero...
//               SCK   . . MOSI
//                     . . GND
//
// On some Arduinos (Uno,...), pins MOSI, MISO and SCK are the same pins as
// digital pin 11, 12 and 13, respectively. That is why many tutorials instruct
// you to hook up the target to these pins. If you find this wiring more
// practical, have a define USE_OLD_STYLE_WIRING. This will work even when not
// using an Uno. (On an Uno this is not needed).
//
// Alternatively you can use any other digital pin by configuring
// software ('BitBanged') SPI and having appropriate defines for PIN_MOSI,
// PIN_MISO and PIN_SCK.
//
// IMPORTANT: When using an Arduino that is not 5V tolerant (Due, Zero, ...) as
// the programmer, make sure to not expose any of the programmer's pins to 5V.
// A simple way to accomplish this is to power the complete system (programmer
// and target) at 3V3.
//
// Put an LED (with resistor) on the following pins:
// 9: Heartbeat   - shows the programmer is running
// 8: Error       - Lights up if something goes wrong (use red if that makes sense)
// 7: Programming - In communication with the slave
//

#include "Arduino.h"
#undef SERIAL


#define PROG_FLICKER true

// Configure SPI clock (in Hz).
// E.g. for an ATtiny @ 128 kHz: the datasheet states that both the high and low
// SPI clock pulse must be > 2 CPU cycles, so take 3 cycles i.e. divide target
// f_cpu by 6:
//     #define SPI_CLOCK            (128000/6)
//
// A clock slow enough for an ATtiny85 @ 1 MHz, is a reasonable default:

#define SPI_CLOCK 		(1000000/6)


// Select hardware or software SPI, depending on SPI clock.
// Currently only for AVR, for other architectures (Due, Zero,...), hardware SPI
// is probably too fast anyway.

#if defined(ARDUINO_ARCH_AVR)

  #if SPI_CLOCK > (F_CPU / 128)
    #define USE_HARDWARE_SPI
  #endif

#endif

// Configure which pins to use:

// The standard pin configuration.
#ifndef ARDUINO_HOODLOADER2

  #define RESET     10 // Use pin 10 to reset the target rather than SS
  #define LED_HB    9
  #define LED_ERR   8
  #define LED_PMODE 7

  // Uncomment following line to use the old Uno style wiring
  // (using pin 11, 12 and 13 instead of the SPI header) on Leonardo, Due...

  // #define USE_OLD_STYLE_WIRING

  #ifdef USE_OLD_STYLE_WIRING

    #define PIN_MOSI	11
    #define PIN_MISO	12
    #define PIN_SCK		13

  #endif

  // HOODLOADER2 means running sketches on the ATmega16U2 serial converter chips
  // on Uno or Mega boards. We must use pins that are broken out:
#else

  #define RESET     	4
  #define LED_HB    	7
  #define LED_ERR   	6
  #define LED_PMODE 	5

#endif

// By default, use hardware SPI pins:
#ifndef PIN_MOSI
  #define PIN_MOSI 	MOSI
#endif

#ifndef PIN_MISO
  #define PIN_MISO 	MISO
#endif

#ifndef PIN_SCK
  #define PIN_SCK 	SCK
#endif

// Force bitbanged SPI if not using the hardware SPI pins:
#if (PIN_MISO != MISO) ||  (PIN_MOSI != MOSI) || (PIN_SCK != SCK)
  #undef USE_HARDWARE_SPI
#endif


// Configure the serial port to use.
//
// Prefer the USB virtual serial port (aka. native USB port), if the Arduino has one:
//   - it does not autoreset (except for the magic baud rate of 1200).
//   - it is more reliable because of USB handshaking.
//
// Leonardo and similar have an USB virtual serial port: 'Serial'.
// Due and Zero have an USB virtual serial port: 'SerialUSB'.
//
// On the Due and Zero, 'Serial' can be used too, provided you disable autoreset.
// To use 'Serial': #define SERIAL Serial

#ifdef SERIAL_PORT_USBVIRTUAL
  #define SERIAL SERIAL_PORT_USBVIRTUAL
#else
  #define SERIAL Serial
#endif


