Pin assignment of QFN40 on nRF52820 and nRF52833 is messed up

[Lukáš]

Hi,

we spent 2 days of debugging why our application doesn't work on new nRF52820 & nRF52833 in QFN40 package. And today, we found out that some of the pins have probably their name wrong. For example, on GPIO_0 peripheral, pin number 33 with the name P0.30 corresponds to the P0.28 and pin number 14 with the name P.014 corresponds to the P0.15. We were not able to drive pin numbers 1, 2,3, and 4. We followed the latest specification of these chips and we use NCS Zephyr v2.1.99.

Could you please confirm that current labeling is wrong? Or is there something that we overlooked?

Best regards,

Lukas

[bjorn-spockeli]

Hi Lukas,

Yes, it is correct that an application that is written for the nRF52833 will need to remap its GPIOs to run correctly on the nRF52820. The nRF52820 is pin-to-pin compatible ( except when it comes to the NFC and some analog inputs) with the nRF52833, but not drop-in compatible, so you need to remap the GPIOs. 

Please see the attached spreadsheet.

 nRF52833_nRF52820_QFN40_Pinout_Comparison.xlsx

Best regards

Bjørn

[Lukáš]

Hi Bjorn,

I know this is not your fault but I think it is inappropriate to send customers sample chips and don't provide the proper documentation. It cost us two days of work but could be prevented only by a brief mention of existing materials. Hopefully, Nordic will get this improved in the future.

Best regards,

Lukas 

[bjorn-spockeli]

Hi Lukas, 

the pin assignments of the nRF52820 and nRF52833 QFN packages are shown in the respective product specifications, i.e. 

nRF52833 QFN40 pin assignments

nRF52820 QFN40 pin assignments

I made the comparison sheet by copy and pasting the pin assignments from the Product Specifications. So the difference is documented. 

The nRF52820 Product Brief states that the nRF52820 5x5 mm QFN40 with 18 GPIOs is drop-in compatible with nRF52833 SoC. 

Drop-in compatibility is related to hardware and stating that the nRF52820 is drop-in compatible is correct as far as I can see since the same functions are available on the same pins (excluding the peripherals that have been removed on the nRF52820), see definitions below. 

A drop-in compatible device is a device which may be swapped with another without need to make compensating alterations to the system the device was a part of. The device will have the same functions available on the same pins, and will be electrically and thermally compatible. Such devices may not be an exact match to the devices they can replace. For example, they may have a wider range of supply voltage or temperature tolerances.

Pin-to-pin compatible devices share an assignment of functions to pins, but may have differing electrical characteristics (supply voltages, or oscillator frequencies) or thermal characteristics (TDPs, reflow curves, or temperature tolerances).

However, I agree that we could add a comment to the product brief stating that the allthough the pin functions are the same, the pin names on the nRF52833 are not identical to the ones on the nRF52820  and must changed in the firmware. 

I will report this internally. 

Best regards

Bjørn

[Lukáš]

Bjorn, the QFN40 pin assignment was added to the nRF52833 product specification 1.2 on 27th April. We have received samples from RSM on 8th April with information that 833 and 820 are pin-to-pin compatible. 

I am not complaining but it seems that RSMs should be better informed in this manner.

Lukas

[bjorn-spockeli]

Ok, was not aware that the QFN 40 pin assignments weren't added to the nRF52833 PS before April 27th.  Pin-to-pin compatibility is still correct, but in terms of software we should have mentioned that the GPIOs needs to be remapped if you want to run an application developed on the nRF52833 on the nRF52820. 

I will pass this on sales so that we communicate this more clearly in the future. 

Best regards

Bjørn