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RPi WH accessory board? — Parallax Forums

RPi WH accessory board?

RaymanRayman Posts: 14,012
in Propeller 2
I'm wondering if Parallax should think about adding a Raspberry Pi WH interface board...

Would be a very simple board, I think with just a 40-pin female header...
I've just been playing around with RPi W and think it can add a lot for very little $$...

One think I'm working on is using the RPi as a GPU using OpenVG over the SPI interface.
Looks like wiringPi will allow up to 26 MHz bidirectional over SPI...

Comments

  • RaymanRayman Posts: 14,012
    BTW: I'm also thinking that this will let me connect RPi to old Arcade Monitor.
    I'm pretty sure P2 will be able to do the 15 kHz video those old monitors need...
  • jmgjmg Posts: 15,149
    edited 2019-11-12 19:42
    Rayman wrote: »
    I'm wondering if Parallax should think about adding a Raspberry Pi WH interface board...

    Would be a very simple board, I think with just a 40-pin female header...
    I've just been playing around with RPi W and think it can add a lot for very little $$...
    Yes, Pi support should be on all boards ;)

    Here are the pinouts I evolved to, this allows full 32 P2-io access, and pi serial compatible links and is 2 layer compatible for routing.

    Two approaches are possible :

    Same-Side Pi 
                                   CN3
                              .___.              
VBP                  +3V3---1-|O O|--2--+5V                     5V 
P31          (SDA)  GPIO2---3-|O O|--4--+5V                     5V 
P30         (SCL1)  GPIO3---5-|O O|--6--_                       GND
P28    (GPIO_GLCK)  GPIO4---7-|O O|--8-----GPIO14 (TXD0)        P29
P26j    PiGND            _--9-|O.O|-10-----GPIO15 (RXD0)        P27
P24    (GPIO_GEN0) GPIO17--11-|O O|-12-----GPIO18 (GPIO_GEN1)   P25
P22    (GPIO_GEN2) GPIO27--13-|O O|-14--_          PiGND        P23j
P20    (GPIO_GEN3) GPIO22--15-|O O|-16-----GPIO23 (GPIO_GEN4)   P21
VAP                  +3V3--17-|O O|-18-----GPIO24 (GPIO_GEN5)   P19
P17     (SPI_MOSI) GPIO10--19-|O.O|-20--_          PiGND        P18j
P15     (SPI_MOSO) GPIO9 --21-|O O|-22-----GPIO25 (GPIO_GEN6)   P16
P13     (SPI_SCLK) GPIO11--23-|O O|-24-----GPIO8  (SPI_C0_N)    P14
GND                      _-25-|O O|-26-----GPIO7  (SPI_C1_N)    P12
P10       (EEPROM) ID_SD---27-|O O|-28-----ID_SC ID EEPROM      P11
P8                 GPIO5---29-|O.O|-30--_   PiGND               P9j
P6                 GPIO6---31-|O O|-32-----GPIO12               P7 
P5                 GPIO13--33-|O O|-34--_                       GND
P3                 GPIO19--35-|O O|-36-----GPIO16               P4 
P1                 GPIO26--37-|O O|-38-----GPIO20               P2 
GND                      _-39-|O O|-40-----GPIO21               P0 
                              '---'
                       40W 0.1" PIN HDR