// Configure the baud rate:

#define BAUDRATE	19200
// #define BAUDRATE	115200
// #define BAUDRATE	1000000


#define HWVER 2
#define SWMAJ 1
#define SWMIN 18

// STK Definitions
#define STK_OK      0x10
#define STK_FAILED  0x11
#define STK_UNKNOWN 0x12
#define STK_INSYNC  0x14
#define STK_NOSYNC  0x15
#define CRC_EOP     0x20 //ok it is a space...

void pulse(int pin, int times);

#ifdef USE_HARDWARE_SPI
#include "SPI.h"
#else

#define SPI_MODE0 0x00

#if !defined(ARDUINO_API_VERSION) || ARDUINO_API_VERSION != 10001 // A SPISettings class is declared by ArduinoCore-API 1.0.1
class SPISettings {
  public:
    // clock is in Hz
    SPISettings(uint32_t clock, uint8_t bitOrder, uint8_t dataMode) : clockFreq(clock) {
      (void) bitOrder;
      (void) dataMode;
    };

    uint32_t getClockFreq() const {
      return clockFreq;
    }

  private:
    uint32_t clockFreq;
};
#endif  // !defined(ARDUINO_API_VERSION)

class BitBangedSPI {
  public:
    void begin() {
      digitalWrite(PIN_SCK, LOW);
      digitalWrite(PIN_MOSI, LOW);
      pinMode(PIN_SCK, OUTPUT);
      pinMode(PIN_MOSI, OUTPUT);
      pinMode(PIN_MISO, INPUT);
    }

    void beginTransaction(SPISettings settings) {
      pulseWidth = (500000 + settings.getClockFreq() - 1) / settings.getClockFreq();
      if (pulseWidth == 0) {
        pulseWidth = 1;
      }
    }

    void end() {}

    uint8_t transfer(uint8_t b) {
      for (unsigned int i = 0; i < 8; ++i) {
        digitalWrite(PIN_MOSI, (b & 0x80) ? HIGH : LOW);
        digitalWrite(PIN_SCK, HIGH);
        delayMicroseconds(pulseWidth);
        b = (b << 1) | digitalRead(PIN_MISO);
        digitalWrite(PIN_SCK, LOW); // slow pulse
        delayMicroseconds(pulseWidth);
      }
      return b;
    }

  private:
    unsigned long pulseWidth; // in microseconds
};

static BitBangedSPI SPI;

#endif

void setup() {
  SERIAL.begin(BAUDRATE);

  pinMode(LED_PMODE, OUTPUT);
  pulse(LED_PMODE, 2);
  pinMode(LED_ERR, OUTPUT);
  pulse(LED_ERR, 2);
  pinMode(LED_HB, OUTPUT);
  pulse(LED_HB, 2);

}

int ISPError = 0;
int pmode = 0;
// address for reading and writing, set by 'U' command
unsigned int here;
uint8_t buff[256]; // global block storage

#define beget16(addr) (*addr * 256 + *(addr+1) )
typedef struct param {
  uint8_t devicecode;
  uint8_t revision;
  uint8_t progtype;
  uint8_t parmode;
  uint8_t polling;
  uint8_t selftimed;
  uint8_t lockbytes;
  uint8_t fusebytes;
  uint8_t flashpoll;
  uint16_t eeprompoll;
  uint16_t pagesize;
  uint16_t eepromsize;
  uint32_t flashsize;
}
parameter;

parameter param;

// this provides a heartbeat on pin 9, so you can tell the software is running.
uint8_t hbval = 128;
int8_t hbdelta = 8;
void heartbeat() {
  static unsigned long last_time = 0;
  unsigned long now = millis();
  if ((now - last_time) < 40) {
    return;
  }
  last_time = now;
  if (hbval > 192) {
    hbdelta = -hbdelta;
  }
  if (hbval < 32) {
    hbdelta = -hbdelta;
  }
  hbval += hbdelta;
  analogWrite(LED_HB, hbval);
}

static bool rst_active_high;

void reset_target(bool reset) {
  digitalWrite(RESET, ((reset && rst_active_high) || (!reset && !rst_active_high)) ? HIGH : LOW);
}

void loop(void) {
  // is pmode active?
  if (pmode) {
    digitalWrite(LED_PMODE, HIGH);
  } else {
    digitalWrite(LED_PMODE, LOW);
  }
  // is there an error?
  if (ISPError) {
    digitalWrite(LED_ERR, HIGH);
  } else {
    digitalWrite(LED_ERR, LOW);
  }

