spitsnsparkin
- Joined Jun 19, 2011
- 29
Hi rjjenkins,
I followed the previous links in the responses and watch the demonstration video. The read range is impressive, but likely due to the battery power supply. Noise greatly effects the quality of the read.
My project initially started with an off-the-shelf module which had the RFID reader IC and on-board MCU for decoding. The module's datasheet indicated that the “continuous read” mode consisted of back-to-back, discrete, 100ms frames. Each frame required two consecutive and error-free decodings of the tag id before it was output to the serial port. The on-board MCU decoded the tag id by watching the demodulated bit-stream for the “header” and then the following tag id data bits. If the tag's demodulated data was stable and the header was detected near the start of the frame, then it would likely succeed and output the tag id. However, if the header was detected toward the end, then the module would time-out the frame and start again. In my application, the module could not stream different tag ids at a fast enough rate, due to it's framed-sequential detection method. Using the HTRC1100 and Microchip MCU, I pipelined the acquisition and decoding processes. I used a clock-driven SPI interrupt to record the demodulated output of the HTRC1100 into a buffer. When enough bytes were captured for the received frame, the MCU would then search, align and decode the data bits (if present) in the buffer, while the SPI interrupt continued to acquire the next frame. Since you mentioned that you success rate was 98%, but random in error, it may be due to the MCU's acception/rejection policy as well as power supply noise quality.
As I'm an old-school assembly programmer, I'm half-tempted to order one of these modules and reverse-engineer the AFE, then reprogram the on-board MCU! On the module, I can see the discrete half-bridge driver and source originating from pin14 which also is passed to the MCU for synchronization. Likewise, the on-board resonant cap, filter and half-wave AM-envelope detector before I loose the signal is the tightly packed SMD caps and resistors beside the RFID chip.
Spitsnsparkin.
I followed the previous links in the responses and watch the demonstration video. The read range is impressive, but likely due to the battery power supply. Noise greatly effects the quality of the read.
My project initially started with an off-the-shelf module which had the RFID reader IC and on-board MCU for decoding. The module's datasheet indicated that the “continuous read” mode consisted of back-to-back, discrete, 100ms frames. Each frame required two consecutive and error-free decodings of the tag id before it was output to the serial port. The on-board MCU decoded the tag id by watching the demodulated bit-stream for the “header” and then the following tag id data bits. If the tag's demodulated data was stable and the header was detected near the start of the frame, then it would likely succeed and output the tag id. However, if the header was detected toward the end, then the module would time-out the frame and start again. In my application, the module could not stream different tag ids at a fast enough rate, due to it's framed-sequential detection method. Using the HTRC1100 and Microchip MCU, I pipelined the acquisition and decoding processes. I used a clock-driven SPI interrupt to record the demodulated output of the HTRC1100 into a buffer. When enough bytes were captured for the received frame, the MCU would then search, align and decode the data bits (if present) in the buffer, while the SPI interrupt continued to acquire the next frame. Since you mentioned that you success rate was 98%, but random in error, it may be due to the MCU's acception/rejection policy as well as power supply noise quality.
As I'm an old-school assembly programmer, I'm half-tempted to order one of these modules and reverse-engineer the AFE, then reprogram the on-board MCU! On the module, I can see the discrete half-bridge driver and source originating from pin14 which also is passed to the MCU for synchronization. Likewise, the on-board resonant cap, filter and half-wave AM-envelope detector before I loose the signal is the tightly packed SMD caps and resistors beside the RFID chip.
Spitsnsparkin.