JUMA-TRX2 SPI bus signals
OH2NLT 29.10.2007
SPI serial bus is used in JUMA-TRX2 transceiver to transport several digital outputs from DDS/control board to the main board and to the all band filter board. Totally 16 bits are transmitted via SPI bus. Eight bits are used in the main board. IC6 74HC595 shift register / latch is used to receive and drive main board control signals. If all band RF filter board is present there is another 74HC595 shift register for the filter board control signals. See schematics and functional description for actual control output usage. JUMA-TRX2 SPI bus is active only when some output state changes. This way SPI bus generated interference can be minimized. Changing MODE or tuning very fast across whole coverage is the easiest way to generate SPI traffic for bus measurement purpose. Another way to generate continuous SPI traffic is via test commands. Set TRX-2 serial -mode to test (RS232=Test). Give command c (lower case c) from terminal. Response to the terminal should be:
SPI Tx cont. Test can be interrupted with any key.Some typical SPI bus waveforms for reference purpose.
Trace A = SPI bus latch-signal (SPI_LATCH), DDS board J2-11
Trace B = SPI bus clock signal (SPI_CLK),, DDS board J2-8
Trace A = detail view of the 1,46us wide SPI_LATCH signal. It is rather difficult to see without memory oscilloscope
.
Trace A = SPI bus latch signal (SPI_LATCH), DDS board J2-11
Trace B = SPI bus data signal (SPI_SDO), DDS board J2-6
Trace A = SPI bus clock signal (SPI_CLK), DDS board J2-8
Trace B = SPI bus data signal (SPI_SDO),, DDS board J2-6
Note: Clock signal is filtered and inverted in the main board (IC7 and R95/C91) and in the RF filter board (IC3 and R8/C46). If you are doing fault finding clock signal should be checked also from 74HC595 pin # 11.
Example of bad SPI_CLK signal. Wrong (too high) value of capacitor C91.
Trace A = SPI bus clock signal (SPI_CLK), main board IC7-2
Trace B = main board IC7-4, no signal
Example of good SPI_CLK signal.
Trace A = SPI bus clock signal (SPI_CLK), main board IC7-2
Trace B = SPI bus clock signal (SPI_CLK), main board IC7-4 / IC6-11