Bluetooth Esp8266 Sketch upload and serial monitoring/debugging through HC 05
What Is Needed
Any variation of ESP-01 ESP8266 $1.64 Esp8266 01 S have blue LED pin on pin2, Previous versions have blue LED on pin1.
HC-05HC05 RF Wireless Bluetooth , $2.59. A 6 pin HC 05. This needs to be programmed to 115200 bautrate with AT commands. See my post Use Nodemcu To Program HC 05 if you have a Nodemcu or another programmer. This can do- AT+UART=115200 Enter. AT+POLAR= 1, 0 is needed to pull NPN transistor Base pin high when sketch is done uploading to reset Attiny.
ATTINY85-20PU ATTINY85 DIP, $1.07 Attiny is programmed with sketch provided below. There is a lot of information on web for that. Attiny pins are thin and short, additional short pieces of wire are soldered to each pin if using regular female headers for better contact. If using dip socket this is unnecessary.
*2x 10k resistors (0603 smd), these are tiny but not that hard to solder.
*Round dot on Attiny right upper corner signifies location of Attiny on PCB in conjunction with two white lines
*NPN Transistor S8050, any NPN transistor should work. This resets Attiny when Sketch upload completes.
*0.1uf 104 disk capacitor, the one in photo, left top works well too.
*Gpio_0 and 1 are broke out on PCB.
*Can add a terminal for power.
*Toothbrush helps clean PCB after soldering.
Note: Some items can be salvaged from old electronics for free. Any old electronics might have these parts
Total Cost: Roughly $7. Some items can be salvaged from old electronics and other may be laying around. Shopping online might yield lower prices.
All components are soldered on PCB except HC 05, Esp8266 and Attiny, these can be removed from board. There is a silkscreen on PCB board showing what parts goes where. Using a stiff toothbrush to gently clean a soldering job helps remove tiny balls of solder that create a short and renders board useless!