Bugs live forever if we don't kill them.
When programming low frequency RC clocked MCU's, ArduinoISP's low speed SPI class BitBangedSPI has very poor timing.
It can be fixed like this:
line 200 (Arduino 1.6.9~1.8.2)
original:
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;
}
fixed:
uint8_t transfer (uint8_t b) {
for (unsigned int i = 0; i < 8; ++i) {
digitalWrite(PIN_MOSI, (b & 0x80) ? HIGH : LOW);
delayMicroseconds(pulseWidth);
digitalWrite(PIN_SCK, HIGH);
b = (b << 1) | digitalRead(PIN_MISO);
delayMicroseconds(pulseWidth);
digitalWrite(PIN_SCK, LOW); // slow pulse
}
return b;
}