UBB pattern generator ===================== ubb-patgen uses the MMC controller in the Ben Nanonote to send a digital pattern on the DATx lines of UBB. All four DATx lines can be used. The maximum output rate is 56 MHz, the maximum pattern size is 8128 nibbles. ubb-patgen can also output a clock of arbitrary duration on the CLK signal. The frequencies available for the pattern and the clock signal range from 41 kHz to 56 MHz. A map can be found here: http://downloads.qi-hardware.com/people/werner/ubb/ben-mmc-clk.png Frequency list -------------- # ubb-patgen shows the available frequencies in ascending order and the corresponding MMC clock divider and bus clock tap settings. # ubb-patgen -q does the same but shows only the frequencies (in Hz) as floating-point numbers. Frequency selection ------------------- # ubb-patgen -f 17000000 # ubb-patgen -f 17M # ubb-patgen -f 17MHz all look for the available frequency closest to 17 MHz and print its value in Hz. Appending a + limits the search to frequencies greater than or equal to the specified value. Similarly, - searches for frequencies that don't exceed the specified value. Examples: # ubb-patgen -f 10MHz 9882352.941176 # ubb-patgen -f 10MHz+ 10500000.000000 # ubb-patgen -f 15M 15272727.272727 # ubb-patgen -f 15M- 14000000.000000 Note that this form of invocation only searches the frequency table but does not produce any output on UBB. ubb-patgen warns if the selected frequency does not match the requested frequency, e.g., # ubb-patgen -f 100kHz bus clk = 100.962 kHz (+0.96%) This warning can be suppressed with the option -q. The frequency can also be specified as the cycle time with the option -i: # ubb-patgen -i 10us The meaning of an appended + or - changes here, e.g., 10us+ selects a slower clock (producing an interval of at least 10 us). The options -F and -I work like -f and -i but also allows frequencies that may exceed the hardware's capabilities. As a consequence, the MMC controller may hang. Clock output ------------ # ubb-patgen -c outputs a clock on CLK. The default is 1 MHz and can be changed with the option -f. ubb-patgen exits and leaves the clock running. To wait for a while and clean up on exit, add the delay in seconds, e.g.: # ubb-patgen -f 500kHz -c 10 The delay can be followed by "m", "u", or "n" for the respective multiplier. Furthermore, it can end with an optional "s". Note that the minimum time ubb-patgen actually spends generating a clock will typically be in the order of several milliseconds. To stop the MMC bus clock, run # ubb-patgen -c 0 Pattern output -------------- # ubb-patgen 0110 first sets the DATx lines to 0, then outputs a 1 bit on DAT0 for two clock cycles, and returns DAT0 to zero. Each digit is a nibble representing the four DATx lines, with DAT0 having the value 1, DAT1 2, DAT2 4, and DAT3 8. The repetition of a nibble can also be expressed by following it with the number of repetitions in curly braces, e.g., # ubb-patgen 01{2}0 The options -f and -q work as usual. The clock is normally not output but can be activated with the option -C. Note that the clock output is not continuous in this case. The pattern can be read from a file. All whitespace is ignored and so are comments beginning with #: # cat <pattern-file 1 # idle state is high # send two characters in RS232 format 0 00010010 1 # "H" 0 10010110 1 # "i" 0 10000100 1 # "!" 0 10110000 1 # CR 1 # return to idle (high) EOF # ubb-patgen -f 115.2k pattern-file If a file with the same name as a pattern exists, ubb-patgen will try to load that file. This can be prevented with the option -p. If only some of the DATx lines should be used for pattern output, the option -m MASK can be used to leave the unused lines in their previous state. MASK is a value in C syntax. Only lines whose bit is set are used for pattern output. External trigger ---------------- ubb-patgen normally sends the pattern immediately. This can be delayed by waiting for an external trigger with the option -t. # ubb-patgen -t 0 0f0 configures CLK as an input, waits for it to become zero, and then outputs the 010 pattern. If CLK is already zero, ubb-patgen will send the pattern immediately. Likewise, -t 1 waits for CLK to become 1. -t cannot be used with the -C option. The trigger can also be a sequence, e.g., -t 01 would first wait for CLK to become zero (if it isn't already), then wait for it to become one. ubb-patgen usually starts the pattern about 2-10 us after the trigger, but this can be delayed by other system activity. An extra delay can be added with the option -w, e.g., # ubb-patgen -t 0 -w 1s 010 The trigger signal can be debounced with the option -d, e.g., # ubb-patgen -t 0 -d 100us 0f0 This accepts the trigger only after it has been zero for at least 100 microseconds. If the trigger is a sequence, debouncing is applied at each step. Timeline details ---------------- timing.fig illustrates the various steps of pattern generation. A PDF of the diagram can be found here: http://downloads.qi-hardware.com/people/werner/ubb/patgen/timeline.pdf CLK is the clock output if selected with -C. DATx are the data lines, with the value of DAT0 shown. TRIG is the trigger input. Note that in real life, the TRIG/CLK line can only act either as trigger input or as clock output but not as both at the same time. The pattern we send is 0110110. We trigger on TRIG being low, with a debounce time of nominally about one pattern clock interval, and some post-trigger delay. After ubb-patgen starts, it first processes the command-line options and arguments, then initializes the pins. DATx are set to the value of the first pattern. Next, ubb-patgen sets up the MMC controller, makes it send a command, receives a pseudo-response, and begins sending copies of the first pattern on DATx. These copies are necessary to get past the start bit and to make the MMC controller drive DATx to known levels. Once this pattern has been sent, we switch DATx to GPIO. When this is done, ubb-patgen waits for the trigger. In this example, we first ignore a glitch and then detect a correct trigger value. Note that the effective debounce period is usually longer than specified, since other system activity can delay the sampling. Once ubb-patgen has triggered, it starts the DMA controller and thus begins sending the pattern. The first cycle (marked with a question mark) is an uncommanded repetition of the first pattern (apparently there is a buffer stage in the MMC controller) followed by the entire sequence, first to last pattern. At the end, several copies of the last pattern may be sent in order to reach the transfer size of the DMA controller (32 bytes). ubb-patgen then ensures that all data has left the MMC controller, switches DATx back to GPIO, and exits.