Portsdown 4 GPIO Connections
RPi 4 GPIO pin out
- Note the RPi4 (only) can be powered with 5v directly on to GPIO 2 and 4.
GPIO Connections for the Portsdown 4
Due to a reassignment of the GPIO pins on Raspberry Pi4, the connections are different to previous generations of Portsdown.
There are 2 GPIO pins that have changed for the RPi 4. The important one is the Band LSB (or D0) which has moved from pin 28 to pin 32.
Pin 32 is available on the GPIO breakout board as the "I" pin which is pin 2 on J03. More details here: Media:PORTSDOWN INTERFACE SCH.pdf
The other changed pin is the LE line for the ADF4351 (was on 27, now pin 33) which is only used if you are using an ADF4351 for the Portsdown Signal Generator. So, generally no need to worry about this one. This isn't true if your Portsdown has an attenuator card fitted! Move the LE wire with its 1 K ohm resistor to the Q terminal.
The Portsdown 4 GPIO Connections are defined here: Portsdown 4 GPIO Connections.
List of GPIO connections
| Pin No | BCM No | Wiring Pi | RPi Pri | RPi Alt0 | Primary Use | Secondary Use | Notes & GPIO breakout board connections |
|---|---|---|---|---|---|---|---|
| 1 | - | - | 3.3v | - | - | - | - |
| 2 | - | - | 5v | - | - | - | - |
| 3 | 2 | 8 | GPIO 2 | SDA1 | I2C Control | MCP3002 Data in | - |
| 4 | - | - | 5v | - | - | - | - |
| 5 | 3 | 9 | GPIO 3 | SCL1 | I2C Control | MCP3002 LE | - |
| 6 | - | - | 0v | - | - | - | - |
| 7 | 4 | 7 | GPIO 4 | GPCLK0 | Band D2 (T) | Langstone band D2 | Label 7 on J07. "T" on 8 band boards |
| 8 | 14 | 15 | GPIO 14 | TXD0 | ADF5355 LE | Elcom, Nort SLO and AD9850 LE | For Sig Gen |
| 9 | - | - | 0v | - | - | - | - |
| 10 | 15 | 16 | GPIO 15 | RXD0 | Atten LE | - | Label 10 on J07 |
| 11 | 17 | 0 | GPIO 17 | FL1 | - | Langstone PTT Demand in | Active low |
| 12 | 18 | 1 | GPIO 18 | SPI6_CE0_N | Transmit Demand | Langstone CW Key in | Label 12 on J07 |
| 13 | 27 | 2 | GPIO 27 | SD0_DAT3 | "Active" LED | - | Active high. Label LED on J06 |
| 14 | - | - | 0v | - | - | - | - |
| 15 | 22 | 3 | GPIO 22 | SD0_CLK | Shutdown Button | - | Active high. Label PB on J06 |
| 16 | 23 | 4 | GPIO 23 | SD0_CMD | Band D4 | Langstone band D4 | - |
| 17 | - | - | 3.3v | - | - | - | - |
| 18 | 24 | 5 | GPIO 24 | SD0_DAT0 | - | Langstone band D5 | - |
| 19 | 10 | 12 | GPIO 10 | SPI0_MOSI | - | Langstone band D6 | - |
| 20 | - | - | 0v | - | - | - | - |
| 21 | 9 | 13 | GPIO 9 | SPI0_MISO | - | Langstone band D7 | Set lo for P'down, hi for L'stone |
| 22 | 25 | 6 | GPIO 25 | SD0_DAT1 | Band D3 | Langstone band D3 | - |
| 23 | 11 | 14 | GPIO 11 | SPI0_SCLK | - | - | - |
| 24 | 8 | 10 | GPIO 8 | SPI0_CE0_N | - | - | - |
| 25 | - | - | 0v | - | - | - | - |
| 26 | 7 | 11 | GPIO 7 | SPI0_CE1_N | - | Noise source | Battery Test Load Switch |
| 27 | 0 | 30 | ID_SD | SDA0 | (was ADF4351 LE) | - | DO NOT CONNECT |
| 28 | 1 | 31 | ID_SC | SCL0 | (was Band D0) | (was Langstone band D0) | DO NOT CONNECT |
| 29 | 5 | 21 | GPIO 5 | GPCLK0 | spi clock | - | Label CLK on J04 |
| 30 | - | - | 0v | - | - | - | - |
| 31 | 6 | 22 | GPIO 6 | GPCLK2 | spi data | - | Label DAT on J04 |
| 32 | 12 | 26 | GPIO 12 | PWM0 | new Band D0 | new Langstone band D0 | Band select LSB. Label I on J03 |
| 33 | 13 | 23 | GPIO 13 | PWM1 | new ADF4351 LE | - | Label Q on J03 |
| 34 | - | - | 0v | - | - | - | - |
| 35 | 19 | 24 | GPIO 19 | SPI6_MESO | Band D1 | Langstone band D1 | Band Select MSB on J05 |
| 36 | 16 | 27 | GPIO 16 | FL0 | - | - | SR select LSB D0 on J02 |
| 37 | 26 | 25 | GPIO 26 | SD0_DAT2 | - | - | SR select NSB D1 on J02 |
| 38 | 20 | 28 | GPIO 20 | SPI6_MOSI | - | D-A LE | SR select MSB D2 on J02 |
| 39 | - | - | 0v | - | - | - | - |
| 40 | 21 | 29 | GPIO 21 | SPI6_SCLK | TX LED/PTT Drive out | - | TX LED J05 |
Note that the GPIO pin names are markedly different from the RPi 3B. Each pin on the RPi4 GPIO can be referred to in many ways: its physical pin number, the Broadcom I/O number, the Wiring Pi number or the primary or alternate names. Source for GPIO designations was the Raspberry Pi 4 Model B datasheet.
Note that no connections should be made to GPIO Pins 27 and 28, otherwise the RPi might get stuck on the Rainbow Screen at boot. Previous connections to these pins are being moved to other pins 32 and 33.
J0x terminal block identities relate to the BATC GPIO breakout PCB from the club shop..
Unused Willow breakout boards may work with Portsdown 4 because they needed extra connections to pins 27 & 28 on Portsdown 2018. These aren't required on P4 as noted here.
Pins 36, 37 & 38 are still connected for extra DO, D1 & D2 connections. These are used with the 2-way RF Switch - F-M port of which is connected to the Pluto. All 3 lines are sent to logic high (3.3V) in Portsdown 2019 / 2020 and in the 4 on transmit and this switches in the Lime Mini.