FIFO on CLRC632

jbertrand — Thu, 18 Mar 2021 20:58:53 GMT

Hello,

I'm trying to write some functions to read ISO14443a tag with a CLRC632. I have written several functions to read and write registers, to read and write fifo and I'm pretty sure these functions are bug free as I can send a frame to FIFO, compute CRC code and read this CRC code from FIFO (with of course expected value).

Now, I'm triying to transceive a short frame (REQA). My function doesn't work and I have added some traces.

uint8_t iso14443a_transceive_short_frame(uint8_t commande, iso14443a_atqa_t *atqa) { uint8_t longueur; char t[40]; sprintf(t, "%d ", clrc632_read_register(CmdFIFOLength)); // 7 bits, sans parité clrc632_write_register(CmdCommand, C_Idle); sprintf(t, "%s%d ", t, clrc632_read_register(CmdFIFOLength)); clrc632_write_register(RfChannelRedundancy, 0x00); sprintf(t, "%s%d ", t, clrc632_read_register(CmdFIFOLength)); clrc632_write_register(CtrlBitFraming, 7); sprintf(t, "%s%d ", t, clrc632_read_register(CmdFIFOLength)); memset(atqa, 0, sizeof(*atqa)); sprintf(t, "%s%d ", t, clrc632_read_register(CmdFIFOLength)); clrc632_write(CmdFIFOData, (uint8_t *) &commande, sizeof(commande)); sprintf(t, "%s%d ", t, clrc632_read_register(CmdFIFOLength)); clrc632_write_register(CmdCommand, C_Transceive); sprintf(t, "%s%d\n\r", t, clrc632_read_register(CmdFIFOLength)); vfd_send_byte(0x0C); vfd_print(t); longueur = 0; hz_set_t0(hz_timeout_nfc); do { if ((longueur = clrc632_read_register(CmdFIFOLength)) == 2) { break; } } while(hz_get_ts(hz_timeout_nfc) <= 5); if (longueur == 2) { (*atqa).data[0] = CmdFIFOData; (*atqa).data[1] = 0x00; clrc632_read((*atqa).data, longueur); sprintf(t, "%02X %02X", (*atqa).data[0], (*atqa).data[1]); vfd_print(t); } else { sprintf(t, "EL=%u", longueur); vfd_print(t); } clrc632_write_register(CmdCommand, C_Idle); return(ISO14443A_EXIT_SUCCESS); }

Of course, CRLC632 is initialized before this function. I have read datasheet and, for me, this code only pushs one byte in FIFO (0x26).

vfd_printf() prints informations on a VFD sreen and I can see :

0 0 1 1 1 2 1 EL=0

I don't understand why clrc632_write_register(RfChannelRedundancy, 0x00) writes a byte in FIFO. I have verified that RfChannelRedundancy value is 0x22. Please note that, after clrc632_write(CmdFIFOData, (uint8_t *) &commande, sizeof(commande)), another byte is written in FIFO (0x26).

I suppose I have misunderstood something. Explanation will be welcome.

Best regards,

Re: FIFO on CLRC632

jbertrand — Fri, 19 Mar 2021 09:04:48 GMT

If I wait for Idle command between write operations, CLRC632 works better. Now FIFO only contains one byte.

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