{"id":211,"date":"2019-05-16T00:48:33","date_gmt":"2019-05-15T19:18:33","guid":{"rendered":"https:\/\/tangentmotorsport.com\/?p=211"},"modified":"2019-05-16T00:54:56","modified_gmt":"2019-05-15T19:24:56","slug":"eeprom-fun","status":"publish","type":"post","link":"https:\/\/blogs.tangentmotorsport.com\/?p=211","title":{"rendered":"EEPROM fun"},"content":{"rendered":"\n

I had to program a legacy EEPROM on a Mercedes EDC15 ECU. I had a choice: to buy a reliable tool to read\/write the E2P(3SP08\/95SP08) or make my own by reading the datasheet. I chose the 2nd option.<\/p>\n\n\n\n\n\n\n\n

This particular E2P isn’t supported by any opensource libraries(it’s very old), so the first thing I had to figure out was how the SPI was to be configured. Data\/instructions are sent MSB first. Clock is low when idle and data is sampled on leading edge of clock. This means it’s Mode 0 SPI(CPOL = 0, CPHA = 0). This E2P had a max SPI clock of 2MHz, to be safe I used the slowest clock mode on arduino:<\/p>\n\n\n\n

SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR1)|(1<<SPR0);<\/p>\n\n\n\n

The opcodes for the instructions were special on this E2P: <\/p>\n\n\n\n<\/a>\n\n\n\n

The 2 MSb’s of the address(A9, A8) were to be encoded with the READ\/WRITE opcode. I wrote these functions for R\/W of this E2P on arduino:<\/p>\n\n\n\n

byte read_eeprom(int EEPROM_address)
\n{
\n  \/\/READ EEPROM
\n  int data;
\n  digitalWrite(SLAVESELECT,LOW);
\n  \/\/ bit A8 and A9 are copied to bit pos 4 and 5 of READ\/WRITE opcode
\n  byte A8A9=(byte)((EEPROM_address & 0x300) >> 5);
\n  spi_transfer(READ | A8A9); \/\/transmit read opcode
\n  spi_transfer((byte)(EEPROM_address));      \/\/send LSByte address
\n  data = spi_transfer(0xFF); \/\/get data byte
\n  digitalWrite(SLAVESELECT,HIGH); \/\/release chip, signal end transfer
\n  return data;
\n}<\/pre>\n\n\n\n
void write_eeprom(int EEPROM_address, char data)
\n{
\n  \/\/WRITE EEPROM
\n  digitalWrite(SLAVESELECT,LOW);
\n  spi_transfer(WREN);
\n  digitalWrite(SLAVESELECT,HIGH);
\n  delay(5);
\n  digitalWrite(SLAVESELECT,LOW);
\n  \/\/ bit A8 and A9 are copied to bit pos 4 and 5 of READ\/WRITE opcode
\n  byte A8A9=(byte)((EEPROM_address & 0x300) >> 5);
\n  spi_transfer(WRITE | A8A9); \/\/transmit read opcode
\n  spi_transfer((byte)(EEPROM_address));      \/\/send LSByte address
\n  spi_transfer(data); \/\/write data byte
\n  digitalWrite(SLAVESELECT,HIGH); \/\/release chip, signal end transfer
\n  delay(5);
\n}<\/pre>\n\n\n\n
The delays in the write function are to follow the timing diagrams in the datasheet:<\/p>\n\n\n\n<\/a>\n\n\n\n
I was in a rush to test this out, here’s the wiring:<\/p>\n\n\n\n<\/a>\n\n\n\n
Now, I’ll be testing an Immobiliser delete for this engine(never been made before by anyone \ud83d\ude09 ), lying in my backyard:<\/p>\n\n\n\n<\/a>\n\n\n\n
<\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"
I had to program a legacy EEPROM on a Mercedes EDC15 ECU. I had a choice: to buy a reliable tool to read\/write the E2P(3SP08\/95SP08) or make my own by reading the datasheet. 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