Yes, this working great, here are the overlay rising edge changes -
/*
* Copyright (c) 2022 Da Xue
* Author: Da Xue <da@libre.computer>
*
* SPDX-License-Identifier: (GPL-2.0+ OR MIT)
*/
/*
* Overlay aimed to create pps-gpio on 7J1 pin 12 (GPIOAO_6)
* This requires an GPIO to IRQ enabled kernel and will not work without one.
*/
/*
* Edited to switch interrupt to rising edge
*
/
/dts-v1/;
/plugin/;
#include <dt-bindings/gpio/gpio.h>
#include <dt-bindings/gpio/meson-gxl-gpio.h>
#include <dt-bindings/interrupt-controller/irq.h>
#include <dt-bindings/interrupt-controller/meson-gic.h>
/ {
compatible = "libretech,cc", "amlogic,s905x", "amlogic,meson-gxl";
fragment@0 {
target-path = "/";
__overlay__ {
pps_gpio: pps-gpio {
compatible = "pps-gpio";
pinctrl-names = "default";
pinctrl-o = <&spdif_out_ao_6_pins>;
gpios = <&gpio_ao GPIOAO_6 GPIO_ACTIVE_HIGH>;
interrupts = <&gpio_intc MESON_GIC_GXL_GPIOAO_6 IRQ_TYPE_EDGE_RISING>;
assert-rising-edge;
status = "okay";
};
};
};
};
This is the version I used, have trouble with the includes -
/*
* Copyright (c) 2022 Da Xue
* Author: Da Xue <da@libre.computer>
*
* SPDX-License-Identifier: (GPL-2.0+ OR MIT)
*/
/*
* Overlay aimed to create pps-gpio on 7J1 pin 12 (GPIOAO_6)
* This requires an GPIO to IRQ enabled kernel and will not work without one.
*/
/*
* Modified to switch to rising edge interrupt and
* Modified to remove symbols so can be compiled without includes
*/
/dts-v1/;
/plugin/;
/*
#include "/boot/mydt/dt-bindings/gpio/gpio.h"
#include "/boot/mydt/dt-bindings/gpio/meson-gxl-gpio.h"
#include "/boot/mydt/dt-bindings/interrupt-controller/irq.h"
#include "/boot/mydt/dt-bindings/interrupt-controller/meson-gic.h"
*/
/ {
compatible = "libretech,cc", "amlogic,s905x", "amlogic,meson-gxl";
fragment@0 {
target-path = "/";
__overlay__ {
pps_gpio: pps-gpio {
compatible = "pps-gpio";
pinctrl-names = "default";
pinctrl-o = <&spdif_out_ao_6_pins>;
gpios = <&gpio_ao 6 0>; /* =<&gpio_ao GPIOAO_6 GPIO_ACTIVE_HIGH>; */
interrupts = <&gpio_intc 6 1>; /* =<&gpio_intc MESON_GIC_GXL_GPIOAO_6 IRQ_TYPE_EDGE_RISING>; */
assert-rising-edge;
status = "okay";
};
};
};
};
Compile the above with this command -
#dtc -I dts -O dtb pps-gpio-7j1-12-rising.dts -o pps-gpio-7j1-12-rising.dtbo
Copy into place prior to merge where ever your overlays are located ??libretech-wiring-tool/libre-computer/aml-s905x-cc/dt/
Here is a quick synopsis of the procedure I used to get this working -
Physical Connection to the GT-U7 gps module.
5v in, 3.3v pps and serial signals
GPS 7j1 Pin
Vin ----- 4, 5volts
Gnd ----- 6, Ground
Tx ----- 5, UART_RX_AO_B
Rx ----- 7, UART_TX_AO_B
PPS ----- 12, GPIOAO_6 -The magic interrupt
Pre req - Le Potato running - 2022-09-22-raspbian-bullseye-arm64+aml-s905x-cc.img
- pps-gpio modified for rising edge see post above
Here we go -
#apt update
#apt upgrade
#apt install linux-image-6.1.y-lts-irq-arm64
#apt install gpsd
#apt install chronyc
#apt install pps-tools
#git clone https://github.com/libre-computer-project/libretech-wiring-tool.git
#cd libretech-wiring-tool/
#./install.sh
//Overlay modified to use rising edge if interrupt
#ldto merge pps-gpio-7j1-12-rising
#ldto merge uart-ao-b
#reboot
//well lookee here !!
pi@raspberrypi:~ $ dmesg|grep pps
[ 0.663946] pps_core: LinuxPPS API ver. 1 registered
[ 0.663960] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <giometti@linux.it>
[ 8.733323] pps pps0: new PPS source pps-gpio.-1
[ 8.733399] pps pps0: Registered IRQ 42 as PPS source
pi@raspberrypi:~ $
---------- chrony.conf ------------------
//add the follwing lines, optionally delete unneeded servers/pools
#nano /etc/chrony/chrony.conf
# PPS from the pps-gpio interrupts
refclock PPS /dev/pps0 refid PPS0 prefer precision 1e-5
# Serial data from ttyAML2. offset is the estimate of the fraction of
# a second the serial data arrives behind the pps. Found experimentally.
refclock SHM 0 refid AML2 offset 0.126 precision 1e-1
-------------------------------------------
-----------gpsd.service file---------------
#nano /usr/lib/systemd/system/gpsd.service
//Change the Exec line to -
ExecStart=/usr/sbin/gpsd -n -s 9600 /dev/ttyAML2
--------------------------------------------
#reboot
Hopefully you are golden in 5 or 30 minutes -
pi@raspberrypi:~ $ chronyc sources
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
#* PPS0 0 4 377 14 +547ns[ +639ns] +/- 10us
#- AML2 0 4 377 15 -4707us[-4707us] +/- 100ms
^- time2.google.com 1 8 377 172 -3059us[-3058us] +/- 15ms
^- time-d-b.nist.gov 1 8 377 171 -2999us[-2998us] +/- 12ms
pi@raspberrypi:~ $
Thats under 1 us accuracy stratum 1 ntp server for about $50 (Le Potato=$35 + GT-U7=$10)! (Does fluctuate up to 2 or 3 us occasionally)
2 Likes
Thanks. We have updated the overlay in the repo.
2 Likes
wigyori
24
Hmm, would this work on an S805x (La Frite) on 7J1 / 35 ? That’s PWM_F there, which also seems to be an IRQ-capable pin (used as SDIO_IRQ if needed).
PPS works on any pin on any of our platforms.