Unravel unknown thermistor
Recently I made mistake and made PCB for arduino module where connect temperature sensor to A7 PIN. I’ve envisaged that sensor could be analog (diode) or digital. Soon I’ve learned that diode doesn’t provide enough accuracy even for ±5℃ (2mV/℃) and surprise-surprise A7 pin is only analog input so I can’t use DS18B.
I had haven’t any other temp sensors, fortunately I’ve remembered that I have broken battery controller from laptop and it should have some sort of temp sensor, here it is: 
I’ve poked it with multimeter few times to be sure that it isn’t semiconductor sensor, but NTC with near 10K Ohm resistance at 25℃. I’ve decided to use it, but don’t know how much Ohm/℃ it has. I’ve planned to use linear approximation to convert resistance to temp, so i measure few points and here what i got:
Here is ADC value on X-Axis and temperature on Y-Axis. Pure perfect, i could use it with one pair of a and b coefficients in temperature range which i want.
Posted in Hardware | Tags: hardware | No Comments
Dirty hack to add values mappings in Zabbix
“I’ll be brief.” ©
Here is two things about script published in ZBXNEXT-1424, first it can help you to automate creation of large mappings (and it’s cool), second it will broke your DB (not so cool, maaan).
When you will try to add mapping in broken DB you will see something like this:
The “Error in query [INSERT INTO valuemaps (name,valuemapid) VALUES (‘Test mapping’,’50’)] [Duplicate entry ’50’ for key ‘PRIMARY’]” mean, that in table valuemaps you already have entry with valuemapid = 50. Why it happened i tell later after we fix DB.
To fix DB, you need to update few entries in table ‘idx‘, first update nextid where table_name = valuemaps:
mysql> update ids set nextid = (select max(valuemaps.valuemapid)+1 from valuemaps) where table_name = 'valuemaps'; Query OK, 1 row affected (0.22 sec) Rows matched: 1 Changed: 1 Warnings: 0 |
Second update nextid for mappings:
mysql> update ids set nextid = (select max(mappings.mappingid)+1 from mappings) where table_name = 'mappings'; Query OK, 1 row affected (0.22 sec) Rows matched: 1 Changed: 1 Warnings: 0 |
Here it is!
This happened because script does not update table idx. May be it’s ok for zabbix 2.0 that mentioned in feature request, but it’s broke database for zabbix 2.2 and newer. Unfortunately zabbix prior version 3.0 does not have API or ability to import mappings , so that script still useful.
Here is fixed script, i hope author will not offended at me:
#!/usr/bin/perl use warnings; use strict; my $usage = "$0 valueMapName number newvalue [number2 newvalue2 [...]] E.g.: $0 'Alarm Status' 1 ok 2 unknown 3 stale 4 problem $0 'Aliveness' 0 dead 1 alive "; my $valueMapName = shift() || die "No new valuemap name"; my @mapList = @ARGV; die "No mappings given. Usage: $usage\n" if scalar(@mapList) == 0; my $isEvenNumber = scalar(@mapList) % 2 == 0; die "Must give mapping->value pairs. Usage: $usage\n" if not $isEvenNumber; my %mappings = @mapList; my $newValueMapId = int(qx/mysql -N -s -e 'select nextid from zabbix.ids where field_name = "valuemapid"'/) || die("Can't fetch max valuemapid\nUsage: $usage\n"); $newValueMapId++; my $newMappingId = int(qx/mysql -N -s -e 'select nextid from zabbix.ids where field_name = "mappingid"'/) || die("Can't fetch max mappingid\nUsage: $usage\n"); $newMappingId++; eval { my $valueMapCmd = qq/mysql -e "insert into zabbix.valuemaps (valuemapid, name) values ('$newValueMapId', '$valueMapName');"/; print "$valueMapCmd\n"; system $valueMapCmd; eval { for my $from (keys %mappings) { my $to = $mappings{$from}; my $mappingCmd= qq/mysql -e "insert into zabbix.mappings (mappingid, valuemapid, value, newvalue) values ('$newMappingId', '$newValueMapId', '$from', '$to');"/; print "$mappingCmd\n"; system $mappingCmd; $newMappingId++; } }; if ($@) { die "something went wrong inserting into mappings $@"; } }; if ($@) { die "something went wrong inserting into valuemaps $@"; } my $valueMapUpdCmd = qq/mysql -e 'update zabbix.ids set nextid = "$newValueMapId" where field_name = "valuemapid";'/; print "$valueMapUpdCmd\n"; system $valueMapUpdCmd; $newMappingId--; my $mappingUpdCmd = qq/mysql -e 'update zabbix.ids set nextid = "$newMappingId" where field_name = "mappingid";'/; print "$mappingUpdCmd\n"; system $mappingUpdCmd; |
Posted in Linux related | Tags: linux, monitoring, mysql, repair, zabbix | No Comments
KIS-3R33 calculator
Half year ago i wanted to get in car PSU to charge my smartphone or to power devices like camcoder. I wanted to build powerful power supply, first i tried to build it on chip NCP3155, but has failed. I lurking around to find another chip and found complete module KIS-3R33 based on MP2307 chip. I found it very interesting and cheap, after i got few i started to find way how to change output voltage from 3.3V to 5V. I found many guides how to change Vout, by replacing internal components and all of them ignore the fact, that module have Adjust pin. I wanted to find way how to change Vout without replacing internal components.
