Name

modbus_write_bits - write many bits

Synopsis

int modbus_write_bits(modbus_t *ctx, int addr, int nb, const uint8_t *src);

Description

The modbus_write_bits() function shall write the status of the nb bits (coils) from src at the address addr of the remote device. The src array must contain bytes set to TRUE or FALSE.

The src array must be allocated with at least nb elements. It is the caller's responsibility to ensure the buffer is large enough to hold all the bits to be written.

The function uses the Modbus function code 0x0F (force multiple coils).

Return value

The function shall return the number of written bits if successful. Otherwise it shall return -1 and set errno.

Errors

• EINVAL, the ctx or src argument is NULL, or nb is less than 1.
• EMBMDATA, writing too many bits (nb > MODBUS_MAX_WRITE_BITS).

See also

• modbus_read_bits ⟨modbus_read_bits.md⟩
• modbus_write_bit ⟨modbus_write_bit.md⟩