![]() ![]() ![]() The trade-off for very slow write times - traditionally - is that it's also non-volatile meaning that the data doesn't go away when power is removed from the device. This is because it's very slow - or impossible - to write new data to ROM. Read-Only Memory ( ROM) is a type of computer memory which, generally speaking, is only programmed once (or very occasionally) and then gets read from the rest of the time. That said, if you don't nerd-out on computer history it's probably safe to skip that section. ![]() Serial.Before we get into the hookup it's probably a good idea to familiarize ourselves with EEPROM and the history of ROM in general. Size_t actually_read = Wire.readBytes(buf, 4) Serial.printf("Register value: %08lx\r\n", _builtin_bswap32(buf)) įor an explanation on why we need _builtin_bswap32(), see How to print 32-bit uint32_t as eight hex digits in Arduino Option 2: Reading the register into an uint8_t array const uint8_t SLAVE_I2C_ADDRESS = 0b1010 Size_t actually_read = Wire.readBytes((uint8_t*)&buf, 4) Wire.requestFrom(SLAVE_I2C_ADDRESS, 4) // This register is 32 bits = 4 bytes longĭelay(5) // Wait for data to be available Wire.beginTransmission(SLAVE_I2C_ADDRESS) Option 1: Reading the register into an uint32_t (recommended) const uint8_t SLAVE_I2C_ADDRESS = 0b1010 Ĭonst uint16_t SLAVE_I2C_REGISTER_ADDRESS = 0x50 We will provide a full example with error handling in a followup post. This is a minimal example so it creates minimal confusion for the reader. Additionally, we wait for data using delay() instead of Wire.available(). Note that this code does not implement error handling for the sake of simplicity. In my opinion, it’s most efficient to just try out the standard way of reading a register and start from there. Note that some devices like the LAN9303 have a slightly different addressing scheme or other peculiarities. It will work with almost all I2C devices like EEPROMs, ADCs and others, provided you have the correct. The following code demonstrates how to read a register that is 4 bytes (32 bits) long over I2C. ![]()
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