uint8_t
modbus_rxstart(uint8_t *data, uint8_t len, int16_t *recv_len) {
#ifdef MODBUS_CLIENT_SUPPORT
if (data[0] == MODBUS_ADDRESS || data[0] == MODBUS_BROADCAST) {
modbus_client_process(data, len, recv_len);
if (data[0] == MODBUS_ADDRESS)
return 1;
}
#endif
if (modbus_data.crc_len != 0) return 0; /* There is an packet on the way */
/* enable the transmitter */
PIN_SET(MODBUS_TX);
modbus_recv_len_ptr = recv_len;
modbus_data.crc = modbus_crc_calc(data, len);
modbus_data.crc_len = 2;
modbus_data.data = data;
modbus_data.len = len;
/* Enable the tx interrupt and send the first character */
modbus_data.sent = 1;
usart(UCSR,B) |= _BV(usart(TXCIE));
usart(UDR) = data[0];
return 1;
}
void
modbus_periodic(void)
{
if (modbus_recv_timer == 0) return;
modbus_recv_timer--;
if (!modbus_recv_len_ptr) {
#ifdef MODBUS_CLIENT_SUPPORT
if (modbus_recv_timer == 0) {
/* check the crc */
uint16_t crc = modbus_crc_calc(modbus_client_state.data, modbus_client_state.len - 2);
uint16_t crc_recv =
((modbus_client_state.data[modbus_client_state.len - 1]) << 8)
| modbus_client_state.data[modbus_client_state.len - 2];
if (crc != crc_recv) {
modbus_client_state.len = 0;
return;
}
/* See if we are the receiver */
if (!(modbus_client_state.data[0] == MODBUS_ADDRESS
|| modbus_client_state.data[0] == MODBUS_BROADCAST))
return;
modbus_client_state.len -= 2;
/* A message for our own modbus stack */
int16_t recv_len;
modbus_client_process(modbus_client_state.data, modbus_client_state.len,
&recv_len);
if (recv_len) {
PIN_SET(MODBUS_TX);
modbus_data.data = modbus_client_state.data;
modbus_data.len = recv_len;
/* Enable the tx interrupt and send the first character */
modbus_data.sent = 1;
usart(UCSR,B) |= _BV(usart(TXCIE));
usart(UDR) = modbus_client_state.data[0];
}
modbus_client_state.len = 0;
}
#endif
return;
}
if (modbus_recv_timer != 0) return;
*modbus_recv_len_ptr = modbus_data.len;
if (*modbus_recv_len_ptr < 2)
*modbus_recv_len_ptr = -1;
if (modbus_data.data[0] != modbus_last_address) {
*modbus_recv_len_ptr = -1;
}
modbus_recv_len_ptr = NULL;
}