[英]Converting struct to pointer of member type
Hi I'm a student Electronics-ICT and I'm having some trouble with a I2C project. 嗨,我是一名学生,电子信息通讯技术,我在I2C项目中遇到了一些麻烦。 I'm using FreeRTOS as a scheduler. 我正在使用FreeRTOS作为调度程序。 To pass data between tasks I use the BaseType_t xQueueSend(QueueHandle_t xQueue, const void *pvItemToQueue, TickType_t xTicksToWait);
为了在任务之间传递数据,我使用了BaseType_t xQueueSend(QueueHandle_t xQueue, const void *pvItemToQueue, TickType_t xTicksToWait);
method that requires a item (in my case a struct). 需要一个项目(在我的例子中是一个结构)的方法。 I have 3 struct types, 1 is the mainframe that has a payload field, the second one is a payload request (C-APDU format) and the last struct is a respond payload (R-APDU format). 我有3种结构类型,1种是具有有效负载字段的大型机,第二种是有效负载请求(C-APDU格式),最后一个结构是响应有效负载(R-APDU格式)。
Below a example of my structs. 下面是我的结构示例。
// mainframe I2C
typedef struct I2CMainFrame
{
//RF or I2C host to M24SR64-Y:
//C-APDU M24SR64-Y to RF or I2C host: R-APDU
uint8_t DID;
uint8_t PCB; // PCB field
void *Payload; // Payload
uint8_t CRC1; // 2 CRC bytes
uint8_t CRC2;
} I2CMainFrame_t;
// payload request
typedef struct PayloadSend
{
uint8_t CLA; // Class byte 0x00: standard command 0xA2: ST comman
uint8_t INS; // Instruction byte
uint8_t P1; // Param Byte 1
uint8_t P2; // Param Byte 2
uint8_t LC; // Number of bytes of the Data field
uint8_t *Data; // Data bytes
uint8_t Le; // Number of bytes to be read in the M24SR64-Y memory
} PayloadSend_t;
// payload response
typedef struct PayloadGet
{
uint8_t *Data; // Pointer to data
uint8_t SW1; // status byte 1
uint8_t SW2; // status byte 2
} PayloadGet_t;
The problem is when i want to acces the data. 问题是当我想访问数据时。 I need to pass a pointer to a methode that writes the data byte by byte on the I2C bus or that can calculate the CRC value for example: 我需要传递一个指向方法的指针,该方法在I2C总线上逐字节写入数据或可以计算CRC值,例如:
void CalculateCRC(uint8_t *data, size_t szLen, uint8_t *outputBuffer);
void WriteDataOnI2CBus(uint8_t *data, size_t szLen);
Is it posible to do something like this? 做这样的事情可行吗? I Tried the following code: 我尝试了以下代码:
I2CMainFrame_t mainframe;
PayloadSend_t payload;
void rtosUartTask(void)
{
//Fill payloaddata
uint8 data[] = {0xD2, 0x76, 0x00, 0x00, 0x85, 0x01, 0x01};
payload.CLA = 0x00; payload.INS = 0xA4; payload.P1 = 0x04;
payload.P2 = 0x00; payload.LC = 0x07;
payload.Data = data; payload.Le = 0x00;
//fill mainframe data
mainframe.DID = 0xAC; mainframe.PCB = 0x02;
mainframe.Payload = &payload;
//methode for passing struct to I2C task
xQueueSend(I2CQueue, &mainframe,0);
}
I2CMainFrame_t mainframe;
void rtosUartTask(void)
{
//Task manager starts this method when there is a item in the queue
xQueueReceive(I2CQueue, &mainframe, portMAX_DELAY);
//This doesnt work
uint8_t *pointerToStructMembers = &mainframe;
WriteDataOnI2CBus(pointerToStructMembers, sizeof(mainframe));
}
Am I looking in the right direction here or should I try another approach? 我在这里寻找正确的方向还是应该尝试其他方法?
uint8_t *pointerToStructMembers = &mainframe;
You cannot use typecast since I2CMainFrame
contains pointer member void *Payload
. 您不能使用类型转换,因为I2CMainFrame
包含指针成员void *Payload
。
What you can try is serialize the mainframe
as below. 您可以尝试按以下步骤序列化mainframe
。
Declare an array of uint8_t
then individually copy the contents to it. 声明一个uint8_t
数组,然后将内容单独复制到其中。
uint8_t bufferedStructMembers[sizeof(I2CMainFrame_t) + sizeof (PayloadSend_t) + ((PayloadSend_t *)(mainframe.Payload))->LC];
bufferedStructMembers[0] = mainframe.DID;
bufferedStructMembers[1] = mainframe.PCB;
bufferedStructMembers[2] = ((PayloadSend_t *)(mainframe.Payload))->CLA;
bufferedStructMembers[3] = ((PayloadSend_t *)(mainframe.Payload))->INS;
bufferedStructMembers[4] = ((PayloadSend_t *)(mainframe.Payload))->P1;
bufferedStructMembers[5] = ((PayloadSend_t *)(mainframe.Payload))->P2;
bufferedStructMembers[6] = ((PayloadSend_t *)(mainframe.Payload))->LC;
memcpy(&bufferedStructMembers[7], ((PayloadSend_t *)(mainframe.Payload))->Data, ((PayloadSend_t *)(mainframe.Payload))->LC);
bufferedStructMembers[((PayloadSend_t *)(mainframe.Payload))->LC+7] = mainframe.Le;
bufferedStructMembers[((PayloadSend_t *)(mainframe.Payload))->LC+8] = mainframe.CRC1; // 2 CRC bytes
bufferedStructMembers[((PayloadSend_t *)(mainframe.Payload))->LC+9] = mainframe.CRC2;
WriteDataOnI2CBus(bufferedStructMembers, sizeof(mainframe));
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