ZX-1280 dev board pin description

[asalvi]

Hello all

I recently got a zx-1280 dev board and I'm trying to set up SPI communication with an analog devices iMEMS gyroscope. I found a drawing showing the schematic for the zx-1280 dev board with pin names but I can't find any specific pin description like the detailed pin description provided for the zx-24 in appendix B of the ZBasic Language Reference Manual.

Looking at the diagram I believe I need to use the pins 2 (SCK),3 (MOSI), and 4 (MISO) on Port B for SPI but I am not sure about what pin does the Chip Select.

Does anyone know where I can find a detailed pin description document?

Alex

[dkinzer]

Does anyone know where I can find a detailed pin description document?

On the Downloads page you'll find a link to download the full or summarized datasheet for the mega1281/mega1280. That Atmel document gives full and complete descriptions of the functions of each pin, operating specifications, etc.

It might be useful to print out the pinout diagram that can be found near the front of each datasheet. This will serve as a quick reminder of the pin number and/or port/bit assignment of many of the functions. For example, on that diagram for the mega1280 (reproduced below) you'll see that SCK is pin B.1 (pin 20) while MOSI and MISO are on B.2 and B.3 respectively. You can use any I/O pin for the chip select. One caveat is that when you use the SPI interface, you must not have SS (B.0) configured to be an input because that causes the AVR to try to operate in SPI slave mode instead of SPI master mode. For this reason, it is probably best to use B.0 for a SPI chip select.

[asalvi]

Thanks Don,

you're right the atmel document has all the pinout information. Thanks also for the SPI help. As you suggest I will use B.0 (SS) for chip select.

Another question: I see that the pin names (B.0, B.1, etc) on the Atmel match the pins on the dev board (B.0, B.1, etc.) However in the zx1280 dev board reference manual on the schematics on page 9 the pins go from 1 to 8. So for example B.0 is actually B.1 in the drawing. Is there a reason for this?

Alex

[dkinzer]

[In] the zx1280 dev board reference manual on the schematics on page 9 the pins go from 1 to 8. So for example B.0 is actually B.1 in the drawing. Is there a reason for this?

Those are pin numbers - they don't necessarily indicate the function of the pin. The B.0 function is on pin 1 of the Port B connector.

[asalvi]

Oh I see. Just seems like it would make more sense to have everything show the same name. Oh well

Thanks again Don

Alex

[dkinzer]

[It] seems like it would make more sense to have everything show the same name.

It may be that you're confusing the purpose of a pin number and that of a signal name. On the schematic, the numbers shown on the connector block labeled J3 (Port C) are the pin numbers of the connector. In general, the pin numbers don't have any relationship to the names of the signals that appear on the pins.

In the case of the port connectors, it just happens that bit zero of each port appears on pin 1 of the connector. You'll notice that there is silk screen printing on the board near each port connector that shows the port name (e.g. Port C) and the bit numbers of the port. Only bits 0 and 7 are marked. The zero silk screened near pin 1 of J3 implies that the signal on that pin is C.0. Similarly, the seven near pin 8 of J3 implies C.7.