Raspberry is I2C master and sends predefined packet to the slave: {0x06 0x08 0x04 0x00 0x02 0x10 0x0D}
MSP430G2553 receives and should send back an answer if the packet matches (first and last byte, 0x06 and 0x0D accordingly). I am able to save received bytes into array but if I try to send back the answer, then it sends: {0x06 0x04 0x02 0x10 0x06 0x04 0x02 0x10}. Basically it is skipping one byte after each and starts again from the beginning. Thee correct byte order should be as received order. I suspect that it is increasing the counter twice the speed as it should by calling out transmit_cb() but I don't understand why.
In short, how to send back received (and saved into array with slight modifications) data back to master from array?
Slave code:
#define P_SYNC 0x06
#define CTRL_REQ 0x08
#define CTRL_ANS 0x12
#define P_FOOTER 0x0D
/***************************************************************************************************
* Global Variable section *
***************************************************************************************************/
unsigned char flag = 0;
unsigned char flag1 = 0;
unsigned char TXData = 0;
unsigned char RXData = 0;
unsigned char in_array[64] = {0};
unsigned char save_flag = 0;
unsigned char counter = 0;
unsigned char txCount = 0;
/***************************************************************************************************
* Main *
***************************************************************************************************/
int main(void) {
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
TI_USCI_I2C_slaveinit(start_cb, transmit_cb, receive_cb, SLAVE_ADDR); // init the slave
_EINT();
BCSCTL1 = CALBC1_16MHZ;
DCOCTL = CALDCO_16MHZ;
LPM0; // Enter LPM0.
}
void start_cb() {
RXData = 0;
}
void receive_cb(unsigned char receive) {
//RXData = receive;
Save_Array(receive); // Save new data into array
RXData = Check_Bytes(receive); // Check packet header and footer
//flag1++;
}
void transmit_cb(unsigned char volatile *byte) {
//*byte = TXData;
if (txCount > 7)
txCount = 0;
TXData = in_array[txCount++];
*byte = TXData;
}
unsigned char Check_Bytes(unsigned char in_byte) {
switch (in_byte) {
case P_SYNC:
save_flag = 1; break;
case P_FOOTER:
/* TXData = P_FOOTER; */ break;
}
return TXData;
}
// *************************************************************************************************
// @fn Save_Array
// @brief Save received bytes into array
// @param uint8 in_byte Receiving byte
// @return None
// *************************************************************************************************
void Save_Array(unsigned char in_byte) {
// Reset counter if we find PACKET HEADER
if (in_byte == P_SYNC)
counter = 0;
// Replace REQUEST packet type with ANSWER
if ((in_byte == CTRL_REQ) && (counter == 1))
in_byte = CTRL_ANS;
in_array[counter] = in_byte; // Save new data into array
counter++; // Increase counter value
// If we see PACKET FOOTER then disable saving into array
if (in_byte == P_FOOTER)
save_flag = 0;
}