  // light the heartbeat LED
  heartbeat();
  if (SERIAL.available()) {
    avrisp();
  }
}

uint8_t getch() {
  while (!SERIAL.available());
  return SERIAL.read();
}
void fill(int n) {
  for (int x = 0; x < n; x++) {
    buff[x] = getch();
  }
}

#define PTIME 30
void pulse(int pin, int times) {
  do {
    digitalWrite(pin, HIGH);
    delay(PTIME);
    digitalWrite(pin, LOW);
    delay(PTIME);
  } while (times--);
}

void prog_lamp(int state) {
  if (PROG_FLICKER) {
    digitalWrite(LED_PMODE, state);
  }
}

uint8_t spi_transaction(uint8_t a, uint8_t b, uint8_t c, uint8_t d) {
  SPI.transfer(a);
  SPI.transfer(b);
  SPI.transfer(c);
  return SPI.transfer(d);
}

void empty_reply() {
  if (CRC_EOP == getch()) {
    SERIAL.print((char)STK_INSYNC);
    SERIAL.print((char)STK_OK);
  } else {
    ISPError++;
    SERIAL.print((char)STK_NOSYNC);
  }
}

void breply(uint8_t b) {
  if (CRC_EOP == getch()) {
    SERIAL.print((char)STK_INSYNC);
    SERIAL.print((char)b);
    SERIAL.print((char)STK_OK);
  } else {
    ISPError++;
    SERIAL.print((char)STK_NOSYNC);
  }
}

void get_version(uint8_t c) {
  switch (c) {
    case 0x80:
      breply(HWVER);
      break;
    case 0x81:
      breply(SWMAJ);
      break;
    case 0x82:
      breply(SWMIN);
      break;
    case 0x93:
      breply('S'); // serial programmer
      break;
    default:
      breply(0);
  }
}

void set_parameters() {
  // call this after reading parameter packet into buff[]
  param.devicecode = buff[0];
  param.revision   = buff[1];
  param.progtype   = buff[2];
  param.parmode    = buff[3];
  param.polling    = buff[4];
  param.selftimed  = buff[5];
  param.lockbytes  = buff[6];
  param.fusebytes  = buff[7];
  param.flashpoll  = buff[8];
  // ignore buff[9] (= buff[8])
  // following are 16 bits (big endian)
  param.eeprompoll = beget16(&buff[10]);
  param.pagesize   = beget16(&buff[12]);
  param.eepromsize = beget16(&buff[14]);

  // 32 bits flashsize (big endian)
  param.flashsize = buff[16] * 0x01000000
                    + buff[17] * 0x00010000
                    + buff[18] * 0x00000100
                    + buff[19];

  // AVR devices have active low reset, AT89Sx are active high
  rst_active_high = (param.devicecode >= 0xe0);
}

void start_pmode() {

  // Reset target before driving PIN_SCK or PIN_MOSI

  // SPI.begin() will configure SS as output, so SPI master mode is selected.
  // We have defined RESET as pin 10, which for many Arduinos is not the SS pin.
  // So we have to configure RESET as output here,
  // (reset_target() first sets the correct level)
  reset_target(true);
  pinMode(RESET, OUTPUT);
  SPI.begin();
  SPI.beginTransaction(SPISettings(SPI_CLOCK, MSBFIRST, SPI_MODE0));

  // See AVR datasheets, chapter "SERIAL_PRG Programming Algorithm":

  // Pulse RESET after PIN_SCK is low:
  digitalWrite(PIN_SCK, LOW);
  delay(20); // discharge PIN_SCK, value arbitrarily chosen
  reset_target(false);
  // Pulse must be minimum 2 target CPU clock cycles so 100 usec is ok for CPU
  // speeds above 20 KHz
  delayMicroseconds(100);
  reset_target(true);