KIS-33R3 very similar to typical application:
Datasheet give ratio for calculation of Vout depend of R1 and R2:
Vout = 0.925* (R1 + R2) / R2
According to scheme of module that i found into the internet, Adjust pin connected to FB in series with resistor of 3.3kOhm:
R1 = 25.5 kOhm (two 51kOhm resistors in parallel), so it is possible to vary R1 in range 25.5 kOhm – 2.9 kOhm and R2 in range 10 kOhm – 2.48 kOhm it give output range 1.19V – 10.43V. If you need voltage more than 5V, you need to remove zener diode first (D2 on scheme), because this diode limit Vout to 5.1V. Also voltage range of output capacitor (C2 on scheme) is not know, so it is good idea to replace it with capacitor that can handle your output voltage.
I wrote simple calculator for KIS-3R33 that compute resistor that you must connect between Adj pin and GND or Vout to get desired voltage. Don’t forget, that result will correct only for KIS-3R33 that have 3.3V output (i seen version that have 2.7V output, so be careful).
Posted in Hardware | Tags: hardware | No Comments
Libvirt + vnc + sasl
Yesterday i wanted to configure libvirt with kvm virtualization, while i read comments in config file, i observed, that qemu can share credentials with libvirt via sasl. Also i found few how-to, that said ‘just copy /etc/sasl2/libvirt.conf to /etc/sasl2/qemu.conf’.
I done that, but when i tried to open console of VM i got “Error: connection to hypervisor host got refused or disconnected!”.
May be you think, that you can find something interesting in log? Nope. May be you think that you can run virt-manager in debug mode and will see something useful? Nope. The reason, why this happened is because, libvirt run as root, but they start VM’s as libvirt-qemu user. And sasl2 database has owner root:root and 640 permissions. I changed owner of /etc/libvirt/passwd.db to libvirt-qemu:root and problem is gone.
Posted in Linux related | Tags: bug, debian, kvm | No Comments
STM32 performance test or how fast you can serve input signal
Finally, i decided to try stm32, before i wrote firmwares only for AVR mega family (from now, when i say AVR MCU, i mean AVR mega family MCU), and was scared by tonns of code that you need for simply led blinking on STM32 MCU.
Now i can say, that programming of STM32 not so hard as it looks first time. After i understand logical structure of MCU core and how it work, it become easy.
OK, it was prelude.
Every time when i see comparison between AVR and STM32/STM8 MCU’s i faced with next arguments:
STM MCU’s have lower price, when they have more RAM, FLASH, GPIO pins and work frequency. Looks sweet. Today i want to tell the story about work frequency.
More than the operating frequency of the MCU, the faster it can handle events. STM32 MCU’s have maximum work frequency more than 20MHz (72MHz for STM32F103 that i have), when AVR MCU’s have only 20MHz. Is 72MHz a lot of or not? Two week ago i wanted to know, is it enough ~200MHz of STM32F4 to handle 10MSPS ADC on not? Two weeks ago i think ‘may be’. Now i think ‘not enought’.
Last Friday evening i blow the dust from oscilloscope and made little research.
My basic code poll pin, by software, configured for input and set same signal on output pin, the code is there:
while(1) { if( GPIOB->IDR & GPIO_IDR_IDR10 ) { GPIOB->BSRR = GPIO_BSRR_BS8; } else { GPIOB->BSRR = GPIO_BSRR_BR8; } } |
How many time MCU need to set same level on GPIO pin as on input pin? May be 140nS (near 10 clocks on 72MHz) will enought?
Nope. 480ns. It near 34 cycles. The period of 480ns has frequency of 2MHz, may be i forgot to change speed of gpio port?
Nope. May be i forgot to switch on external quartz or forgot to configure PLL?
Nope. Hmm, may be optimization can help? Let’s try to switch on -O3:
Much better, 170 ns. MCU need near 12 cycles, to detect signal and change state of one GPIO speed. Do not forget, MCU just pooling one pin and change state of another, it do not do valuable work.Okay, but what the maximum speed you can get, if you will just change the state of GPIO pin?
Is it possible to hit theoretical maximum of 50MHz (max clock speed of GPIO ports on STM32F103):
Just 6MHz. Let me switch on optimization for you:
Looks like there only 36MHz, let’s look on the code:
I can’t see why they can’t reach 50MHz. If you look on disassembler view, you can see, that MCU just store different values on constant address.
In fairness i must to say, if you set cursors on oscilloscope in different manner, you can achieve 50MHz:
It is hard to say what way of measurement is wrong, i think the second, because first time it is easy to see time of 2 periods. Without a doubt, the second way STM advertising department would have liked more.
BONUS:
A picture where is while cycle occurs:
Posted in Hardware | Tags: C, hardware, stm32 | 4 Comments