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Reset target before driving SCK or MOSI, reset sequence as in AVR datasheets under "Serial Programming Algorithm"

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This commit is contained in:
Peter Van Hoyweghen 2015-08-26 22:43:00 +02:00
parent 044a7b78c7
commit 13cc57ed7e
1 changed files with 22 additions and 11 deletions
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33
build/shared/examples/11.ArduinoISP/ArduinoISP/ArduinoISP.ino
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@ -169,7 +169,6 @@ static BitBangedSPI SPI;
void setup() {
SERIAL.begin(19200);
pinMode(LED_PMODE, OUTPUT);
pulse(LED_PMODE, 2);
pinMode(LED_ERR, OUTPUT);
@ -348,21 +347,33 @@ void set_parameters() {
}
void start_pmode() {
SPI.begin();
SPI.beginTransaction(SPISettings(SPI_CLOCK, MSBFIRST, SPI_MODE0));
// SPI.begin() has configured SS as output,
// Reset target before driving SCK or MOSI
// SPI.begin() will configure SS as output,
// so SPI master mode is selected.
// We have defined RESET as pin 10,
// which for many arduino's is not the SS pin.
// So we have to configure RESET as output here,
// (reset_target() first sets the level correct)
reset_target(false);
pinMode(RESET, OUTPUT);
digitalWrite(SCK, LOW);
delay(20);
// (reset_target() first sets the correct level)
reset_target(true);
delay(50);
pinMode(RESET, OUTPUT);
SPI.begin();
SPI.beginTransaction(SPISettings(SPI_CLOCK, MSBFIRST, SPI_MODE0));
// See avr datasheets, chapter "SERIAL_PRG Programming Algorithm":
// Pulse RESET after SCK is low:
digitalWrite(SCK, LOW);
delay(20); // discharge SCK, value arbitrally chosen
reset_target(false);
// Pulse must be minimum 2 target CPU clock cycles
// so 100 usec is ok for CPU speeds above 20KHz
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;
}