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EVM tx kit not pinging

Other Parts Discussed in Thread: BQ500211EVM-045, BQ500211

I'm having some difficulty getting the EVM kits to work

I'm using a bq500211evm-045  for the TX and a bq51013evm-725 for RX

First of all, there's a 3.3v buck regulator on board that wasn't working.  The enable line to it had a sawtooth waveform and was never starting up.  I shorted it to 5V and momentarily, and now it works fine, I'm not sure what to make of that, but... okay.

It's my understanding that the TX device should be pinging the TX coil once in a while to determine if there's an RX device coupled in.  If I probe the TX coil, I see some chatter on the line at startup, but then there's nothing.  In order for me to get the RX evm to receive power, I must put it in place, and THEN turn on the power.  If I try to replace RX evm, or place it on the TX coil after I've turned on the power, nothing happens.  The only thing I've changed on the TX board is the LED_MODE resistor to a 48.7K so that the status LEDS are both on when the device is in standby mode.  

Has anyone seen this before?

  • I'm still looking for an answer to this... anyone have an idea as to why the TX side is not pinging?

  • Chris

    Try configuring the unit to operate without the MSP430----Install a 0 ohm resistor in R15 spot.  This will prevent the device from going to sleep, the saw tooth at EN should stop and it should be high.

    Check for a Pulse at pin 12 or 13 every 400mS.  Every 5 Sec the Digital ping should occur.

  • Thanks Bill, That seems to work.  I'm a little confused as to what's going on here though.

    According to the BQ500211 datasheet in the Low Power Supervisor section, the MSP430 should still be waking up the chip to do digital pings.  Is the sleep command being sent over SPI?  I can't find any connection between the MSP430 and any reset or sleep pins on the BQ500211.

  • The MSP430 will hold info from the BQ500xxx during sleep, acts like memory.  To reduce stand-by power the voltage to bq500XXX is removed during sleep, every 400mS.  But when power is removed all info on operating conditions are lost.

    Sleep sequence:

    1.)     Prepare to go to SLEEP, send operating conditions to MSP430

    2.)     Pulse SLEEP pin High, Q4 turns on discharges C22, EN goes low—3.3V OFF.

    3.)     C22 recharges though R25

    4.)     After ~400mS EN goes high --- 3.3V ON

    5.)     BQ500XXX wakes up and pulls operating conditions from the MSP430

    6.)     Analog ping is sent to TX coil then COMM signal is checked.

    7.)     If  amplitude decreased by 10% then go to digital ping---Look for RX on TX coil

    8.)     If less than 10% then go back to sleep

    During normal standby operation you will see a sawtooth waveform at the EN pin of the 3.3V LDO.

     

    At power on digital pin is send a couple of time.

    Also digital ping is sent every 5 sec.