radioactive@home v2.61, Atmega 88 alive? - Page 1
Forum section: electronics / repair

author: OE2WHP
author_rank: Regular Contributor
timestamp: May 20, 2018, 10:02:58 am
content: Hi,a couple of years ago, I started to build a radioactive@home kit (Rev.2.61) (http://radioactiveathome.org/en/) but then never found time to finnish ist. Yesterday I stumbled upon the pcb again und finnished it. Unfortunately it does not work. The project seems to be abandoned, so no help from there.No idea what could be wrong. I doublechecked parts placement and soldering. Everything seems ok. The display shows just all pixels on in the upper row and all pixels off in the second row.5V supply voltage is there and the 20MHz oscillator works with ~1,6Vpp. Besides that, nothing really happens on the board. No PWM for the HV, no RX/TX, no display :-(The ATMega came as 'Preprogrammed' and currently I suspect it to not be programmed or to be dead. I'm not a µcontroler guy so I kind of hit a wall here.Is there anything how I could check if it's a problem of the µC or if I need to re-re-recheck the rest of the board?Any help is highly appreciatedThanks

author: Rerouter
author_rank: Super Contributor
timestamp: May 20, 2018, 10:09:17 am
content: The forum of that webpage is active as of 12 days ago, even with posted firmware, you might find better support asking there.

author: ace1903
author_rank: Regular Contributor
timestamp: May 20, 2018, 10:10:30 am
content: Check with pot for display contrast.Sometime if contrast is set incorrectly it will show all pixels black.Lowering contrast will show the text.Does buzzer responds to button clicks?If not then check if micro is programmed and live.

author: OE2WHP
author_rank: Regular Contributor
timestamp: May 20, 2018, 10:15:15 am
content: No the forum is dead. Just some recent spam posts, keeping the last post counter low.The project is a whole mess with different hardware/firmware versions going on but no tracked history and no downloads for schematics and firmware for older revs.I already tried contrast down/up. There is nothing. There is also no data on the serial coming from µC to the LCD. No response to button clicks.How can I check if the µC is alive and/or programmed?Thanks

author: ace1903
author_rank: Regular Contributor
timestamp: May 20, 2018, 10:57:46 am
content: Difficult to know without knowing which version you have.In latest firmware there is USB stack initialization before LCD init.Have you tried to connect to PC?Post pictures from your device ,maybe someone will find something unusual.How you checked that component placement is ok if you have not schematics?How battery voltage divider is configured? Did you tried to vary supply schematics?

author: OE2WHP
author_rank: Regular Contributor
timestamp: May 20, 2018, 11:09:00 am
content: According to the pcb, mine is revision 2.61.Yes I tried to connect it to the PC but no joy. The pc doesn't recognize a usb device.I checked component placement by the parts list that came with the kit and the silk screen on the pcb. I also found the schematics that came with the kit but it's rev 2.60 and the pcb says rev 2.61. As far as I found, the only difference is in the HV section not longer using a transformer.attached is the schematics.EDIT: added picsThanks

author: ace1903
author_rank: Regular Contributor
timestamp: May 20, 2018, 12:03:12 pm
content: It is difficult to see if L2 is missing on the board.There should be transformer according schematics.I think that L3 should be placed where L2 is(cant see if L3 has 2 or 4 wire ends).Can you take a picture of back side of LCD. Are there some soldering bridges for setting I2C address?Can you check if there is activity during power up on SDA and SCL(with scope or logic analyzer)?

author: OE2WHP
author_rank: Regular Contributor
timestamp: May 20, 2018, 01:05:13 pm
content: L2 is on the left of the LM358.L3 is not a transformer; It has two pins.The T3 BS170 Mosfet as the switching element for the HV has been changed to a MPSA44 high voltage NPN transistor. as I said, the HV section is different between Rev 2.60 and Rev 2.61. The controller part seems to be the same circuitry on both versions.SDA & SCL show no activity whatsoever.Here are some better pictures:Thanks

author: ace1903
author_rank: Regular Contributor
timestamp: May 20, 2018, 01:21:02 pm
content: Seems that R3 and R4 are not installed.Those are pull up for I2C bus and without them micro can not communicate with display.Install both resistor and check with scope if there are pulses.

author: OE2WHP
author_rank: Regular Contributor
timestamp: May 20, 2018, 01:45:13 pm
content: I have not populated them, because the assembling instructions told different. R3/4 should only be populated if a native I²C display is used but I use one with an expander. I assume, those two resistors are on the expander board.Thanks

author: ace1903
author_rank: Regular Contributor
timestamp: May 20, 2018, 01:53:37 pm
content: I can't see them near the PCF8574.Add two 4K7 if you have and it won't hurt if there are installed resistor on expander board.You can check with multimeter levels on SCL and SDA. I2C idle level is high and there should be near 5V on both lines.

author: tsman
author_rank: Frequent Contributor
timestamp: May 20, 2018, 02:04:16 pm
content: https://www.elektroda.pl/rtvforum/topic3387825.htmlappears to have the schematics + source for your v2.61. I've not registered to try to download though. You can see a badly formatted copy of the source inside the RAR file athttps://files.elektroda.pl/861440,radkit-v2.htmlas well

author: OE2WHP
author_rank: Regular Contributor
timestamp: May 20, 2018, 02:44:05 pm
content: I thought, that won't help because there was nothing on SDA and SCL. Not with the DMM nor with the scope. What could a pull down resistor do when there is nothing to pull down? But for peace of mind, I threw in the two 4k7 that you suggested and guess what?Thanks a lot for your help! Maybe you could explain to me, why it didn't run without those 2 ressis?ThanksEDIT:tsman, thanks I'll take a look at it.

author: tsman
author_rank: Frequent Contributor
timestamp: May 20, 2018, 03:02:20 pm
content: Quote from: OE2WHP on May 20, 2018, 02:44:05 pmYou added two pull up resistors.

author: OE2WHP
author_rank: Regular Contributor
timestamp: May 20, 2018, 03:21:59 pm
content: Quote from: tsman on May 20, 2018, 03:02:20 pmOMFG..... you are right. At some stage of the troubleshooting process I memorized them as connected to ground, not to Vcc

author: tsman
author_rank: Frequent Contributor
timestamp: May 20, 2018, 03:48:11 pm
content: https://nurdspace.nl/images/e/ea/Rad%40H_V2.61_schema.pdfis the v2.61 schematic. As you already discovered, it is nearly identical except for some changes in the HV section.