Chinese Attiny85 - doesn't upload - Page 1
Forum section: electronics / repair

author: kalel
author_rank: Frequent Contributor
timestamp: October 16, 2017, 05:09:28 pm
content: One of those attiny boards with flashed bootloader isn't working. I have two, and one does work and does upload when USB is plugged in.I have installed the Digispark drivers.Since one works, and the other doesn't, I assume a possible hardware issue. I have checked voltages of the not working one.5V - GND 4.7vVIN - GND 4vP5 - GND 4.4vP3 - GND 2.9v(those are the only two with significant voltage)Power LED is on.I don't have a scope, logic analyzer, or external programmer. Any ideas of what else to check?

author: edavid
author_rank: Super Contributor
timestamp: October 16, 2017, 05:16:26 pm
content: Are you sure it has the bootloader? I have bought some of these that arrived blank. Others from the same seller were fine.

author: kalel
author_rank: Frequent Contributor
timestamp: October 16, 2017, 05:37:11 pm
content: Both of the units (working and not working) are from the same seller.Is it possible that some come with the bootloader and some not?I can't be sure if it has the bootloader, since I don't know a way to verify.Maybe the bootloader has a specific start up procedure that could be seen or measured? Well, with a multimeter.

author: Armadillo
author_rank: Super Contributor
timestamp: October 16, 2017, 05:37:47 pm
content: Reinstall the bootloader.http://digistump.com/wiki/digispark/tutorials/connectingEdit: Read the troubleshooting inside.

author: kalel
author_rank: Frequent Contributor
timestamp: October 16, 2017, 05:52:01 pm
content: Quote from: Armadillo on October 16, 2017, 05:37:47 pmDoes it mention somewhere how the bootloader is reinstalled (that's after taking a look)? Is this possible without an external programmer? Unfortunately I don't have one.

author: edavid
author_rank: Super Contributor
timestamp: October 16, 2017, 05:53:34 pm
content: Quote from: kalel on October 16, 2017, 05:52:01 pmYou can use an Arduino, but if you don't have one, or don't want to bother, just ask for a refund.

author: kalel
author_rank: Frequent Contributor
timestamp: October 16, 2017, 06:05:30 pm
content: Quote from: edavid on October 16, 2017, 05:53:34 pmToo late for a refund. It's probably not worth buying a programmer for this.I have an Arduino UNO clone, but I am a novice.With the very limited information, is there some confidence that the likely cause is the bootloader missing or not being flashed properly, and not a hardware issue?In any case at least it's very affordable.

author: ebclr
author_rank: Super Contributor
timestamp: October 16, 2017, 07:30:00 pm
content: Just plug USB without any HUB, This product isn't Hub friendly, try a port on the computer without a HUb

author: kalel
author_rank: Frequent Contributor
timestamp: October 16, 2017, 07:44:59 pm
content: Quote from: ebclr on October 16, 2017, 07:30:00 pmI'm not using a hub, but it is on front panel. I could try motherboard directly, but the other unit works (1 out of 2).

author: stj
author_rank: Super Contributor
timestamp: October 17, 2017, 10:04:46 am
content: look very closely at the soldering,i have read that some people have had poor soldering on similar boards using STM controllers.to be specific, your looking at the soldering on the usb socket.

author: kalel
author_rank: Frequent Contributor
timestamp: October 17, 2017, 10:31:20 am
content: Quote from: stj on October 17, 2017, 10:04:46 amIt's kind of hard to see or even picture the MicroUSB joints properly. Right next to other tiny components too.Some images:Another note is that I do get "A request for the USB device descriptor failed." in device manager. But, from what I've read somewhere, this can happen with healthy units too depending on what code they are executing.