  // Send the enable programming command:
  delay(50); // datasheet: must be > 20 msec
  spi_transaction(0xAC, 0x53, 0x00, 0x00);
  pmode = 1;
}

void end_pmode() {
  SPI.end();
  // We're about to take the target out of reset so configure SPI pins as input
  pinMode(PIN_MOSI, INPUT);
  pinMode(PIN_SCK, INPUT);
  reset_target(false);
  pinMode(RESET, INPUT);
  pmode = 0;
}

void universal() {
  uint8_t ch;

  fill(4);
  ch = spi_transaction(buff[0], buff[1], buff[2], buff[3]);
  breply(ch);
}

void flash(uint8_t hilo, unsigned int addr, uint8_t data) {
  spi_transaction(0x40 + 8 * hilo,
                  addr >> 8 & 0xFF,
                  addr & 0xFF,
                  data);
}
void commit(unsigned int addr) {
  if (PROG_FLICKER) {
    prog_lamp(LOW);
  }
  spi_transaction(0x4C, (addr >> 8) & 0xFF, addr & 0xFF, 0);
  if (PROG_FLICKER) {
    delay(PTIME);
    prog_lamp(HIGH);
  }
}

unsigned int current_page() {
  if (param.pagesize == 32) {
    return here & 0xFFFFFFF0;
  }
  if (param.pagesize == 64) {
    return here & 0xFFFFFFE0;
  }
  if (param.pagesize == 128) {
    return here & 0xFFFFFFC0;
  }
  if (param.pagesize == 256) {
    return here & 0xFFFFFF80;
  }
  return here;
}


void write_flash(int length) {
  fill(length);
  if (CRC_EOP == getch()) {
    SERIAL.print((char) STK_INSYNC);
    SERIAL.print((char) write_flash_pages(length));
  } else {
    ISPError++;
    SERIAL.print((char) STK_NOSYNC);
  }
}

uint8_t write_flash_pages(int length) {
  int x = 0;
  unsigned int page = current_page();
  while (x < length) {
    if (page != current_page()) {
      commit(page);
      page = current_page();
    }
    flash(LOW, here, buff[x++]);
    flash(HIGH, here, buff[x++]);
    here++;
  }

  commit(page);

  return STK_OK;
}

#define EECHUNK (32)
uint8_t write_eeprom(unsigned int length) {
  // here is a word address, get the byte address
  unsigned int start = here * 2;
  unsigned int remaining = length;
  if (length > param.eepromsize) {
    ISPError++;
    return STK_FAILED;
  }
  while (remaining > EECHUNK) {
    write_eeprom_chunk(start, EECHUNK);
    start += EECHUNK;
    remaining -= EECHUNK;
  }
  write_eeprom_chunk(start, remaining);
  return STK_OK;
}
// write (length) bytes, (start) is a byte address
uint8_t write_eeprom_chunk(unsigned int start, unsigned int length) {
  // this writes byte-by-byte, page writing may be faster (4 bytes at a time)
  fill(length);
  prog_lamp(LOW);
  for (unsigned int x = 0; x < length; x++) {
    unsigned int addr = start + x;
    spi_transaction(0xC0, (addr >> 8) & 0xFF, addr & 0xFF, buff[x]);
    delay(45);
  }
  prog_lamp(HIGH);
  return STK_OK;
}

void program_page() {
  char result = (char) STK_FAILED;
  unsigned int length = 256 * getch();
  length += getch();
  char memtype = getch();
  // flash memory @here, (length) bytes
  if (memtype == 'F') {
    write_flash(length);
    return;
  }
  if (memtype == 'E') {
    result = (char)write_eeprom(length);
    if (CRC_EOP == getch()) {
      SERIAL.print((char) STK_INSYNC);
      SERIAL.print(result);
    } else {
      ISPError++;
      SERIAL.print((char) STK_NOSYNC);
    }
    return;
  }
  SERIAL.print((char)STK_FAILED);
  return;
}

uint8_t flash_read(uint8_t hilo, unsigned int addr) {
  return spi_transaction(0x20 + hilo * 8,
                         (addr >> 8) & 0xFF,
                         addr & 0xFF,
                         0);
}

