Anyone feel like troubleshooting a board layout? This is an ESP carrier board with an ATTINY 85 on it for dedicated hardware PWM. The problem is, the Tiny isn’t recognized by the SPI programmer through the 6 pin header.
I’ve made sure there’s no solder bridges on the chip, and also tried removing the two 4.7k pull-up resistors (r2 and r4) on the SDA and SCL lines, as SCL is also used by SPI as the clock line. I verified proper voltage on the supply pins, and verified continuity to all pins. I must be missing something simple?
The ESP module has not been placed yet, just the T85, the voltage regulator and the passive components.
We could ask the expert, Mr CS80 if he can spare the time for quick oggle. Paging @Scott_Rider to the bananaphone. ^^!
@Arve_Lotveit pin 8 is vcc with the 0u1 cap, pin 4 is gnd next to the via. Pin 1 rst is on the bottom right, with a diagonal track running to the 10k resistor. Thank you for double checking for me 
The “top” of the chip is facing the 6 pin header, where the ic2 label is. Pin 1 on the right, pin 8 on the left.
Turns out the board is fine, one of the six pins in my programming cable was making good enough conduction to detect the chip but not enough to program it. Woo!
@Gordon_McLellan Aren’t you a lucky bunny.
Is it just me or are your green circles all mis-aligned? eg, the 2x3 in the middle it looks like the middle 2 are higher up. And the 1x6 on the top right is all over the place.
The most important question remaining is how gloriously will it explode?
@Bunny_Evans they are slightly misaligned… Something from the Sparkfun library, designed to help hold parts in place while soldering.
The 1x6 is a screw up, it’s actually a 1x4 and a 1x2 next to each other, off just enough that 6 pins won’t fit. No need really, two pins on the end are briefly shorted during power on to enter bootloader mode.
@Gordon_McLellan Oh, how weird. I’ve never done anything PCB level…
I’m surprised you need an attiny85 for PWM, the esp8266 can do that easily enough for you. On a related note, one of my designs has an attiny85 as well (for extended deepsleep), but I wired its programming pins directly to the ESP. Effectively allowing me to OTA the attiny ^^
@Pauline_Middelink I got lazy. The T85 is running hardware pwm at 20khz for a motor controller. It was easier offloading that task rather than figure out how to do it on the ESP without wasting a lot of cycles in a timing loop. I am interested in using a tiny for extended deep sleep, do you have more information published?
@Gordon_McLellan Sadly not really documented or released. In short my attiny mimics an i2c device towards the ESP using 2 of the 4 SPI pins (mainly because I got lazy as well, didn’t want to setup a SPI endpoint for the attiny). The attiny runs a 16-bit timer, (based off the 1s watchdog timer) which when it expires resets the ESP. It also monitors the reset pin, so it can disable itself - say because you reprogram your ESP. Bit sad if the timer goes off in the middle of this reprogramming… So lots of interrupt programming, all to let the attiny sleep and consume 10uA. Together with the ESP in deepsleep I finally can count my battery life in months instead of days
