Problem using UART and radio in ESB mode on nRF24LE01.

RE: Problem using UART and radio in ESB mode on nRF24LE01.

mr_creosote — Wed, 22 Mar 2017 07:12:32 GMT

here's some example code i'm using.

//-------- UART begin
IP0 = 0x10;	// make uart higher priority than RF.
IP1 = 0x10;	// make uart higher priority than RF.
P0DIR = (P0DIR & ~0x08) | 0x10; // bxxx1-0xxx
hal_uart_init(UART_BAUD_38K4); 
while(hal_clk_get_16m_source() != HAL_CLK_XOSC16M);
...
...
...
//-------- do some UART stuff now. turn off RF IRQ
RF = 0; // disable RF IRQ
printf("print one thing here.");
printf("print another thing here.");
RF = 1; // enable RF IRQ

RE: Problem using UART and radio in ESB mode on nRF24LE01.

Håkon Alseth — Thu, 02 Jan 2014 10:36:41 GMT

Hi Adam,

Happy new year to you!

Your understanding is correct. The IP0/IP1 have a reset value of 0, meaning all interrupts have the same priority. This is as intended, as it is up to you which interrupts you use and how to use them.

The IPx register is located at a 16 bit address, but the value inside the registers are 8 bit. You can use "sbit", similar to what is done with the GPIOs (P00 for instance), but this register is mapped directly without sbit. Setting the register can be done like this: IPx |= (1 << BIT_x); // set bit IPx &= ~(1 << BIT_x); // Clear bit

BR Håkon

RE: Problem using UART and radio in ESB mode on nRF24LE01.

Adam Czezowski — Wed, 25 Dec 2013 07:53:07 GMT

Aha one more thing. IP0 and IP1 addresses are not located on 8-bit boundary hence sbits can not be used in Keil C51. This is very strange as in the manual they clearly have bit-per-bit settings. Omission on 8051 implementer or just annoyance?

Cheers

Adam

RE: Problem using UART and radio in ESB mode on nRF24LE01.

Adam Czezowski — Wed, 25 Dec 2013 07:34:43 GMT

Hi Håkon,

Merry Christmas! Thank you for explanation of what is going on in my ISR and of the dead-lock condition. Since then I am tinkering with IP0 and IP1 registers. When I read content of these two register upon power-up they all are 0. Does this mean that after power is supplied to nrf24LE1 the default priority of all priority groups is at its lowest level 0 that is that all interrupts are treated equally?

Is this normal and desired? I am coming from java programming background and still consider myself as newbie embedded programmer.

Regards

Adam

RE: Problem using UART and radio in ESB mode on nRF24LE01.

Håkon Alseth — Thu, 05 Dec 2013 10:06:15 GMT

Hi Adam,

The UART print routine will call on function "hal_uart_putchar", which again relies on the UART0_ISR. The hal_uart library is a blocking library, meaning it uses while-loops that needs UART0_ISR function to handle.

When you are triggering an interrupt from another interrupt with the same priority, this will give you a deadlock-situation. This is the situation:

print function called from NRF-interrupt
print function will trigger UART-interrupt
print function will loop until UART-ISR is one
Cannot enter UART-ISR, as you are currently processing NRF_ISR.

You have two ways of avoiding this:

Call print-routines only from main-context
Set a higher priority on UART interrupt (using IP0 and IP1 registers)

Best regards Håkon

RE: Problem using UART and radio in ESB mode on nRF24LE01.

Bastiaan — Wed, 04 Dec 2013 22:20:21 GMT

Hi Håkon

sure they (ISR) should be kept short but I don't understand why my code dos not work in my case at all. I am sending packet of data only when I press a button on my RX side so in this case timing should not be a problem.

Are you aware of any other restrictions while in ISR?

Thanks you and Cheers

Adam

RE: Problem using UART and radio in ESB mode on nRF24LE01.

Guest — Wed, 04 Dec 2013 22:20:21 GMT

Hi Håkon

Are you aware of any other restrictions while in ISR?

Thanks you and Cheers

Adam

RE: Problem using UART and radio in ESB mode on nRF24LE01.

Håkon Alseth — Wed, 04 Dec 2013 13:53:25 GMT

Hi,

Calling UART prints from interrupt context is not recommended. Note that your UART baudrate is quite low (9k6), which then uses almost 1 ms to send one byte. When sending 10-20 bytes while in the NRF_ISR() routine, you will get a timing error if your PTX is sending at a high frequency. You normally want to keep ISR routines as short as possible.

Try using global flags and send UART prints in your main loop instead, and lower the frequency that you are pushing packets over the RF link (add a delay on the PTX side).

-H