Writing float to EEPROM

[VYoun]

Hello Guys,

I have a AT24CM02 EEPROM which uses I2C to communicate with a STM32H7 MCU.

I need to store some float values into the EEPROM, but I do not know how.

I appreciate any suggestions.

Thank you and best regards,

Vouria

[SKacp.1]

Hi,

Please see my functions to write and read data type float to memory FRAM FM24CL16

#define FRAM_HW_ADDRESS      0xA0
uint16_t addr;
float Memory_FL1;
 
void Read_Float (void)
{
addr = 0;
I2C_RP_F_FRAM(&addr, &Memory_FL1);
}
 
void Write_Float (void)
{
addr = 0;
I2C_WRP_F_FRAM(&addr, &Memory_FL1);
}
 
void I2C_WRP_F_FRAM (uint16_t *adress, float *pData_to_WR)
{
	uint16_t adr_temp = *adress;
 
	I2C_MEM_WB_FM24CL16(&adr_temp, *((uint8_t*)pData_to_WR));adr_temp++;
	I2C_MEM_WB_FM24CL16(&adr_temp, *((uint8_t*)pData_to_WR+1));adr_temp++;
	I2C_MEM_WB_FM24CL16(&adr_temp, *((uint8_t*)pData_to_WR+2));adr_temp++;
	I2C_MEM_WB_FM24CL16(&adr_temp, *((uint8_t*)pData_to_WR+3));
}
 
void I2C_RP_F_FRAM (uint16_t *adress, float *pData_to_R)
{
	uint16_t adr_temp = *adress;
 
	*((uint8_t*)pData_to_R) = I2C_MEM_RB_FM24CL16(&adr_temp);adr_temp++;
	*((uint8_t*)pData_to_R+1) = I2C_MEM_RB_FM24CL16(&adr_temp);adr_temp++;
	*((uint8_t*)pData_to_R+2) = I2C_MEM_RB_FM24CL16(&adr_temp);adr_temp++;
	*((uint8_t*)pData_to_R+3) = I2C_MEM_RB_FM24CL16(&adr_temp);
}
 
void I2C_MEM_WB_FM24CL16(uint16_t *WriteAddr, uint8_t WriteData)
{
	uint16_t Memadr;
	uint16_t Devadr;
 
	Memadr = *WriteAddr;
	Devadr = FRAM_HW_ADDRESS;
	COPY_BIT(Devadr, 1, Memadr, 8);
	COPY_BIT(Devadr, 2, Memadr, 9);
	COPY_BIT(Devadr, 3, Memadr, 10);
	Memadr = Memadr & 0x00FF;
	HAL_I2C_Mem_Write(&hi2c1, Devadr, Memadr, I2C_MEMADD_SIZE_8BIT, &WriteData, 1, 5);
}
 
uint8_t I2C_MEM_RB_FM24CL16(uint16_t *ReadAddr)
{
	uint16_t Memadr;
	uint16_t Devadr;
	uint8_t Readbyte;
 
	Memadr = *ReadAddr;
	Devadr = FRAM_HW_ADDRESS;
	COPY_BIT(Devadr, 1, Memadr, 8);
	COPY_BIT(Devadr, 2, Memadr, 9);
	COPY_BIT(Devadr, 3, Memadr, 10);
	Memadr = Memadr & 0x00FF;
	HAL_I2C_Mem_Read(&hi2c1, Devadr, Memadr, I2C_MEMADD_SIZE_8BIT, &Readbyte, 1, 5);
	/* Read a byte from the EEPROM */
	return (Readbyte);
}

[VYoun]

Thanks a lot for sharing, This is very useful, can you please clarify what "COPY_BIT" is doing?

[SKacp.1]

Hi,

#define COPY_BIT(t,tb,s,sb) t = s & (1<<(sb)) ? t | (1<<(tb)) : t & ~(1<<(tb))

[S.Ma · Accepted solution]

If you build a EEPROM write block which deals with EEPROM pages internally (not the case in F/M/RAM), it would be more generic

Then if you just save/retrieve data in EEPROM, use sizeof(my_variable) to get its size in bytes.

This way you can backup float, double, struct, anything without worry.

Please also note that EEPROM needs time after write a page or by polling the ACK bit of the EEPROM at the right time.

With a little extra effort in the early stage, the foundation will be more rugged.

[VYoun]

Thank you very much, I think this is the best way to do it.

[VYoun]

do you have any example code?