Nrf51 UART example code has problem!

[chtsai]

Dear Sir,

Here I test the ble_peripheral example "ble_app_uart" (Softdevice 8.0) with Kail MDK ARM 5.20 environemt on the PAC10028A board.

I found it's not stable and alwasy will happen error (auto disoccnect) after continue notification a while.

Here I use the nRF Connect/MCP APP in my android phone. the UART I/F is connected to PC(Win10) and run a uart tool (Serial port utility) I use it to send 20 bytes message ex. "0123456789001234567890" to the PCA10028 and it will notify to MCP the received message. It works for trying serveral time but always fail (auto disconnect) after send many times. I set the 1 second repeat action(send 20 bytes) in the tool still has same problem no need wait too long(within 30 seconds) will see the situation. I chang the repeat sending period to 5 seconds and modify default baud rate to 9600 bps(FW) still has same problem.

1. Here we have BLE UART bridge applications, and need good and stable solution. It is easy to duplicate the situation, could help try, find and fix the root casue of the example code.

2. Our application should need higher throughput by UART, I know the BLE 4.0 ,4.1 has limitation (20 bytes, package delay time etc.) but Is it possiable to achieve higher if upgradte to BLE 4.2 , and Nordic is ready to provide BLE 4.2 more data bytes package to help our applcaition ?

Thanks your help!

[Stefan Birnir Sverrisson]

Hi

You are correct, the ble_app_uart example code has a problem. When throughput gets high, the application will assert. There is a preliminary solution described in my answer here, which contains an improved ble_app_uart code.

[chtsai]

Dear Stefan,

Thanks the quickly response, I read some post and it seems the issue still on going ? no final example code available ? you mentioned that you have some improvement in it what's the final result/conclusion ? In my case I just repeated transfer 20 bytes every one seconds , it should be enough time and should not get BLE_ERROR_NO_TX_PACKETS result in theory, but it happened which means has problem, skip put new data into stack if not success seems to avoid the problem not fix the problem in deep inside. Could help provide new "uart_app_uart" sample files (I use SD110 8.0 ) so I can test here to check if it ok for such simple testing case.

Another question is about increase throughput by using the BLE 4.2 large data package (> 20 bytes) , do you know can use on nRF51 device just update FW/SW to support BLE 4.2 is ok or need use new chip such as NRF52 ? any document, post to teach user how to upgrade to BLE 4.2 ?

Thanks

[Stefan Birnir Sverrisson]

Hi chtsai

Did you read the updated answer from 18.8.2016? Example is there, also brief description, compatibility, and conclusion on throughput measured.

If you are sending only one packet per second, that should however work fine with the standard ble_app_uart example. What is the reason for the disconnect? Do you see any error code returned? To figure out how to debug, look at these threads 1 2

BLE_ERROR_NO_TX_PACKETS means that no softdevice buffers are available. This error message is totally normal to get when you are pushing packets to the softdevice faster than the softdevice can send the packets over BLE. Then you should wait until some BLE packets have been sent and softdevice buffers become available again.

The data payload extension of BLE 4.2 has not been implemented yet into S130, but most likely soon.

[chtsai]

Dear Stefan,

1. Here I clearified my case it's different , no error code just restart but I found the reason, my uart adapater(usb2uart) connect to PC has problem, after change another one (different brand) not exist the situation, I don't want wast time to check why this usb2uart adapater has problem.

2. I used the BLE_EVT_TX_COMPLETE event to send arrived UART RX data should be no BLE_ERROR_NO_TX_PACKETS error. Is it still exist problem with higher throught according your experience ? (115200bps ok ?) in your experiment ( can up to 128Kbps).

3. BLE4.2 can also update in nRF51 , no need to change chip to nR52 right ?

Thanks

[Stefan Birnir Sverrisson]

Ok, Im glad that you figured out the problem.

The modified ble_app_uart example on the linked thread should not assert. You can select any UART BAUD rate and any BLE throughput setting, it will attempt to move data from UART to BLE as fast as it can. When UART fifo is full, the CPU will stop extracting data from the hardware UART buffer, which will make the UART set the RTS high and stop the UART peer device from sending more data. When softdevice buffer is full, the CPU will wait until BLE_EVT_TX_COMPLETE event is received or when BLE services are enabled.