TRF7964A: 15693协议，标签芯片已经返回数据，但是FIFO里面没有数据

Hi Wenwu,

can you please repeat your question in English.

Best Regards,

Helfried

trf7964A work in iso15693, when the ic tx cmd(260100), the tag response the cmd , and i can see the subcarrier signal at pin12, but the fifo len is zero in fifo status reg, the irq status reg don't have the error flags. 

Hi Wenwu,

are you resetting the FIFO after receiving the TX interrupt as described in the FAQ chapter 4.6:

https://www.ti.com/lit/pdf/sloa248

What is the command you are sending? It is not clear for me what ISO command 260100 is.

Best Regards,

Helfried

hi !

this is my c code.

while(tick < waitTime)   //wait timeout
    {
        if(Trf796x_GetIrqState())   //get the irq pin status
        {
            flag = Trf796x_ReadReg(TRF796X_REG_IRQ_STATUS);  //read irq reg
            if(flag & TRF796X_REG_ERR_MSK)                     //if the reg value is error code, stop receive the tag rsp.
            {
                err = Trf796x_FmtErrInfo(flag & TRF796X_REG_ERR_MSK);
                break;
            }
            else if(flag & TRF796X_REG_IRQ_TX_END)             //if the reg value is tx end, cleat the fifo
            {
                Trf796x_WriteCmd(TRF796X_CMD_RESET_FIFO);   //清空FIFO
            }
            else if(flag & TRF796X_REG_IRQ_FIFO_LV)          //
            {
                err = Trf796x_FmtErrInfo(flag & TRF796X_REG_ERR_MSK);
            }
            else
            {
                if(flag & TRF796X_REG_IRQ_RX_START) //if the reg value, read the tag rsp.
                {
                    err = TRF796X_ERR_OK;
                    err = Trf796x_ReadReg(TRF796X_REG_IRQ_STATUS);
                    rxFifoLen = Trf796x_ReadReg(TRF796X_REG_FIFO_CONTROL) & TRF796X_REG_FIFO_RXLEN_MSK;
                    Trf796x_ReadRegs(TRF796X_REG_FIFO, rxFifoLen, pTrf76xFrame->frame + pTrf76xFrame->rxLen);
                    pTrf76xFrame->rxLen = rxFifoLen;
                    break;
                }
            }
        }
        tick++;
    }

the bug is: the tag in the ant, the tag respons the cmd(260100---15693 inventory one tag),   trf7964a can read the RX_START flag, but the fifo length is zero.

the bug doesn't appear every time.

Hi,

as far as I can see the code looks good. The only thing that makes we wonder is that the code runs in a loop and is not setup as an interrupt service routine. Because resetting the FIFO should be done immediate after the TX ready IRQ this is maybe not fast enough in your case.

Best Regards,

Helfried 

The spi speed is 9Mhz, it is very fast.

The cpu speed is 72Mhz.

I think the loop is fast enough, and when cpu receive the tx end flag, the trf7964 must wait 330us receive the tag response sof signal.

when the fifo length is zero, the subcarrier signal at pin12 is very good.But, why the trf7964 don,t have tag rsp in the fifo?

sometime, the trf7964 work very good, it can receive the correct tag rsp, and other time ,the trf7964 is not so good .

why?

the trf7964 regs:

addr------------value

00----------------20

01----------------02

02----------------00

03----------------00

04----------------c1

05----------------bb

06----------------00

07----------------14

08----------------18

09----------------09

0a----------------4c

0b----------------06

0c----------------00

0d----------------1f

0e----------------00

0f----------------40

10----------------10

.----------------00

.----------------00

.----------------00

Hi,

You are working with a very fast SPI clock and fast CPU speed. I have checked in the forum if I could find a similar problem and came across a post where the customer needed to insert a delay between detecting the RX start IRQ and checking the FIFO. This was necessary because the RX IRQ signaling the SOF was received not that RX is finished. Maybe this makes a difference.

Best Regards,

Helfried

Hi,

I haven’t heard back from you for a while, so this tread is being closed. If you wish to continue the discussion, please post a reply with an update below (or create a new thread).

Best Regards,
Helfried