Helpful ReplyHot!RN4870 %Unknown Device% meaning

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tunelabguy
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Re: RN4870 %Unknown Device% meaning 2018/02/07 19:08:48 (permalink)
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That is good to know.  I assume this won't fix the problem after it has occurred, but fortunately I have only had the problem with one device.  In the future, as long as I can manage to flash 1.28.3 before the damage happens, it should be OK after that in the field.

Robert Scott
Hopkins, MN
 
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connelky
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Re: RN4870 %Unknown Device% meaning 2018/02/12 10:25:51 (permalink)
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As others have mentioned, this is a firmware issue on the RN4871, a field engineer who I spoke to confirmed this. Upgrade the firmware to v1.28.3, or whatever latest is on this link:
http://www.microchip.com/wwwproducts/en/RN4871
Go to software section and you will see the updater tool and the firmware. Follow directions to update, very easy. You will need a serial port and a terminal setup the same way for interacting with the module, and will need to place the mode pin (pin 16 I believe) on the RN4871 in the programming state.
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costa
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Re: RN4870 %Unknown Device% meaning 2018/02/14 11:00:16 (permalink)
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Great to read about problem fixing
After this fix, is still necessary the reset chip, such as MCP112 ?
Where are talking about very cost sensitive products
post edited by costa - 2018/02/14 11:01:23
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connelky
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Re: RN4870 %Unknown Device% meaning 2018/02/14 11:43:45 (permalink)
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costa, based on the explanation I received the reset chip should not be necessary. The issue was when the device was in the middle of writing to some memory location, if the voltage dropped below some level the address to write to would become 0x00, and then the next few registers at that location would get destroyed. There is sensitive calibration information and such at that location. The new firmware saves these registers in multiple locations and then checks those registers on boot up and restores them if they have been altered.
 
Furthermore, one of the devices we had bricked even with the voltage monitor so I don't think it was actually helping this issue.
 
But I would say in general, you should make your design such that the Bluetooth module and any MCU's or other digital components shutdown if the voltage is browning out. All that stuff is going to go into an unknown state at lower voltage.
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RISC
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Re: RN4870 %Unknown Device% meaning 2018/02/14 15:36:44 (permalink)
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Hi,
Reset chip & 47uF capacitor are an "insurance" against flash corruption.
In any design (including flash microcontroller) where the internal flash can be reprogrammed, it is a good design pratice to use the internal BOR and a capacitor to lessen / annihilate the risk of flash corruption.
Even with the new firmware patch, I would personally not remove the reset chip and the capacitor which contribute to the system robustness...
FMHO, there is nothing more damaging to a company's reputation than products which fail in the field so the extra cost is worth it.
Regards
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XgN
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Re: RN4870 %Unknown Device% meaning 2018/04/15 15:13:01 (permalink)
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Hello,
 
I have two RN4871 modules and they have the same problems like Unknown Device, MAC set to zeros, presenting themselves like 4870 modules (SW,0C,04 command not working, but 4870 SW,07,04 is working) etc. Maybe anyone has found the solution? Tried reflashing the latest v1.28.3 firmware many times, nothing changed. Tried flashing v1.18 firmware modules don't work at all with it. All ideas appreciated!
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