Could you explain us the use of the BAV116W diode please in the ADC circuitry example on this article ? I would like to add ESD protection to adc inputs, is this diode enough?
The diode between ground and the signal as shown in the adc page is used to clamp the voltage on the AD line in order to avoid it goes under 0V (-1V roughly). It is a good protection for reverse voltage made by mistake from the user and also a good protection against ESD especially after the resistor divider and the capacitor.
The resistor divider, is useful to limit a lot the spike current in case of a spark. This spike is also shorted to ground by the capacitor.
In order to fufther improve the protection of the ADC input you can add another diode between the ADC line (anode) and the power rail (cathode) as shown as optional in our Daisy 20 board.
And finally you can add on your input connector some spark-gap as shown in this photo:
You need to form a 0.2mm gap between uncovered by solder resist ADC input and ground pads with sharp copper tips. A spark arriving will choose hopefully this path instead of crossing the input resistor and produce more damage to the circuit.
"Everytime I try to power down my Arietta via shutdown -h now or halt it reboots immediately afer it shuts down. What is my mistake? Or has my board any defect? Or how to power ist down properly ?"
On the Arietta, the Shutdown line is connected on the power regulator enable so to be able to put Arietta in sleep if you use a battery for the RTC.
In order to shut down Arietta properly the right command is hence
# shutdown -h -H now
In this way the shutdown command will not lower the shutdown line and you can safely remove power when the board halts.
Without the -H the shutdown line will lower at the board halt bringing down the 3V3 voltage so you are doing a very hard reset only (useful some time).
The serial port /dev/ttyS1 (used on the Terra-M to link the GPRS modem) doesn't work using the A4 microSD with Kernel 3.11.6:
Download and save the at91-ariag25.dtb file in the first microSD partition and reboot. This error is due to a wrong device tree used on the first microSD with Kernel 3.11. Here is the right definition: at91-ariag25.dts
Memory swap command causes this error:
debarm:/etc# swapon /dev/mmcblk0p4 swapon: /dev/mmcblk0p4: swapon failed: Function not implemented
The Linux Kernel is not configured to support the memory swap.
Follow this article:
and enable the memory swap in:
General setup ---> [*] Support for paging of anonymous memory (swap)
Enable the swap partition on the microSD adding these lines in /etc/fstab
#Enable the swap memory /dev/mmcblk0p4 none swap sw 0 0
Create a Linux swap partition on microSD
The reason of is problem is well explained on this post and it can be caused intentionally typing
# hwclock -w
and removing the power supply before the command ends. The problem occours only if the RTC backup battery is present.
To solve it you have to replace the AriaBoot executable file (boot.bin) on the first partition if the bootable microSD card with one of these files:
Renaming one of it in boot.bin.
The changes on AriaBoot source file are available on GitHub.
We found an insidious DDR2 RAM memory problem on the AriaG25-256. If your board already has the patch wire shown below the problem was already solved by us before shipment.
If your board has not the patch wire it could be affected by a memory fault problem highlighted only using the memtester utility.
According to our test this issue does not affect the AriaG25-128 boards (How to recognize an Aria G25 with 128MB or 256MB).
To highlight the problem install memtester on your AriaG25-256:
# apt-get install memtester
# memtester 1M
If your board fails one or more benchmarks you need to place the patch wire to avoid them. The two points to wire are the follow:
On the next production batch planned for october we'll eliminate this patch wire fixing the PCB.
Those who ordered the Aria G25 during the first and are using a Debian microSD from Acme the serial ports ttyS1,S2,S3,S4 and the I2C and 1-Wire can't enabled due a wrong kernel configuration .
The solution is to use the R4 version available on Bootable microSD card binary repository. It is enough to change just the uImage file on the first partition of the bootable SD card.
Sometime after a reboot command the FOX Board G20 hangs.
If you are using a self compiled kernel 2.6.38 uImage comment these two lines on arch/arm/mach-at91/at91sam9_alt_reset.S: and make again a uImage:
//str r2, [r0, #AT91_SDRAMC_TR] @ disable SDRAM access //str r3, [r0, #AT91_SDRAMC_LPR] @ power down SDRAM
If you are using an Acme factory default uImage download this uImage file:
Rename it in uImage and copy it on the first microSD FAT32 partition called "kernel".
You can change it remotely copying the uImage in the directory /media/mmc_p1:
$ scp uImage_reboot root@[fox IP number]:/media/mmc_p1/uImage
and rebooting the FOX.
This problem is due to a wrong production batch of ethernet connectors where the yellow led is inverted. Unfortunately is not so simple to change this connector so we could suggest to mount an external led as shown in the figure below.
Edit the file /etc/cron.weekly/apt-xapian-index end insert "exit 0" after the first line:
#!/bin/sh exit 0
Probably your FOX Board G20 mount an AcmeBoot loader version 1.19 or older. Move to the new a version 1.20 or higher (Go to AcmeBoot page).
This is due to a bug on the atmel-mci.c Kernel 126.96.36.199 driver up to September 2010. Use the the latest kernel image available on binary snapshot to avoid this problem.
If you are still using the U-boot bootloader instead of AcmeBoot with a Debian microSD higher than R03 add foxg20-script.bin on the first FAT partition of your bootable microSD or move from U-boot to AcmeBoot.
This problem is due to the Vodafone Station that automatically redirects any requests on port 80 icoming from new MAC addresses.
To solve this problem open a browser on a PC wired on the same LAN and go to the following URL changing ff:ff:ff:ff:ff:ff with the MAC address of your Acme board:
Then click on the top-right X to close the page and confirm on the next page.
Now try again with apt-get command on your Acme board.
In /etc/network/interfaces change the line:
Then test the configuration by typing:
ifdown eth0 ifup eth0
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