Unfortunately you can't just choose random pins for hardware functions. Each GPIO supports a specific set of alternate functions. You can find a table on page 15 of the RP1 datasheet (https://datasheets.raspberrypi.com/rp1/ ... herals.pdf), or run "pinctrl funcs 25" to show your options:The first line line shows that the first alternate function (a0) of GPIO17 is SPI1_CE1, the second (a1) is DPI_D13, etc. RTS0 (the RTS signal for UART0) is a4. However, looking at GPIO25 shows that none of its alternate functions involve UART0, and definitely not RTS0.
You might be able to write some code to rapidly poll the level of GPIO17 and echo it to GPIO25, but that would slow things down a bit. A mod wire would be better.
Code:
pi@raspberrypi:~$ pinctrl funcs 17,2517, GPIO17, SPI1_CE1, DPI_D13, DSI1_TE_EXT, -, RTS0, SYS_RIO017, PROC_RIO017, PIO17, -25, GPIO25, SD0_DAT1, DPI_D21, I2S0_SDO2, MIC_CLK, I2S1_SDO2, SYS_RIO025, PROC_RIO025, PIO25, SPI3_CE1You might be able to write some code to rapidly poll the level of GPIO17 and echo it to GPIO25, but that would slow things down a bit. A mod wire would be better.
That's GPIO25 on the main BCM2712 SoC, not RP1. It's permanently wired to the Bluetooth modem (if it is fitted). You want "pinctrl 25".Moreover, I believe I need to disable bluetooth first, as pinctrl gives me:at the moment.Code:
125: a4 pu | hi // BT_CTS/GPIO25 = UART_CTS_0
Statistics: Posted by PhilE — Tue May 13, 2025 6:47 pm