RDS CODER PIRA MRDS1322 |
After evaluating various free RDS coders (encoders) available on dedicated forums, it became evident that most exhibited notable limitations. Common issues included malfunctioning Dynamic PS, occasional glitches causing system lock-ups, poor spectral purity due to basic D/A conversion methods, and the inability to synchronize with the 19 kHz pilot signal. These shortcomings led to the decision to replicate an RDS encoder using a pre-programmed microcontroller (commercially available) from PIRA.CZ.
The MRDS1322 RDS coder was selected as a starting point, utilizing a PIC18F13K22 microcontroller. The design process was guided by documentation available on the PIRA.CZ website, the official MRDS datasheet, and the MicroRDS Encoder reference design.
Several modifications were implemented in the final build. A USB/UART interface was added using an FTDI FT232 chip. The original LC output filter was replaced with a 57 kHz active band-pass filter, modeled after the one found in the Inovonics 720. A differential power supply (AC or DC) was used, sourced from the existing stereo coder located within the same enclosure.
Configuration of the MRDS coder was carried out using the TinyRDS software. Operation proved to be stable, with excellent results.
The "MRDS1322" microcontroller is available through the PIRA online shop (Online Shop → RDS Encoders - Components) at a cost of approximately €12 plus shipping. The PCB layout was designed for the DIP-20 version of the chip.
A 4.332 MHz quartz crystal is required and can be sourced from the PIRA.CZ shop, suppliers such as Mouser, or salvaged from older car radio.
Note: The MRDS RDS coder, including firmware and PC software, is the intellectual property of PIRA.CZ. The contribution focused solely on incorporating the microcontroller into the custom PCB.
MRDS1322 RDS Coder schematic
MRDS1322 RDS Coder PCB v1 (gerber)
PCB top view
PCB bottom view
TinyRDS PC software (link)
TinyRDS Guide (link)
MRDS1322 datasheet (link)
MicroRDS Encoder user manual (link)
