How does Microsoft.SPOT.Hardware.Cpu.Pin work?

NETMF & Gadgeteer
1

Something I never thought much about. (Guess I should have)

Use to my Spider (Just does it’s thing from Visual Studio) and I never have to worry…

My ChipworksX and G400-D a different matter.

Example using the common Gadgeteer Button Module on a G400HDR

X9 PU Y
Socket 9 Pin 3 G400_96 ( JP1_35, PB18 / IRQ / ADTRG )
Socket 9 Pin 4 G400_200 ( JP1_3, PA7 / TXD2 ) - (COM4 TXD / SPI0 NPCCS1)

Using Socket 9 Pin 4 for OutputPort

(Cpu.Pin)G400.Pin.PA7 ID returns GPIO_Pin7
(The Gadgeteer Button module LED)

Using Socket 9 Pin 3 InterruptPort

(Cpu.Pin)G400.Pin.PB18 ID returns 50
(The Gadgeteer Button module switch output)

(Cpu.Pin)G400.Pin.PA7 ID = GPIO_Pin7 maps to G400-D processor Pin 200
(??? on schematic)

(Cpu.Pin)G400.Pin.PB18 ID = 50 maps to G400-D processor Pin 96 (PC6)

I do not see the relation of the ID to the actual processor pin number.
Can someone explain this to me?


using G400 = GHI.Hardware.G400; //FEZ Hydra

static OutputPort LED;
static InterruptPort Socket9Button;

LED = new OutputPort((Cpu.Pin)G400.Pin.PA7, true);
Debug.Print("Button LED using pin: " + LED.Id.ToString());

Socket9Button = new InterruptPort((Cpu.Pin)G400.Pin.PB18, false,
                Port.ResistorMode.PullUp, Port.InterruptMode.InterruptEdgeBoth);
Debug.Print("Button interrupt using pin: " + Socket9Button.Id.ToString());

The code works.

Visual Studio Debug Output
Button LED using pin: 7
Button interrupt using pin: 50

Thanks…

2

A MCU can be provided in different packages, even with different number of pins (balls). So PA7 can be a pin 1 or 200, or any other pin on the physical chip.

In G400 case it is not even a chip’s pin, but the pin on the socket. And it happens that PA7 was routed to pin 200 on the socket by GHI.

3

@ Architect -

So PA7 can be a pin 1 or 200, or any other pin on the physical chip.

‘or any other pin on the physical chip’ That is why I was asking…

MCU I’m not sure I know what that is. Does the Premium library provide it?
Something I can look at?

4

MCU - microcontroller unit.

I am not sure we will have schematics of the actual G400 unit, but the pinout information is more than enough in this case.

http://www.ghielectronics.com/downloads/beta/G400/G400_D_Module_Brochure.pdf

5

Also, in pin relation, MCUs have a number of General Purpose Input and Output pins (GPIO) that, when enumerated, start out usually at 0 and go to the maximum GPIOs available.

In the case of G400, there are 32 pins on 4 different ports, A, B, C, and D. which would lead to an approximate total of 32 x 4 = 128 (port D is fewer than 32). So, a math equation of (Port * 32) + Pin is usually the key to understanding the relation. For PA7 to equal pin ID 7 you take (0 * 32) + 7 will equal 7 and PB18 equals (1 * 32) + 18 to equal pin ID 50.

For the Cerb family, the ports only go to 16 but the general equation will work the same.

2 Likes
6

@ Aron -

Thanks!

I copied your text and put it in my notes folder… I’ll study it later and write some tests and see what happens.

As a side note:

I wanted to know so I do not try to write a digital port voltage to some pin that does not like a digital level (Maybe this is not even possible) but I do stupid things at times…

7

@ Architect -

MCU I was thinking you we talking about some kind of translation table in code…

8

just for future reference: when the beta period is over, the brochure will be maintained at http://www.ghielectronics.com/downloads/man/G400_D_Module_Brochure.pdf right now we have it in two places so all the beta materials can be found in one folder.