char flash_read_page(int length) {
  for (int x = 0; x < length; x += 2) {
    uint8_t low = flash_read(LOW, here);
    SERIAL.print((char) low);
    uint8_t high = flash_read(HIGH, here);
    SERIAL.print((char) high);
    here++;
  }
  return STK_OK;
}

char eeprom_read_page(int length) {
  // here again we have a word address
  int start = here * 2;
  for (int x = 0; x < length; x++) {
    int addr = start + x;
    uint8_t ee = spi_transaction(0xA0, (addr >> 8) & 0xFF, addr & 0xFF, 0xFF);
    SERIAL.print((char) ee);
  }
  return STK_OK;
}

void read_page() {
  char result = (char)STK_FAILED;
  int length = 256 * getch();
  length += getch();
  char memtype = getch();
  if (CRC_EOP != getch()) {
    ISPError++;
    SERIAL.print((char) STK_NOSYNC);
    return;
  }
  SERIAL.print((char) STK_INSYNC);
  if (memtype == 'F') {
    result = flash_read_page(length);
  }
  if (memtype == 'E') {
    result = eeprom_read_page(length);
  }
  SERIAL.print(result);
}

void read_signature() {
  if (CRC_EOP != getch()) {
    ISPError++;
    SERIAL.print((char) STK_NOSYNC);
    return;
  }
  SERIAL.print((char) STK_INSYNC);
  uint8_t high = spi_transaction(0x30, 0x00, 0x00, 0x00);
  SERIAL.print((char) high);
  uint8_t middle = spi_transaction(0x30, 0x00, 0x01, 0x00);
  SERIAL.print((char) middle);
  uint8_t low = spi_transaction(0x30, 0x00, 0x02, 0x00);
  SERIAL.print((char) low);
  SERIAL.print((char) STK_OK);
}
//////////////////////////////////////////
//////////////////////////////////////////


////////////////////////////////////
////////////////////////////////////
void avrisp() {
  uint8_t ch = getch();
  switch (ch) {
    case '0': // signon
      ISPError = 0;
      empty_reply();
      break;
    case '1':
      if (getch() == CRC_EOP) {
        SERIAL.print((char) STK_INSYNC);
        SERIAL.print("AVR ISP");
        SERIAL.print((char) STK_OK);
      } else {
        ISPError++;
        SERIAL.print((char) STK_NOSYNC);
      }
      break;
    case 'A':
      get_version(getch());
      break;
    case 'B':
      fill(20);
      set_parameters();
      empty_reply();
      break;
    case 'E': // extended parameters - ignore for now
      fill(5);
      empty_reply();
      break;
    case 'P':
      if (!pmode) {
        start_pmode();
      }
      empty_reply();
      break;
    case 'U': // set address (word)
      here = getch();
      here += 256 * getch();
      empty_reply();
      break;

    case 0x60: //STK_PROG_FLASH
      getch(); // low addr
      getch(); // high addr
      empty_reply();
      break;
    case 0x61: //STK_PROG_DATA
      getch(); // data
      empty_reply();
      break;

    case 0x64: //STK_PROG_PAGE
      program_page();
      break;

    case 0x74: //STK_READ_PAGE 't'
      read_page();
      break;

    case 'V': //0x56
      universal();
      break;
    case 'Q': //0x51
      ISPError = 0;
      end_pmode();
      empty_reply();
      break;

    case 0x75: //STK_READ_SIGN 'u'
      read_signature();
      break;

    // expecting a command, not CRC_EOP
    // this is how we can get back in sync
    case CRC_EOP:
      ISPError++;
      SERIAL.print((char) STK_NOSYNC);
      break;

    // anything else we will return STK_UNKNOWN
    default:
      ISPError++;
      if (CRC_EOP == getch()) {
        SERIAL.print((char)STK_UNKNOWN);
      } else {
        SERIAL.print((char)STK_NOSYNC);
      }
  }
}

Compared mine with yours, we are using the same sketch.

The old one:

The (comparatively) new one:

Both:

The old one has an AU IC, the new one has a U-PH. First time I see a U-PH marking on a 328.