I2C: Fix bug with command 0x00 always returning zero

common/src/i2c_slave.c

@@ -17,7 +17,7 @@ static struct io_descriptor *io;
 static uint16_t dev_addr __xMR;
 static uint16_t rx_state __xMR = CMD;
 static uint8_t tmp_std_cmd_addr;
-static uint16_t std_cmd_addr __xMR;
+static uint16_t std_cmd_addr __xMR = 0xFF;
 static int16_t cmd_index __xMR;
 static int16_t cmd_len __xMR;
 static uint8_t tmp_ext_cmd_addr;
@@ -72,7 +72,6 @@ static void __xMR I2C_rx_complete(const struct i2c_s_async_descriptor *const des
                 if (use_pec)
                         pec_checksum = crc8_byte(pec_checksum ^ std_cmd_addr);
                 if (std_cmd_addr == 0xFF) {
-                        std_cmd_addr = 0;
                         rx_state = EXT_CMD;
                         send_ack(descr);
                         set_cmd(descr, 3);
@@ -223,7 +222,7 @@ static void __xMR I2C_tx_pending(const struct i2c_s_async_descriptor *const desc
                 added_tx_pec = 1;
                 sent_checksum = 0;
         }
-        if (std_cmd_addr) {
+        if (std_cmd_addr != 0xFF) {
                 if ((*cmds->cmds[cmd_index].data_len < 0) && (!blk_wrote_len_byte)) {
                         cmd_len = 0;
                         tx_tmp = -*cmds->cmds[cmd_index].data_len;