Some of our first v2 PCB customers found that PIC doesn’t work normally, and LCD backlight flicks every 2-3 seconds. We made some internal investigations and found that around 30% of first batch of PIC microcontroller come to us with programmed code section, but not-programmed configuration section. As a result, watchdog timer on PIC was active (this is default option in PIC12F1840), and it reset PIC every 2-3 seconds that leads to flicks of LCD backlight. If you have such case, please proceed as follows:
If you have access to Microchip PicKit3 programmer, then please re-program HEX file to PIC controller (HEX-file is available together with sources in Support/Sources/PCBv2 section). The simplest way to re-program is to solder wires from PicKit right over the PIC in circuit (remove our PCB from motherboard). Here is connection diagram:
|PicKit3 pin #||PIC pin #|
|2||1 (or central pin of power IC)|
|3||8 (or pin 1 of power IC)|
Here is command line for programming (supposed that hex file is in the C:\ root):
PK3CMD.exe -P12F1840 -E -M -Fc:\backlight_v1.hex -V3.3
All new orders shipped since starting of this week come with correctly programmed PIC and do not require any changes. Now we do PIC programming internally in our company to avoid problems like this in the future.