    and FLiP Pi, this reverses the order, so connects from other PCB side, and doing this allows SCL1 SDA1 to move clear of the Boot-pins on the upper header.
    Like P1 FLiP, this allows better silkscreen naming and labeling. 
           PI4  P2D2Pi FLiP                       CN1  (Other 40 pin, CN3 Pm = P(n-32 ))                
       P2     Pi4      Std Pi                .___.               Std Pi       Pi4     P2
       VBP                          +3V3---1-|O O|--2--+5V                            5V 
       P32                 (SDA1)  GPIO2---3-|O O|--4--+5V                            5V 
       P33                 (SCL1)  GPIO3---5-|O O|--6--_                              GND
       P35    TXD3    (GPIO_GLCK)  GPIO4---7-|O O|--8-----GPIO14 (TXD0)               P34
       P37j            PiGND            _--9-|O.O|-10-----GPIO15 (RXD0)               P36
       P39            (GPIO_GEN0) GPIO17--11-|O O|-12-----GPIO18 (GPIO_GEN1)          P38
       P41            (GPIO_GEN2) GPIO27--13-|O O|-14--_          PiGND               P40j
       P43            (GPIO_GEN3) GPIO22--15-|O O|-16-----GPIO23 (GPIO_GEN4)          P42
       VBP                          +3V3--17-|O O|-18-----GPIO24 (GPIO_GEN5)  PWM0    P44
       P46            (SPI0_MOSI) GPIO10--19-|O.O|-20--_          PiGND               P45j
       P48            (SPI0_MOSO) GPIO9 --21-|O O|-22-----GPIO25 (GPIO_GEN6)          P47
       P50            (SPI0_SCLK) GPIO11--23-|O O|-24-----GPIO8  (SPI0_CE0_N)         P49
       GND                              _-25-|O O|-26-----GPIO7  (SPI0_CE1_N) RTS3    P51 
       P53    SDA0       (EEPROM) ID_SD---27-|O O|-28-----ID_SC ID EEPROM     SCL0    P52
       P55    RXD3                GPIO5---29-|O.O|-30--_                              P54j
       P57    CTS3                GPIO6---31-|O O|-32-----GPIO12              PWM0    P56
F.IO1  P58    PWM1                GPIO13--33-|O O|-34--_                              GND
F.CLK  P60                        GPIO19--35-|O O|-36-----GPIO16                      P59  F.IO0
U.TXD  P62                        GPIO26--37-|O O|-38-----GPIO20                      P61  F.CSN 
       GND                              _-39-|O O|-40-----GPIO21                      P63  U.RXD
                                             '---'                                  
                                      40W 0.1" PIN HDR
  • RaymanRayman Posts: 14,012
    One thing I'm still getting a handle on is the GPIO numbering...
    There are two main schemes: wiringPi and BCM
    I think you show the BCM numbers.

    The Visual Studio example that I'm starting from is using the BCM scheme.
    But, I think I'd rather use wiringPi.
    But, there's something about BCM allowing you to not run as superuser. Not sure how important that is yet...
  • RaymanRayman Posts: 14,012
    edited 2019-11-12 20:29
    BTW: I don't think you want to connect the +3V3 supply pins.

    Also, the 5V supply is a bit of a problem... I've heard Pi Zero W can draw a lot of power.
    And, I hear that P2 may draw a lot of power..

    The ES board has a 2 A connector, I believe. That should be enough for both, but not 100%.

    I think I may have messed up the filesystem on my first Pi uSD by not giving it enough power (only had 500 mA, not certain about this though).
  • jmgjmg Posts: 15,149
    edited 2019-11-12 21:23
    Rayman wrote: »
    One thing I'm still getting a handle on is the GPIO numbering...
    There are two main schemes: wiringPi and BCM
    I think you show the BCM numbers.

    The Visual Studio example that I'm starting from is using the BCM scheme.
    But, I think I'd rather use wiringPi.
    But, there's something about BCM allowing you to not run as superuser. Not sure how important that is yet...

    Yes, I did not pay much attention to nn in the GPIOnn general IO pins, as the primary focus was on supporting serial UART/i2c/SPI peripheral boards, and if someone wants to use a parallel IO LCD (rare), they can map LCD in LUT for example. That keeps the PCB layout compact and more direct.
    Of more interest than parallel LCD, are the faster 125MHz SPI LCDs (2.8" to 4" are common)

    Google finds this about WiringPi http://wiringpi.com/wiringpi-deprecated/
    Rayman wrote: »
    BTW: I don't think you want to connect the +3V3 supply pins.

    Also, the 5V supply is a bit of a problem... I've heard Pi Zero W can draw a lot of power.
    And, I hear that P2 may draw a lot of power..

    Yes. There will be fish-hooks & many combinations.
    Where P2 is used to host a Pi HAT, you may need to bridge the 3v3 jumpers (depends on how it powers), but where P2 is used as a Pi slave, you may want to separate the 3v3 supplies.

    On P2D2Pi FLiP, you can do both, as it has 2 identical Pi 40 pinned connectors.
    You can connect a Pi board to one 40 pin connector, and use the other 40 pin header as a HAT connection, making P2 a bridge element.

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