- Tue Mar 22, 2016 7:57 am
#188821
Hello SparkFun engineers! It seems there is a problem with the battery charging circuit on the Purpletooth Jamboree. It was driving me nuts. All versions of firmware failed to provide any feedback over SPI of charging status. Most notably, the error with firmware 6.0.33 was "BATTERY_STATUS CHARGER DISABLED_ERROR". I had the "BATT_CONFIG" setting enabled as well.
So, I took a look at the schematic and compared it to the BC127 datasheet from Blue Creation. After much head scratching I found one critical mistake.
The Purpletooth Jamboree has V_USB, V_FTDI and V_BAT all feeding V_IN through diodes. Then, you have V_IN feeding the VCHG pin on the BC127. According to the Blue Creation spec, the VCHG pin is supposed to connect directly to the external power supply (ie. V_USB or V_FTDI).
The problem this creates is that the VCHG pin is always seeing a voltage. When the BC127 sees a voltage on the VCHG pin it thinks the charger is connected. When no charger is connected the VCHG pin is supposed to see 0V.
So, I cut the trace between V_IN and the VCHG pin (leaving VCHG connected to the emitter of the PNP transistor) then soldered a jumper from the VCHG/E trace to the V_USB (to the anode of the diode).
Now it works! When I connect the USB power the "BATTERY_STATUS" shows "BATTERY_STATUS CHARGER IN_PROGRESS" and when it's disconnected it shows "BATTERY_STATUS CHARGER DISCONNECTED". It also shows the battery voltage in both cases.
Do I get a finder's reward? Do I get a free Purpletooth Jamboree 2.0? LOL!
Thanks,
Jeff
So, I took a look at the schematic and compared it to the BC127 datasheet from Blue Creation. After much head scratching I found one critical mistake.
The Purpletooth Jamboree has V_USB, V_FTDI and V_BAT all feeding V_IN through diodes. Then, you have V_IN feeding the VCHG pin on the BC127. According to the Blue Creation spec, the VCHG pin is supposed to connect directly to the external power supply (ie. V_USB or V_FTDI).
The problem this creates is that the VCHG pin is always seeing a voltage. When the BC127 sees a voltage on the VCHG pin it thinks the charger is connected. When no charger is connected the VCHG pin is supposed to see 0V.
So, I cut the trace between V_IN and the VCHG pin (leaving VCHG connected to the emitter of the PNP transistor) then soldered a jumper from the VCHG/E trace to the V_USB (to the anode of the diode).
Now it works! When I connect the USB power the "BATTERY_STATUS" shows "BATTERY_STATUS CHARGER IN_PROGRESS" and when it's disconnected it shows "BATTERY_STATUS CHARGER DISCONNECTED". It also shows the battery voltage in both cases.
Do I get a finder's reward? Do I get a free Purpletooth Jamboree 2.0? LOL!
Thanks,
Jeff