good morning,
We are manufacturing a reader based on the circuit of the application note of trf7970, the only change lies in the Uc.
After manufacturing the first 2000u we had a failure rate of 20%. So far we have not found the problem since in all cases the problem is the same.
The reader only identifies the tag if it is practically supported on the antenna, whereas in the pcb that works correctly this can be realized from the 70mm inclusively.
Design and component problems were ruled out because measurements and component changes were performed without results.
Doing analysis of the firmware and debuger note that in those that present faults also detect the tags at 70mm but always with error CRC (error CRC in RX) causing the routine to be abruptly terminated and can not be used.
Following with the tests I was able to initialize using the RX_2 as main receiver and the result was that the tags were correctly read.
This leads me to ask how can I do a firmware routine to decide whether to use the RX_1 or RX_2 antenna?
I am working with the commands "test internal rssi" "text external rssi" but it returns me values I do not think are correct.
// Example routine
/ * Test_Internal_RF * /
// DirectCommand (Trf_enable_receivers)
// Set B5 of the chip status control
// Set B1 of the Chip status control
// DirectCommand (0x18)
// Read Rssi register
Value = "85" which means Rssi Rx2 = 2
Rx1 = 5
In the case of the External Test
Value = "71" meaning Rssi Rx2 = 0 ???
Rx1 = 7 ??
I hope I did not stun them with the story but we took a couple of weeks with these problems and this was the summary.
Do not clarify but we are working with ISO-15693 and ICODE tags.
I hope you can help me.
regards